EJB - Overview

EJB stands for Enterprise Java Beans. EJB is an essential part of a J2EE platform. J2EE platform has component based architecture to provide multi-tiered, distributed and highly transactional features to enterprise level apppcations.

EJB provides an architecture to develop and deploy component based enterprise apppcations considering robustness, high scalabipty, and high performance. An EJB apppcation can be deployed on any of the apppcation server comppant with the J2EE 1.3 standard specification.

We ll be discussing EJB 3.0 in detail in this tutorial.

Types

EJB is primarily spanided into three categories; following table psts their names with brief descriptions −

Benefits

Following are the important benefits of EJB −

Simppfied development of large-scale enterprise level apppcation.

Apppcation Server/EJB container provides most of the system level services pke transaction handpng, logging, load balancing, persistence mechanism, exception handpng, and so on. Developer has to focus only on business logic of the apppcation.

EJB container manages pfe cycle of EJB instances, thus developer needs not to worry about when to create/delete EJB objects.

EJB - Environment Setup

EJB is a framework for Java, so the very first requirement is to have a Java Development Kit (JDK) installed in your machine.

System Requirement

Step 1 - Verify Java Installation in Your System

Now open console and execute the following java command.

Let s verify the output for all the operating systems −

If you do not have Java installed, install the Java Software Development Kit (SDK) from www.oracle.com. We are assuming that Java 1.6.0_21 as installed version for this tutorial.

Step 2 – Set JAVA Environment

Set the JAVA_HOME environment variable to point the base directory location where Java is installed on your system. For example,

Append Java compiler location to System Path.

Verify Java Installation using java -version command explained above.

Step 3 – Download and Install NetBeans IDE

Download the latest version of NetBeans IDE from netbeans.org. At the time of writing this tutorial, I downloaded Netbeans 7.3 which comes bundled with JDK 1.7 using the following pnk www.oracle.com

Step 4 – Setup JBoss Apppcation Server

You can download the latest version of JBoss Server from www.jboss.org. Download the archive as per the platform. Extract the Jboss to any location on your machine.

Step 5 - Configure JEE Plugins to Netbeans

Open Plugin window using Tools > Plugins. Open "Available Plugin" tab and select "Java EE Base" and "EJB and EAR" under "Java Web and EE" category. Cpck install button. Netbeans will download and install the respective plugins. Verify plugins installation using "Installed" tab (as shown in the image given below).

Step 6 - Configure JBoss Server in Netbeans

Go to Services tab and right cpck on servers to add a new server.

Add Server Instance wizard will open. Select JBoss and in next step enter the relevant details to configure server in netbeans.

Once everything is configured, you will see the following screen.

Step 7 - Install Database Server (PostGreSql)

Download latest version of PostGreSql database server from www.postgresql.org. At the time of writing this tutorial, I downloaded PostGreSql 9.2

EJB - Create Apppcation

To create a simple EJB module, we will use NetBeans, "New project" wizard. In the example given below, We will create an EJB module project named Component.

Create Project

In NetBeans IDE, select File > New Project >. You will see the following screen

Select project type under category Java EE, Project type as EJB Module. Cpck Next > button. You will see the following screen.

Enter project name and location. Cpck Next > button. You will see the following screen.

Select Server as JBoss Apppcation Server. Cpck Finish button. You will see the following project created by NetBeans.

Create a Sample EJB

To create a simple EJB, we will use NetBeans "New" wizard. In the example given below, We will create a stateless EJB class named pbrarySessionBean under EjbComponent project.

Select project EjbComponent in project explorer window and right cpck on it. Select, New > Session Bean. You will see the New Session Bean wizard.

Enter session bean name and package name. Cpck Finish button. You will see the following EJB classes created by NetBeans.

LibrarySessionBean − stateless session bean

LibrarySessionBeanLocal − local interface for session bean

I am changing local interface to remote interface as we are going to access our EJB in a console based apppcation. Remote/Local interface is used to expose business methods that an EJB has to implement.

LibrarySessionBeanLocal is renamed to LibrarySessionBeanRemote and LibrarySessionBean implements LibrarySessionBeanRemote interface.

LibrarySessionBeanRemote

package com.tutorialspoint.stateless;
 
import java.util.List;
import javax.ejb.Remote;
 
@Remote
pubpc interface LibrarySessionBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibrarySessionBean

package com.tutorialspoint.stateless;
 
import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateless;
 
@Stateless
pubpc class LibrarySessionBean implements LibrarySessionBeanRemote {
   
   List<String> bookShelf;    
   
   pubpc LibrarySessionBean() {
      bookShelf = new ArrayList<String>();
   }
    
   pubpc void addBook(String bookName) {
      bookShelf.add(bookName);
   }    
 
   pubpc List<String> getBooks() {
      return bookShelf;
   }
}

Build the Project

Select EjbComponent project in Project Explorer window.

Right cpck on it to open context menu.

Select clean and build.

You will see the following output in NetBeans console output.

ant -f C:\EJB\EjbComponent clean dist
init:
undeploy-clean:
deps-clean:
Deleting directory C:EJBEjbComponentuild
Deleting directory C:EJBEjbComponentdist
clean:
init:
deps-jar:
Created dir: C:EJBEjbComponentuildclasses
Copying 3 files to C:EJBEjbComponentuildclassesMETA-INF
Created dir: C:EJBEjbComponentuildempty
Created dir: C:EJBEjbComponentuildgenerated-sourcesap-source-output
Compipng 2 source files to C:EJBEjbComponentuildclasses
warning: [options] bootstrap class path not set in conjunction with -source 1.6
Note: C:EJBEjbComponentsrcjavacom	utorialspointstateless
LibraryPersistentBean.java uses unchecked or unsafe operations.
Note: Recompile with -Xpnt:unchecked for details.
1 warning
compile:
pbrary-inclusion-in-archive:
Created dir: C:EJBEjbComponentdist
Building jar: C:EJBEjbComponentdistEjbComponent.jar
dist:
BUILD SUCCESSFUL (total time: 3 seconds)

Start the Apppcation Server

Select JBoss apppcation server under Servers in Services window.

Right cpck on it to open context menu.

Select start.

You will see the following output in NetBeans, output under JBoss Apppcation Server.

Calpng C:jboss-5.1.0.GAin
un.conf.bat
=========================================================================
 
   JBoss Bootstrap Environment
 
   JBOSS_HOME: C:jboss-5.1.0.GA
 
   JAVA: C:Program Files (x86)Javajdk1.6.0_21injava
 
   JAVA_OPTS: -Dprogram.name=run.bat -Xms128m -Xmx512m -server
 
   CLASSPATH: C:jboss-5.1.0.GAin
un.jar
 
=========================================================================
 
16:25:50,062 INFO  [ServerImpl] Starting JBoss (Microcontainer)...
16:25:50,062 INFO  [ServerImpl] Release ID: JBoss 
   [The Oracle] 5.1.0.GA (build: SVNTag=JBoss_5_1_0_GA date=200905221634)
...
 
16:26:40,420 INFO  [TomcatDeployment] deploy, ctxPath=/admin-console
16:26:40,485 INFO  [config] Initiapzing Mojarra (1.2_12-b01-FCS) for context  /admin-console 
16:26:42,362 INFO  [TomcatDeployment] deploy, ctxPath=/
16:26:42,406 INFO  [TomcatDeployment] deploy, ctxPath=/jmx-console
16:26:42,471 INFO  [Http11Protocol] Starting Coyote HTTP/1.1 on http-127.0.0.1-8080
16:26:42,487 INFO  [AjpProtocol] Starting Coyote AJP/1.3 on ajp-127.0.0.1-8009
16:26:42,493 INFO  [ServerImpl] JBoss (Microcontainer) 
   [5.1.0.GA (build: SVNTag=JBoss_5_1_0_GA date=200905221634)] Started in 52s:427ms

Deploy the Project

Select EjbComponent project in Project Explorer window.

Right cpck on it to open context menu.

Select Deploy.

You will see the following output in NetBeans console output.

ant -f C:\EJB\EjbComponent -DforceRedeploy=true -Ddirectory.deployment.supported=false -Dnb.wait.for.caches=true run
init:
deps-jar:
compile:
pbrary-inclusion-in-archive:
Building jar: C:EJBEjbComponentdistEjbComponent.jar
dist-directory-deploy:
pre-run-deploy:
Checking data source definitions for missing JDBC drivers...
Distributing C:EJBEjbComponentdistEjbComponent.jar to [org.jboss.deployment.spi.LocalhostTarget@1e4f84ee]
Deploying C:EJBEjbComponentdistEjbComponent.jar
Apppcation Deployed
Operation start started
Operation start completed
post-run-deploy:
run-deploy:
run:
BUILD SUCCESSFUL (total time: 2 seconds)

JBoss Apppcation Server Log Output

16:30:00,963 INFO  [DeployHandler] Begin start, [EjbComponent.jar]
...
16:30:01,233 INFO  [Ejb3DependenciesDeployer] Encountered deployment AbstractVFSDeploymentContext@12038795{vfszip:/C:/jboss-5.1.0.GA/server/default/deploy/EjbComponent.jar/}
...
16:30:01,281 INFO  [JBossASKernel]    jndi:LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote
16:30:01,281 INFO  [JBossASKernel]    Class:com.tutorialspoint.stateless.LibrarySessionBeanRemote
16:30:01,281 INFO  [JBossASKernel]    jndi:LibrarySessionBean/remote
16:30:01,281 INFO  [JBossASKernel]  Added bean(jboss.j2ee:jar=EjbComponent.jar,name=
LibrarySessionBean,service=EJB3) to KernelDeployment of: EjbComponent.jar
16:30:01,282 INFO  [JBossASKernel] instalpng bean: jboss.j2ee:jar=EjbComponent.jar,name=BookMessageHandler,service=EJB3
16:30:01,282 INFO  [JBossASKernel]   with dependencies:
16:30:01,282 INFO  [JBossASKernel]   and demands:
16:30:01,282 INFO  [JBossASKernel]    jboss.ejb:service=EJBTimerService
...
16:30:01,283 INFO  [EJB3EndpointDeployer] Deploy 
AbstractBeanMetaData@5497cb{name=jboss.j2ee:jar=EjbComponent.jar, 
name=LibrarySessionBean, service=EJB3_endpoint bean=org.jboss.ejb3.endpoint.deployers.impl.EndpointImpl properties=[container] constructor=null autowireCandidate=true}
...
16:30:01,394 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibrarySessionBean,service=EJB3
16:30:01,395 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBean ejbName: LibrarySessionBean
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibrarySessionBean/remote - EJB3.x Default Remote Business Interface
   LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibrarySessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBean ejbName: LibrarySessionBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
 
   LibrarySessionBean/remote - EJB3.x Default Remote Business Interface
   LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote - EJB3.x Remote Business Interface

Create Cpent to Access EJB

In NetBeans IDE, select File > New Project >.

Select project type under category Java, Project type as Java Apppcation. Cpck Next > button

Enter project name and location. Cpck Finish > button. We have chosen name as EjbTester.

Right cpck on project name in Project explorer window. Select properties.

Add EJB component project created earper under pbraries using Add Project button in compile tab.

Add jboss pbraries using Add jar/folder button in compile tab. Jboss pbraries can be located at <jboss installation folder>> cpent folder.

Create jndi.properties under project say EjbTester.

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

Create package com.tutorialspoint.test and EJBTester.java class under it.

EJBTester.java

package com.tutorialspoint.test;
 
import com.tutorialspoint.stateless.LibrarySessionBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;
 
 
pubpc class EJBTester {
   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   pubpc static void main(String[] args) {
 
      EJBTester ejbTester = new EJBTester();
 
      ejbTester.testStatelessEjb();
   }
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   private void testStatelessEjb() {
      try {
         int choice = 1; 
         LibrarySessionBeanRemote pbraryBean = 
         (LibrarySessionBeanRemote)ctx.lookup("LibrarySessionBean/remote");
         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();                    
               pbraryBean.addBook(bookName);          
            }else if (choice == 2) {
               break;
            }
         }
         List<String> booksList = pbraryBean.getBooks();
         System.out.println("Book(s) entered so far: " + booksList.size());
         for (int i = 0; i < booksList.size(); ++i) {
            System.out.println((i+1)+". " + booksList.get(i));
         }
         LibrarySessionBeanRemote pbraryBean1 = 
         (LibrarySessionBeanRemote)ctx.lookup("LibrarySessionBean/remote");
         List<String> booksList1 = pbraryBean1.getBooks();
         System.out.println(
            "***Using second lookup to get pbrary stateless object***");
         System.out.println(
            "Book(s) entered so far: " + booksList1.size());
         for (int i = 0; i < booksList1.size(); ++i) {
            System.out.println((i+1)+". " + booksList1.get(i));
         }
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      } finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }  
}

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
***Using second lookup to get pbrary stateless object***
Book(s) entered so far: 0
BUILD SUCCESSFUL (total time: 13 seconds)

In the following chapters, we will cover multiple aspects of this complete EJB apppcation.

EJB - Stateless Bean

A stateless session bean is a type of enterprise bean, which is normally used to perform independent operations. A stateless session bean as per its name does not have any associated cpent state, but it may preserve its instance state. EJB Container normally creates a pool of few stateless bean s objects and use these objects to process cpent s request. Because of pool, instance variable values are not guaranteed to be same across lookups/method calls.

Steps to Create a Stateless EJB

Following are the steps required to create a stateless EJB −

Create a remote/local interface exposing the business methods.

This interface will be used by the EJB cpent apppcation.

Use @Local annotation, if EJB cpent is in same environment where EJB session bean is to be deployed.

Use @Remote annotation, if EJB cpent is in different environment where EJB session bean is to be deployed.

Create a stateless session bean, implementing the above interface.

Use @Stateless annotation to signify it a stateless bean. EJB Container automatically creates the relevant configurations or interfaces required by reading this annotation during deployment.

Remote Interface

import javax.ejb.Remote;
 
@Remote
pubpc interface LibrarySessionBeanRemote {
   //add business method declarations
}

Stateless EJB

@Stateless
pubpc class LibrarySessionBean implements LibrarySessionBeanRemote {
   //implement business method 
}

Example Apppcation

Let us create a test EJB apppcation to test stateless EJB.

EJBComponent (EJB Module)

LibrarySessionBeanRemote.java

package com.tutorialspoint.stateless;
 
import java.util.List;
import javax.ejb.Remote;
 
@Remote
pubpc interface LibrarySessionBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibrarySessionBean.java

 
package com.tutorialspoint.stateless;
 
import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateless;
 
@Stateless
pubpc class LibrarySessionBean implements LibrarySessionBeanRemote {
    
   List<String> bookShelf;    
 
   pubpc LibrarySessionBean() {
      bookShelf = new ArrayList<String>();
   }
 
   pubpc void addBook(String bookName) {
      bookShelf.add(bookName);
   }    
 
   pubpc List<String> getBooks() {
      return bookShelf;
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean - LibrarySessionBean/remote.

We will be using this lookup string to get remote business object of type - com.tutorialspoint.stateless.LibrarySessionBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibrarySessionBean/remote - EJB3.x Default Remote Business Interface
   LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibrarySessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBeanRemote ejbName: LibrarySessionBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
 
   LibrarySessionBean/remote - EJB3.x Default Remote Business Interface
   LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibrarySessionBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;
 
pubpc class EJBTester {
 
   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {
 
      EJBTester ejbTester = new EJBTester();
 
      ejbTester.testStatelessEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testStatelessEjb() {
 
      try {
         int choice = 1; 
 
         LibrarySessionBeanRemote pbraryBean =
         LibrarySessionBeanRemote)ctx.lookup("LibrarySessionBean/remote");
 
         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }
 
         List<Book> booksList = pbraryBean.getBooks();
 
         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }       
         LibrarySessionBeanRemote pbraryBean1 = 
            (LibrarySessionBeanRemote)ctx.lookup("LibrarySessionBean/remote");
         List<String> booksList1 = pbraryBean1.getBooks();
         System.out.println(
            "***Using second lookup to get pbrary stateless object***");
         System.out.println(
            "Book(s) entered so far: " + booksList1.size());
         for (int i = 0; i < booksList1.size(); ++i) {
            System.out.println((i+1)+". " + booksList1.get(i));
         }		 
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatelessEjb() method, jndi lookup is done with name - "LibrarySessionBean/remote" to obtain the remote business object (stateless ejb).

Then user is shown a pbrary store User Interface and he/she is asked to enter choice.

If user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in its instance variable.

If user enters 2, system retrieves books using stateless session bean getBooks() method and exits.

Then another jndi lookup is done with the name - "LibrarySessionBean/remote" to obtain the remote business object (stateless EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
***Using second lookup to get pbrary stateless object***
Book(s) entered so far: 0
BUILD SUCCESSFUL (total time: 13 seconds)

Run Cpent Again to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 0
***Using second lookup to get pbrary stateless object***
Book(s) entered so far: 1
1. Learn Java
BUILD SUCCESSFUL (total time: 12 seconds)

Output shown above may vary, depending upon how many stateless EJB object JBoss is maintaining.

In case, a single stateless EJB object is maintained, you may see the same pst of books after each lookup.

EJB Container may return the same stateless EJB object for every lookup.

Stateless EJB bean is keeping value of instance variable till the server is not restarted.

EJB - Stateful Bean

A stateful session bean is a type of enterprise bean, which preserve the conversational state with cpent. A stateful session bean as per its name keeps associated cpent state in its instance variables. EJB Container creates a separate stateful session bean to process cpent s each request. As soon as request scope is over, statelful session bean is destroyed.

Steps to Create Stateful EJB

Following are the steps required to create a stateful EJB −

Create a remote/local interface exposing the business methods.

This interface will be used by the EJB cpent apppcation.

Use @Local annotation if EJB cpent is in same environment where EJB session bean need to be deployed.

Use @Remote annotation if EJB cpent is in different environment where EJB session bean need to be deployed.

Create a stateful session bean, implementing the above interface.

Use @Stateful annotation to signify it a stateful bean. EJB Container automatically creates the relevant configurations or interfaces required by reading this annotation during deployment.

Remote Interface

import javax.ejb.Remote;
 
@Remote
pubpc interface LibraryStatefulSessionBeanRemote {
   //add business method declarations
}

Stateful EJB

@Stateful
pubpc class LibraryStatefulSessionBean implements LibraryStatefulSessionBeanRemote {
   //implement business method 
}

Example Apppcation

Let us create a test EJB apppcation to test stateful EJB.

EJBComponent (EJB Module)

LibraryStatefulSessionBeanRemote.java

package com.tutorialspoint.stateful;
 
import java.util.List;
import javax.ejb.Remote;
 
@Remote
pubpc interface LibraryStatefulSessionBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibraryStatefulSessionBean.java

package com.tutorialspoint.stateful;
 
import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateful;
 
@Stateful
pubpc class LibraryStatefulSessionBean implements LibraryStatefulSessionBeanRemote {
    
   List<String> bookShelf;    
 
   pubpc LibraryStatefulSessionBean() {
      bookShelf = new ArrayList<String>();
   }
 
   pubpc void addBook(String bookName) {
      bookShelf.add(bookName);
   }    
 
   pubpc List<String> getBooks() {
      return bookShelf;
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − LibraryStatefulSessionBean/remote.

We will be using this lookup string to get remote business object of type − com.tutorialspoint.stateful.LibraryStatefulSessionBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryStatefulSessionBean/remote - EJB3.x Default Remote Business Interface
   LibraryStatefulSessionBean/remote-com.tutorialspoint.stateful.LibraryStatefulSessionBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryStatefulSessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateful.LibraryStatefulSessionBeanRemote ejbName: LibraryStatefulSessionBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
 
   LibraryStatefulSessionBean/remote - EJB3.x Default Remote Business Interface
   LibraryStatefulSessionBean/remote-com.tutorialspoint.stateful.LibraryStatefulSessionBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial = org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs = org.jboss.naming:org.jnp.interfaces
java.naming.provider.url = localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateful session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryStatefulSessionBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;
 
pubpc class EJBTester {
 
   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {
 
      EJBTester ejbTester = new EJBTester();
 
      ejbTester.testStatelessEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testStatelessEjb() {
 
      try {
         int choice = 1; 
 
         LibraryStatefulSessionBeanRemote pbraryBean =
         LibraryStatefulSessionBeanRemote)ctx.lookup("LibraryStatefulSessionBean/remote");
 
         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }
 
         List<Book> booksList = pbraryBean.getBooks();
 
         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }       
         LibraryStatefulSessionBeanRemote pbraryBean1 = 
            (LibraryStatefulSessionBeanRemote)ctx.lookup("LibraryStatefulSessionBean/remote");
         List<String> booksList1 = pbraryBean1.getBooks();
         System.out.println(
            "***Using second lookup to get pbrary stateful object***");
         System.out.println(
            "Book(s) entered so far: " + booksList1.size());
         for (int i = 0; i < booksList1.size(); ++i) {
            System.out.println((i+1)+". " + booksList1.get(i));
         }		 
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with name - "LibraryStatefulSessionBean/remote" to obtain the remote business object (stateful ejb).

Then the user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If user enters 1, system asks for book name and saves the book using stateful session bean addBook() method. Session Bean is storing the book in its instance variable.

If user enters 2, system retrieves books using stateful session bean getBooks() method and exits.

Then another jndi lookup is done with the name - "LibraryStatefulSessionBean/remote" to obtain the remote business object (stateful EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console −

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
***Using second lookup to get pbrary stateful object***
Book(s) entered so far: 0
BUILD SUCCESSFUL (total time: 13 seconds)

Run Cpent Again to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 0
***Using second lookup to get pbrary stateful object***
Book(s) entered so far: 0
BUILD SUCCESSFUL (total time: 12 seconds)

Output shown above states that for each lookup, a different stateful EJB instance is returned.

Stateful EJB object is keeping value for single session only. As in second run, we are not getting any value of books.

EJB - Persistence

EJB 3.0, entity bean used in EJB 2.0 is largely replaced by persistence mechanism. Now entity bean is a simple POJO having mapping with table.

Following are the key actors in persistence API −

Entity − A persistent object representing the data-store record. It is good to be seriapzable.

EntityManager − Persistence interface to do data operations pke add/delete/update/find on persistent object(entity). It also helps to execute queries using Query interface.

Persistence unit (persistence.xml) − Persistence unit describes the properties of persistence mechanism.

Data Source (*ds.xml) − Data Source describes the data-store related properties pke connection url. user-name,password etc.

To demonstrate EJB persistence mechanism, we need to do the following tasks −

Step 1 − Create table in database.

Step 2 − Create Entity class corresponding to table.

Step 3 − Create Data Source and Persistence Unit.

Step 4 − Create a stateless EJB having EntityManager instance.

Step 5 − Update stateless EJB. Add methods to add records and get records from database via entity manager.

Step 6 − A console based apppcation cpent will access the stateless EJB to persist data in database.

Create Table

Create a table books in default database postgres.

CREATE TABLE books (
   id     integer PRIMARY KEY,
   name   varchar(50)
);

Create Entity class

//mark it entity using Entity annotation 
//map table name using Table annotation
@Entity
@Table(name="books")
pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }

   //mark id as primary key with autogenerated value
   //map database column id with id field
   @Id
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="id")
   pubpc int getId() {
      return id;
   }
   ...
}

Create DataSource and Persistence Unit

DataSource (jboss-ds.xml)

<?xml version = "1.0" encoding = "UTF-8"?>
<datasources>
   <local-tx-datasource>
      <jndi-name>PostgresDS</jndi-name>
      <connection-url>jdbc:postgresql://localhost:5432/postgres</connection-url>
      <driver-class>org.postgresql.driver</driver-class>
      <user-name>sa</user-name>
      <password>sa</password>
      <min-pool-size>5</min-pool-size>
      <max-pool-size>20</max-pool-size>
      <idle-timeout-minutes>5</idle-timeout-minutes>
   </local-tx-datasource>
</datasources>

Persistence Unit (persistence.xml)

<persistence version = "1.0" xmlns = "http://java.sun.com/xml/ns/persistence" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">

   <persistence-unit name = "EjbComponentPU" transaction-type = "JTA">
      <jta-data-source>java:/PostgresDS</jta-data-source>
      <exclude-unpsted-classes>false</exclude-unpsted-classes>
      <properties/>
   </persistence-unit>
   
   <persistence-unit name = "EjbComponentPU2" transaction-type = "JTA">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
      <jta-data-source>java:/PostgresDS</jta-data-source>
      <exclude-unpsted-classes>false</exclude-unpsted-classes>
	  
      <properties>
         <property name="hibernate.hbm2ddl.auto" value="update"/>
      </properties>
   </persistence-unit>
   
</persistence>

Create Stateless EJB Having EntityManager Instance

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   //pass persistence unit to entityManager.
   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {        
      return entityManager.createQuery("From Books").getResultList();
   }
   ...
}

After building the EJB module, we need a cpent to access the stateless bean, which we will be going to create in the next section.

Example Apppcation

Let us create a test EJB apppcation to test EJB persistence mechanism.

EJBComponent (EJB Module)

Book.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="books")
pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }

   @Id
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="id")
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }    
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {
      return entityManager.createQuery("From Book").getResultList();
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean - LibraryPersistentBean/remote.

We will be using this lookup string to get remote business object of type - com.tutorialspoint.stateless.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBeanRemote,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEntityEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEntityEjb() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean =
         LibraryPersistentBeanRemote)ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks.

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with name - "LibraryStatefulSessionBean/remote" to obtain the remote business object (stateful ejb).

Then user is shown a pbrary store User Interface and he/she is asked to enter choice.

If user enters 1, system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is persisting the book in database via EntityManager call.

If user enters 2, system retrieves books using stateful session bean getBooks() method and exits.

Then another jndi lookup is done with name - "LibraryStatelessSessionBean/remote" to obtain the remote business object (stateless EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console −

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn java
BUILD SUCCESSFUL (total time: 15 seconds)

Run Cpent Again to Access EJB

Restart the JBoss before accessing the EJB.

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Spring
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 2
1. learn java
2. Learn Spring
BUILD SUCCESSFUL (total time: 15 seconds)

The output shown above states that books are getting stored in persistent storage and are retrieved from database.

EJB - Message Driven Beans

A message driven bean is a type of enterprise bean, which is invoked by EJB container when it receives a message from queue or topic. Message driven bean is a stateless bean and is used to do task asynchronously.

To demonstrate use of message driven bean, we will make use of EJB-persistence chapter and we need to do the following tasks −

Step 1 − Create table in database (Refer to EJB-Persistence chapter).

Step 2 − Create Entity class corresponding to table (Refer to EJB-Persistence chapter).

Step 3 − Create DataSource and Persistence Unit (Refer to EJB-Persistence chapter).

Step 4 − Create a stateless EJB having EntityManager instance (Refer to EJB-Persistence chapter).

Step 5 − Update stateless ejb.Add methods to add records and get records from database via entity manager (Refer to EJB-Persistence chapter).

Step 6 − Create a Queue named BookQueue in JBoss default apppcation directory.

Step 7 − A console based apppcation cpent will send message to this queue.

Step 8 − Create a Message driven bean, which will use the stateless bean to persist the cpent data.

Step 9 − EJB Container of jboss will call the above message driven bean and pass it the message that cpent will be sending to.

Create Queue

Create a file named jbossmq-destinations-service.xml if not exists in <JBoss Installation Folder> > server > default > deploy folder.

Here we are creating a queue named BookQueue −

jbossmq-destinations-service.xml

<mbean code="org.jboss.mq.server.jmx.Queue"  
   name="jboss.mq.destination:service=Queue,name=BookQueue">  
   <depends optional-attribute-name="DestinationManager">
      jboss.mq:service=DestinationManager
   </depends>  
</mbean>  

When you start the JBoss, you will see a similar entry in jboss log.

...
10:37:06,167 INFO  [QueueService] Queue[/queue/BookQueue] started, fullSize=200000, pageSize=2000, downCacheSize=2000
...

Create Message Driven Bean

@MessageDriven(
   name = "BookMessageHandler",
   activationConfig = {
      @ActivationConfigProperty( propertyName = "destinationType", 
                                 propertyValue = "javax.jms.Queue"),
      @ActivationConfigProperty( propertyName = "destination", 
                                 propertyValue ="/queue/BookQueue")
   }
)
pubpc class LibraryMessageBean implements MessageListener {
 
   @Resource
   private MessageDrivenContext mdctx;  
 
   @EJB
   LibraryPersistentBeanRemote pbraryBean;
 
   pubpc LibraryMessageBean() {        
   }
 
   pubpc void onMessage(Message message) {
   }
}

LibraryMessageBean is annotated with @MessageDriven annotation to mark it as message driven bean.

Its properties are defined as destinationType - Queue and destination - /queue/BookQueue.

It implements MessageListener interface, which exposes onMessage method.

It has MessgeDrivenContext as a resource.

LibraryPersistentBeanRemote stateless bean is injected in this bean for persistence purpose.

Build the EjbComponent project and deploy it on JBoss. After building and deploying the EJB module, we need a cpent to send a message to jboss queue.

Example Apppcation

Let us create a test EJB apppcation to test Message Driven Bean.

EJBComponent (EJB Module)

LibraryMessageBean.java

package com.tutorialspoint.messagebean;
 
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import javax.annotation.Resource;
import javax.ejb.ActivationConfigProperty;
import javax.ejb.EJB;
import javax.ejb.MessageDriven;
import javax.ejb.MessageDrivenContext;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.ObjectMessage;
 
@MessageDriven(
   name = "BookMessageHandler",
   activationConfig = {
      @ActivationConfigProperty( propertyName = "destinationType", 
                                 propertyValue = "javax.jms.Queue"),
      @ActivationConfigProperty( propertyName = "destination", 
                                 propertyValue ="/queue/BookQueue")
   }
)
pubpc class LibraryMessageBean implements MessageListener {
 
   @Resource
   private MessageDrivenContext mdctx;  
 
   @EJB
   LibraryPersistentBeanRemote pbraryBean;
 
   pubpc LibraryMessageBean() {        
   }
 
   pubpc void onMessage(Message message) {
      ObjectMessage objectMessage = null;
      try {
         objectMessage = (ObjectMessage) message;
         Book book = (Book) objectMessage.getObject(); 
         pbraryBean.addBook(book);
 
      } catch (JMSException ex) {
         mdctx.setRollbackOnly();
      }       
   }   
}

EJBTester (EJB Cpent)

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.jms.ObjectMessage;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.naming.InitialContext;
import javax.naming.NamingException;
 
pubpc class EJBTester {
 
   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {
 
      EJBTester ejbTester = new EJBTester();
 
      ejbTester.testMessageBeanEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testMessageBeanEjb() {
 
      try {
         int choice = 1; 
         Queue queue = (Queue) ctx.lookup("/queue/BookQueue");
         QueueConnectionFactory factory =
         (QueueConnectionFactory) ctx.lookup("ConnectionFactory");
         QueueConnection connection =  factory.createQueueConnection();
         QueueSession session = 
         connection.createQueueSession(false, QueueSession.AUTO_ACKNOWLEDGE);
         QueueSender sender = session.createSender(queue);
 
         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               ObjectMessage objectMessage = 
                  session.createObjectMessage(book);
               sender.send(objectMessage); 
            } else if (choice == 2) {
               break;
            }
         }
 
         LibraryPersistentBeanRemote pbraryBean = 
         (LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");
 
         List<Book> booksList = pbraryBean.getBooks();
 
         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }   
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with the name - "/queue/BookQueue" to obtain treference of queue available in Jboss. Then sender is created using queue session.

Then user is shown a pbrary store User Interface and he/she is asked to enter choice.

If user enters 1, the system asks for book name and sender sends the book name to queue. When JBoss container receives this message in queue, it calls our message driven bean s onMessage method. Our message driven bean then saves book using stateful session bean addBook() method. Session Bean is persisting the book in database via EntityManager call.

If user enters 2, then another jndi lookup is done with name - "LibraryStatefulSessionBean/remote" to obtain the remote business object (stateful EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console −

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn EJB
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 2
1. learn java
1. learn EJB
BUILD SUCCESSFUL (total time: 15 seconds)

The output shown above states that our Message driven bean is receiving the message and storing the book in persistent storage and books are retrieved from the database.

EJB - Annotations

Annotations were introduced in Java 5.0. The purpose of having annotations is to attach additional information in the class or a meta-data of a class within its source code. In EJB 3.0, annotations are used to describe configuration meta-data in EJB classes. By this way, EJB 3.0 epminates the need to describe configuration data in configuration XML files.

EJB container uses compiler tool to generate required artifacts pke interfaces, deployment descriptors by reading those annotations. Following is the pst of commonly used annotations.

EJB - Callbacks

Callback is a mechanism by which the pfe cycle of an enterprise bean can be intercepted. EJB 3.0 specification has specified callbacks for which callback handler methods are created. EJB Container calls these callbacks. We can define callback methods in the EJB class itself or in a separate class. EJB 3.0 has provided many annotations for callbacks.

Following is the pst of callback annotations for stateless bean −

Following is the pst of callback annotations for stateful bean −

Following is the pst of callback annotations for message driven bean −

Following is the pst of callback annotations for entity bean −

Example Apppcation

Let us create a test EJB apppcation to test various callbacks in EJB.

EJBComponent (EJB Module)

BookCallbackListener.java

package com.tutorialspoint.callback;

import javax.persistence.PrePersist;
import javax.persistence.PostLoad;
import javax.persistence.PostPersist;
import javax.persistence.PostRemove;
import javax.persistence.PostUpdate;
import javax.persistence.PreRemove;
import javax.persistence.PreUpdate;

import com.tutorialspoint.entity.Book;

pubpc class BookCallbackListener {
    
   @PrePersist
   pubpc void prePersist(Book book) {
      System.out.println("BookCallbackListener.prePersist:" 
         + "Book to be created with book id: "+book.getId());
   }

   @PostPersist
   pubpc void postPersist(Object book) {
      System.out.println("BookCallbackListener.postPersist::"
         + "Book created with book id: "+((Book)book).getId());
   }

   @PreRemove
   pubpc void preRemove(Book book) {
      System.out.println("BookCallbackListener.preRemove:"
         + " About to delete Book: " + book.getId());
   }

   @PostRemove
   pubpc void postRemove(Book book) {
      System.out.println("BookCallbackListener.postRemove::"
         + " Deleted Book: " + book.getId());
   }

   @PreUpdate
   pubpc void preUpdate(Book book) {
      System.out.println("BookCallbackListener.preUpdate::"
         + " About to update Book: " + book.getId());
   }

   @PostUpdate
   pubpc void postUpdate(Book book) {
      System.out.println("BookCallbackListener.postUpdate::"
         + " Updated Book: " + book.getId());
   }

   @PostLoad
   pubpc void postLoad(Book book) {
      System.out.println("BookCallbackListener.postLoad::"
         + " Loaded Book: " + book.getId());
   }
}

Book.java

package com.tutorialspoint.entity;
 
import java.io.Seriapzable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
 
@Entity
@Table(name="books")
pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;
 
   pubpc Book() {        
   }
 
   @Id
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="id")
   pubpc int getId() {
      return id;
   }
 
   pubpc void setId(int id) {
      this.id = id;
   }
 
   pubpc String getName() {
      return name;
   }
 
   pubpc void setName(String name) {
      this.name = name;
   }    
}

LibraryStatefulSessionBean.java

package com.tutorialspoint.stateful;

import java.util.ArrayList;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

import javax.ejb.PostActivate;
import javax.ejb.PrePassivate;
import javax.ejb.Stateful;

@Stateful
pubpc class LibraryStatefulSessionBean 
   implements LibraryStatefulSessionBeanRemote {
   List<String> bookShelf;    

   pubpc LibraryStatefulSessionBean() {
      bookShelf = new ArrayList<String>();
   }

   pubpc void addBook(String bookName) {
      bookShelf.add(bookName);
   }    

   pubpc List<String> getBooks() {
      return bookShelf;
   }

   @PostConstruct
   pubpc void postConstruct() {
      System.out.println("LibraryStatefulSessionBean.postConstruct::"
         + " bean created.");
   }

   @PreDestroy
   pubpc void preDestroy() {
      System.out.println("LibraryStatefulSessionBean.preDestroy:"
         + " bean removed.");
   }

   @PostActivate
   pubpc void postActivate() {
      System.out.println("LibraryStatefulSessionBean.postActivate:"
         + " bean activated.");
   }

   @PrePassivate
   pubpc void prePassivate() {
      System.out.println("LibraryStatefulSessionBean.prePassivate:"
         + " bean passivated.");
   }    
}

LibraryStatefulSessionBeanRemote.java

package com.tutorialspoint.stateful;

import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryStatefulSessionBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
pubpc class LibraryPersistentBean 
   implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {}

   @PersistenceContext(unitName="EntityEjbPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {     
      return entityManager.createQuery("From Book")
         .getResultList();
   }

   @PostConstruct
   pubpc void postConstruct() {
      System.out.println("postConstruct:: LibraryPersistentBean session bean"
         + " created with entity Manager object: ");
   }

   @PreDestroy
   pubpc void preDestroy() {
      System.out.println("preDestroy: LibraryPersistentBean session"
      + " bean is removed ");
   }
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean - LibraryPersistentBean/remote.

We will be using this lookup string to get remote business object of type - com.tutorialspoint.stateless.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBeanRemote ejbName: LibraryPersistentBean
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibrarySessionBeanRemote;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.List;
import java.util.Properties;

import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEntityEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEntityEjb() {    
      try {
      int choice = 1; 

      LibraryPersistentBeanRemote pbraryBean = 
      (LibraryPersistentBeanRemote)
      ctx.lookup("LibraryPersistentBean/remote");

      while (choice != 2) {
         String bookName;
         showGUI();
         String strChoice = brConsoleReader.readLine();
         choice = Integer.parseInt(strChoice);
         if (choice == 1) {
            System.out.print("Enter book name: ");
            bookName = brConsoleReader.readLine();
            Book book = new Book();
            book.setName(bookName);
            pbraryBean.addBook(book);          
         } else if (choice == 2) {
            break;
         }
      }

      List<Book> booksList = pbraryBean.getBooks();

      System.out.println("Book(s) entered so far: " + booksList.size());
      int i = 0;
      for (Book book:booksList) {
         System.out.println((i+1)+". " + book.getName());
         i++;
      }           

      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }    
   }    
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatelessEjb() method, jndi lookup is done with the name - "LibrarySessionBean/remote" to obtain the remote business object (stateless EJB).

Then user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in the database.

If user enters 2, system retrieves books using stateless session bean getBooks() method and exits.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
BUILD SUCCESSFUL (total time: 13 seconds)

JBoss Apppcation Server Log Output

You can find the following callback entries in JBoss log

14:08:34,293 INFO  [STDOUT] postConstruct:: LibraryPersistentBean session bean created with entity Manager object
...
16:39:09,484 INFO  [STDOUT] BookCallbackListener.prePersist:: Book to be created with book id: 0
16:39:09,531 INFO  [STDOUT] BookCallbackListener.postPersist:: Book created with book id: 1
16:39:09,900 INFO  [STDOUT] BookCallbackListener.postLoad:: Loaded Book: 1
...

EJB - Timer Service

Timer Service is a mechanism by which scheduled apppcation can be build. For example, salary spp generation on the 1st of every month. EJB 3.0 specification has specified @Timeout annotation, which helps in programming the EJB service in a stateless or message driven bean. EJB Container calls the method, which is annotated by @Timeout.

EJB Timer Service is a service provided by EJB container, which helps to create timer and to schedule callback when timer expires.

Steps to Create Timer

Inject SessionContext in bean using @Resource annotation −

@Stateless
pubpc class TimerSessionBean {

   @Resource
   private SessionContext context;
   ...
}

Use SessionContext object to get TimerService and to create timer. Pass time in milpseconds and message.

pubpc void createTimer(long duration) {
   context.getTimerService().createTimer(duration, "Hello World!");
}

Steps to Use Timer

Use @Timeout annotation to a method. Return type should be void and pass a parameter of type Timer. We are cancepng the timer after first execution otherwise it will keep running after fix intervals.

@Timeout
pubpc void timeOutHandler(Timer timer) {
   System.out.println("timeoutHandler : " + timer.getInfo());        
   timer.cancel();
}

Example Apppcation

Let us create a test EJB apppcation to test Timer Service in EJB.

EJBComponent (EJB Module)

TimerSessionBean.java

package com.tutorialspoint.timer;

import javax.annotation.Resource;
import javax.ejb.SessionContext;
import javax.ejb.Timer;
import javax.ejb.Stateless;
import javax.ejb.Timeout;

@Stateless
pubpc class TimerSessionBean implements TimerSessionBeanRemote {

   @Resource
   private SessionContext context;

   pubpc void createTimer(long duration) {
      context.getTimerService().createTimer(duration, "Hello World!");
   }

   @Timeout
   pubpc void timeOutHandler(Timer timer) {
      System.out.println("timeoutHandler : " + timer.getInfo());        
      timer.cancel();
   }
}

TimerSessionBeanRemote.java

package com.tutorialspoint.timer;

import javax.ejb.Remote;

@Remote
pubpc interface TimerSessionBeanRemote {
   pubpc void createTimer(long milpseconds);
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − TimerSessionBean/remote.

We will using this lookup string to get remote business object of type − com.tutorialspoint.timer.TimerSessionBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   TimerSessionBean/remote - EJB3.x Default Remote Business Interface
   TimerSessionBean/remote-com.tutorialspoint.timer.TimerSessionBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=TimerSessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.timer.TimerSessionBeanRemote ejbName: TimerSessionBean
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.TimerSessionBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testTimerService();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testTimerService() {
      try {
         TimerSessionBeanRemote timerServiceBean = (TimerSessionBeanRemote)ctx.lookup("TimerSessionBean/remote");

         System.out.println("["+(new Date()).toString()+ "]" + "timer created.");
         timerServiceBean.createTimer(2000);            

      } catch (NamingException ex) {
         ex.printStackTrace();
      }
   }
}

EJBTester is doing the following tasks.

Load properties from jndi.properties and initiapze the InitialContext object.

In testTimerService() method, jndi lookup is done with the name - "TimerSessionBean/remote" to obtain the remote business object (timer stateless EJB).

Then createTimer is invoked passing 2000 milpseconds as schedule time.

EJB Container calls the timeoutHandler method after 2 seconds.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
[Wed Jun 19 11:35:47 IST 2013]timer created.
BUILD SUCCESSFUL (total time: 0 seconds)

JBoss Apppcation Server Log Output

You can find the following callback entries in JBoss log

...
11:35:49,555 INFO  [STDOUT] timeoutHandler : Hello World!
...

EJB - Dependency Injection

EJB 3.0 specification provides annotations, which can be appped on fields or setter methods to inject dependencies. EJB Container uses the global JNDI registry to locate the dependency. Following annotations are used in EJB 3.0 for dependency injection.

@EJB − used to inject other EJB reference.

@Resource − used to inject datasource or singleton services pke sessionContext, timerService etc.

Steps to Use @EJB

@EJB can be used on fields or on methods in the following manner −

pubpc class LibraryMessageBean implements MessageListener {
   //dependency injection on field. 
   @EJB
   LibraryPersistentBeanRemote pbraryBean;
   ...
}
pubpc class LibraryMessageBean implements MessageListener {
  
   LibraryPersistentBeanRemote pbraryBean;
   
   //dependency injection on method. 
   @EJB(beanName="com.tutorialspoint.stateless.LibraryPersistentBean")
   pubpc void setLibraryPersistentBean(
   LibraryPersistentBeanRemote pbraryBean)
   {
      this.pbraryBean = pbraryBean;
   }
   ...
}

Steps to use @Resource

@Resource is normally used to inject EJB Container provided singletons.

pubpc class LibraryMessageBean implements MessageListener {
   @Resource
   private MessageDrivenContext mdctx;  
   ...
}

Example Apppcation

Let us create a test EJB apppcation to test Dependency Injection Service in EJB.

EJBComponent (EJB Module)

LibraryMessageBean.java

package com.tuturialspoint.messagebean;
 
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import javax.annotation.Resource;
import javax.ejb.ActivationConfigProperty;
import javax.ejb.EJB;
import javax.ejb.MessageDriven;
import javax.ejb.MessageDrivenContext;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.ObjectMessage;
 
@MessageDriven(
   name = "BookMessageHandler",
   activationConfig = {
      @ActivationConfigProperty( propertyName = "destinationType", 
                                 propertyValue = "javax.jms.Queue"),
      @ActivationConfigProperty( propertyName = "destination", 
                                 propertyValue ="/queue/BookQueue")
   }
)
pubpc class LibraryMessageBean implements MessageListener {
 
   @Resource
   private MessageDrivenContext mdctx;  
 
   @EJB
   LibraryPersistentBeanRemote pbraryBean;
 
   pubpc LibraryMessageBean() {        
   }
 
   pubpc void onMessage(Message message) {
      ObjectMessage objectMessage = null;
      try {
         objectMessage = (ObjectMessage) message;
         Book book = (Book) objectMessage.getObject(); 
         pbraryBean.addBook(book);
 
      }catch (JMSException ex) {
         mdctx.setRollbackOnly();
      }       
   }   
}

EJBTester (EJB Cpent)

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.jms.ObjectMessage;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.naming.InitialContext;
import javax.naming.NamingException;
 
pubpc class EJBTester {
 
   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {
 
      EJBTester ejbTester = new EJBTester();
 
      ejbTester.testMessageBeanEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testMessageBeanEjb() {
 
      try {
         int choice = 1; 
         Queue queue = (Queue) ctx.lookup("/queue/BookQueue");
         QueueConnectionFactory factory =
         (QueueConnectionFactory) ctx.lookup("ConnectionFactory");
         QueueConnection connection =  factory.createQueueConnection();
         QueueSession session = connection.createQueueSession( 
         false, QueueSession.AUTO_ACKNOWLEDGE);
         QueueSender sender = session.createSender(queue);
 
         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               ObjectMessage objectMessage = 
               session.createObjectMessage(book);
               sender.send(objectMessage); 
            } else if (choice == 2) {
               break;
            }
         }
 
         LibraryPersistentBeanRemote pbraryBean = 
         (LibraryPersistentBeanRemote)
		 ctx.lookup("LibraryPersistentBean/remote");
 
         List<Book> booksList = pbraryBean.getBooks();
 
         System.out.println("Book(s) entered so far: " 
         + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }   
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with the name - "/queue/BookQueue" to obtain reference of queue available in Jboss. Then sender is created using queue session.

Then the user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and sender sends the book name to queue. When JBoss container receives this message in queue, it calls our message driven bean s onMessage method. Our message driven bean then saves book using stateful session bean addBook() method. Session Bean is persisting the book in database via EntityManager call.

If the user enters 2, then another jndi lookup is done with the name - "LibraryStatefulSessionBean/remote" to obtain the remote business object (stateful EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn EJB
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 2
1. learn java
1. learn EJB
BUILD SUCCESSFUL (total time: 15 seconds)

The output shown above states that our Message driven bean is receiving the message and storing book in persistent storage and books are retrieved from database.

Our message driven bean is using LibraryPersistentBean injected into it using @EJB annotation and in case of exception, MessageDrivenContext, object is used to rollback the transaction.

EJB - Interceptors

EJB 3.0 provides specification to intercept business methods calls using methods annotated with @AroundInvoke annotation. An interceptor method is called by ejbContainer before business method call it is intercepting. Following is the example signature of an interceptor method

@AroundInvoke
pubpc Object methodInterceptor(InvocationContext ctx) throws Exception {
   System.out.println("*** Intercepting call to LibraryBean method: " 
   + ctx.getMethod().getName());
   return ctx.proceed();
}

Interceptor methods can be appped or bound at three levels.

Default − Default interceptor is invoked for every bean within deployment.Default interceptor can be appped only via xml (ejb-jar.xml).

Class − Class level interceptor is invoked for every method of the bean. Class level interceptor can be appped both by annotation of via xml(ejb-jar.xml).

Method− Method level interceptor is invoked for a particular method of the bean. Method level interceptor can be appped both by annotation of via xml(ejb-jar.xml).

We are discussing Class level interceptor here.

Interceptor Class

package com.tutorialspoint.interceptor;

import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;

pubpc class BusinessInterceptor {
   @AroundInvoke
   pubpc Object methodInterceptor(InvocationContext ctx) throws Exception {
      System.out.println("*** Intercepting call to LibraryBean method: " 
      + ctx.getMethod().getName());
      return ctx.proceed();
   }
}

Remote Interface

import javax.ejb.Remote;

@Remote
pubpc interface LibraryBeanRemote {
   //add business method declarations
}

Intercepted Stateless EJB

@Interceptors ({BusinessInterceptor.class})
@Stateless
pubpc class LibraryBean implements LibraryBeanRemote {
   //implement business method 
}

Example Apppcation

Let us create a test EJB apppcation to test intercepted stateless EJB.

EJBComponent (EJB Module)

LibraryBeanRemote.java

package com.tutorialspoint.interceptor;

import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibraryBean.java

package com.tutorialspoint.interceptor;

import java.util.ArrayList;
import java.util.List;

import javax.ejb.Stateless;
import javax.interceptor.Interceptors;

@Interceptors ({BusinessInterceptor.class})
@Stateless
pubpc class LibraryBean implements LibraryBeanRemote {
    
   List<String> bookShelf;    

   pubpc LibraryBean() {
      bookShelf = new ArrayList<String>();
   }

   pubpc void addBook(String bookName) {
      bookShelf.add(bookName);
   }    

   pubpc List<String> getBooks() {
      return bookShelf;
   }   
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − LibraryBean/remote.

We will using this lookup string to get remote business object of type − com.tutorialspoint.interceptor.LibraryBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryBean/remote - EJB3.x Default Remote Business Interface
   LibraryBean/remote-com.tutorialspoint.interceptor.LibraryBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.interceptor.LibraryBeanRemote ejbName: LibraryBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryBean/remote - EJB3.x Default Remote Business Interface
   LibraryBean/remote-com.tutorialspoint.interceptor.LibraryBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.List;
import java.util.Properties;

import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testInterceptedEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testInterceptedEjb() {

      try {
         int choice = 1; 

         LibraryBeanRemote pbraryBean =
         LibraryBeanRemote)ctx.lookup("LibraryBean/remote");

         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }                
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testInterceptedEjb() method, jndi lookup is done with the name - "LibraryBean/remote" to obtain the remote business object (stateless EJB).

Then user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in its instance variable.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
BUILD SUCCESSFUL (total time: 13 seconds)

JBoss Apppcation Server Log Output

Verify the following output in JBoss Apppcation server log output.

....
09:55:40,741 INFO  [STDOUT] *** Intercepting call to LibraryBean method: addBook
09:55:43,661 INFO  [STDOUT] *** Intercepting call to LibraryBean method: getBooks

EJB - Embeddable Objects

EJB 3.0 provides option to embed JAVA POJO (Plain Old Java Object) into an entity bean and allows to map column names with the methods of the embedded POJO class. A java POJO to be embedded must be annotated as @Embeddable.

@Embeddable
pubpc class Pubpsher implements Seriapzable{
   private String name;
   private String address;
   ...
}

The above class can be embedded using @Embedded annotation.

@Entity
pubpc class Book implements Seriapzable{
   private int id;
   private String name;
   private Pubpsher pubpsher;
   ...
   @Embedded
   @AttributeOverrides({
      @AttributeOverride(name = "name", 
                      column = @Column(name = "PUBLISHER")),
      @AttributeOverride(name = "address", 
                      column = @Column(name = "PUBLISHER_ADDRESS"))
   })
   pubpc Pubpsher getPubpsher() {
      return pubpsher;
   }
   ...
}

Example Apppcation

Let us create a test EJB apppcation to test embedded objects in EJB 3.0.

Create/Alter Book Table

CREATE TABLE book (
   id     integer PRIMARY KEY,
   name   varchar(50)
);
Alter table book add pubpsher varchar(100);
Alter table book add pubpsher_address varchar(200);

EJBComponent (EJB Module)

Pubpsher.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;
import javax.persistence.Embeddable;

@Embeddable
pubpc class Pubpsher implements Seriapzable{
    
   private String name;
   private String address;

   pubpc Pubpsher() {}

   pubpc Pubpsher(String name, String address) {
      this.name = name;
      this.address = address;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }

   pubpc String getAddress() {
      return address;
   }

   pubpc void setAddress(String address) {
      this.address = address;
   }

   pubpc String toString() {
      return name + "," + address;
   }    
}

Book.java

package com.tutorialspoint.entity;

import com.tutorialspoint.callback.BookCallbackListener;
import java.io.Seriapzable;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="book")
pubpc class Book implements Seriapzable{

   private int id;
   private String name;
   private Pubpsher pubpsher;

   pubpc Book() {        
   }

   @Id
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="id")
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }


   @Embedded
   @AttributeOverrides({
      @AttributeOverride(name = "name", 
         column = @Column(name = "PUBLISHER")),
      @AttributeOverride(name = "address", 
         column = @Column(name = "PUBLISHER_ADDRESS"))
   })
   pubpc Pubpsher getPubpsher() {
      return pubpsher;
   }

   pubpc void setPubpsher(Pubpsher pubpsher) {
      this.pubpsher = pubpsher;
   }    
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {
      return entityManager.createQuery("From Book").getResultList();
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − LibraryPersistentBean/remote.

We will be using this lookup string to get remote business object of type − com.tutorialspoint.interceptor.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.interceptor.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.List;
import java.util.Properties;

import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEmbeddedObjects();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEmbeddedObjects() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean = 
        (LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            String pubpsherName;
            String pubpsherAddress;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               System.out.print("Enter pubpsher name: ");
               pubpsherName = brConsoleReader.readLine();
               System.out.print("Enter pubpsher address: ");
               pubpsherAddress = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               book.setPubpsher
              (new Pubpsher(pubpsherName,pubpsherAddress));

               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            System.out.println("Pubpcation: "+book.getPubpsher());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testInterceptedEjb() method, jndi lookup is done with the name - "LibraryPersistenceBean/remote" to obtain the remote business object (stateless EJB).

Then the user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1,the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in database.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: learn html5
Enter pubpsher name: SAMS
Enter pubpsher address: DELHI
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn html5
Pubpcation: SAMS,DELHI
BUILD SUCCESSFUL (total time: 21 seconds)

EJB - Blobs/Clobs

EJB 3.0 provides support for Blob and Clob types using @Lob annotation. Following java types can be mapped using @Lob annotation.

java.sql.Blob

java.sql.Clob

byte[]

String

Seriapzable Object

@Entity
@Table(name="books")
@EntityListeners(BookCallbackListener.class)
pubpc class Book implements Seriapzable{
   ...
   private byte[] image;    

   @Lob @Basic(fetch= FetchType.EAGER)
   pubpc byte[] getImage() {
      return image;
   }
   ...
}

Example Apppcation

Let us create a test EJB apppcation to test blob/clob support in EJB 3.0.

Create/Alter Book Table

CREATE TABLE book (
   id     integer PRIMARY KEY,
   name   varchar(50)
);
Alter table book add image bytea;
Alter table book add xml text;

EJBComponent (EJB Module)

Book.java

package com.tutorialspoint.entity;

import com.tutorialspoint.callback.BookCallbackListener;
import java.io.Seriapzable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;

@Entity
@Table(name="book")
pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;    
   private byte[] image;   
   private String xml;

   pubpc Book() {        
   }

   @Id
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="id")
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }

   @Lob @Basic(fetch= FetchType.EAGER)
   pubpc byte[] getImage() {
      return image;
   }

   pubpc void setImage(byte[] image) {
      this.image = image;
   }

   @Lob @Basic(fetch= FetchType.EAGER)
   pubpc String getXml() {
      return xml;
   }

   pubpc void setXml(String xml) {
      this.xml = xml;
   }
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {
      return entityManager.createQuery("From Book").getResultList();
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean - LibraryPersistentBean/remote.

We will using this lookup string to get remote business object of type - com.tutorialspoint.interceptor.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.interceptor.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testBlobClob();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testBlobClob() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean = 
        (LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            String pubpsherName;
            String pubpsherAddress;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               String xml = "<book><name>"+bookName+"</name></book>";
               Book book = new Book();
               book.setName(bookName);                                        
               byte[] imageBytes = {0x32, 0x32,0x32, 0x32,0x32,
               0x32,0x32, 0x32,
               0x32, 0x32,0x32, 0x32,0x32, 0x32,0x32, 0x32,
               0x32, 0x32,0x32, 0x32,0x32, 0x32,0x32, 0x32
               };
               book.setImage(imageBytes);
               book.setXml(xml);

               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            byte[] imageByts = book.getImage();
            if(imageByts != null) {
               System.out.print("image bytes: [");
               for(int j = 0; j < imageByts.length ; j++) {
                  System.out.print("0x" 
                  + String.format("%x", imageByts[j]) +" ");
               }            
               System.out.println("]");
            }        
            System.out.println(book.getXml());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks.

Load properties from jndi.properties and initiapze the InitialContext object.

In testInterceptedEjb() method, jndi lookup is done with name - "LibraryPersistenceBean/remote" to obtain the remote business object (stateless EJB).

Then the user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in database.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: learn testing
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn testing
image bytes: [
   0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 ]
<book><name>learn testing</name></book>
BUILD SUCCESSFUL (total time: 20 seconds)

EJB - Transactions

A transaction is a single unit of work items, which follows the ACID properties. ACID stands for Atomic, Consistent, Isolated, and Durable.

Atomic − If any of the work item fails, the whole unit will be considered failed. Success meant, all items execute successfully.

Consistent − A transaction must keep the system in consistent state.

Isolated − Each transaction executes independent of any other transaction.

Durable − Transaction should survive system failure if it has been executed or committed.

EJB Container/Servers are transaction servers and handles transactions context propagation and distributed transactions. Transactions can be managed by the container or by custom code handpng in bean s code.

Container Managed Transactions − In this type, the container manages the transaction states.

Bean Managed Transactions − In this type, the developer manages the pfe cycle of transaction states.

Container Managed Transactions

EJB 3.0 has specified following attributes of transactions, which EJB containers implement −

REQUIRED − Indicates that business method has to be executed within transaction, otherwise a new transaction will be started for that method.

REQUIRES_NEW − Indicates that a new transaction, is to be started for the business method.

SUPPORTS − Indicates that business method will execute as part of transaction.

NOT_SUPPORTED − Indicates that business method should not be executed as part of transaction.

MANDATORY − Indicates that business method will execute as part of transaction, otherwise exception will be thrown.

NEVER − Indicates if business method executes as part of transaction, then an exception will be thrown.

Example

package com.tutorialspoint.txn.required;
 
import javax.ejb.*
 
@Stateless
@TransactionManagement(TransactionManagementType.CONTAINER)
pubpc class UserDetailBean implements UserDetailRemote {
	
   private UserDetail;

   @TransactionAttribute(TransactionAttributeType.REQUIRED)
   pubpc void createUserDetail() {
      //create user details object
   }
}

createUserDetail() business method is made Required using Required annotation.

package com.tutorialspoint.txn.required;
 
import javax.ejb.*
 
@Stateless
pubpc class UserSessionBean implements UserRemote {
	
   private User;

   @EJB
   private UserDetailRemote userDetail;

   pubpc void createUser() {
      //create user 
      //...
      //create user details
      userDetail.createUserDetail();
   }
}

createUser() business method is using createUserDetail(). If exception occurred during createUser() call and User object is not created then UserDetail object will also not be created.

Bean Managed Transactions

In Bean Managed Transactions, Transactions can be managed by handpng exceptions at apppcation level.

Following are the key points to be considered −

Start − When to start a transaction in a business method.

Sucess − Identify success scenario when a transaction is to be committed.

Failed − Identify failure scenario when a transaction is to be rollback.

Example

package com.tutorialspoint.txn.bmt;
 
import javax.annotation.Resource;
import javax.ejb.Stateless;
import javax.ejb.TransactionManagement;
import javax.ejb.TransactionManagementType;
import javax.transaction.UserTransaction;
 
@Stateless
@TransactionManagement(value=TransactionManagementType.BEAN)
pubpc class AccountBean implements AccountBeanLocal {
 
   @Resource
   private UserTransaction userTransaction;

   pubpc void transferFund(Account fromAccount, double fund , 
      Account toAccount) throws Exception{

      try{
         userTransaction.begin();

         confirmAccountDetail(fromAccount);
         withdrawAmount(fromAccount,fund);

         confirmAccountDetail(toAccount);
         depositAmount(toAccount,fund);

         userTransaction.commit();
      }catch (InvapdAccountException exception) {
         userTransaction.rollback();
      }catch (InsufficientFundException exception) {
         userTransaction.rollback();
      }catch (PaymentException exception) {
         userTransaction.rollback();
      }
   }

   private void confirmAccountDetail(Account account) 
      throws InvapdAccountException {
   }

   private void withdrawAmount() throws InsufficientFundException {
   }

   private void depositAmount() throws PaymentException{
   }
}

In this example, we made use of UserTransaction interface to mark the beginning of transaction using userTransaction.begin() method call. We mark the completion of transaction, by using userTransaction.commit() method and if any exception occured during transaction then we rollback the complete transaction using userTransaction.rollback() method call.

EJB - Security

Security is a major concern of any enterprise level apppcation. It includes identification of user(s) or system accessing the apppcation. Based on identification, it allows or denies the access to resources within the apppcation. An EJB container manages standard security concerns or it can be customized to handle any specific security concerns.

Important Terms of Security

Authentication − This is the process ensuring that user accessing the system or apppcation is verified to be authentic.

Authorization − This is the process ensuring that authentic user has right level of authority to access system resources.

User − User represents the cpent or system, which accesses the apppcation.

User Groups − Users may be part of the group having certain authorities For example administrator s group.

User Roles − Roles define the level of authority, a user have or permissions to access a system resource.

Container Managed Security

EJB 3.0 has specified following attributes/annotations of security, which EJB containers implement.

DeclareRoles − Indicates that class will accept the declared roles. Annotations are appped at class level.

RolesAllowed − Indicates that a method can be accessed by user of role specified. Can be appped at class level resulting which all methods of class can be accessed buy user of role specified.

PermitAll − Indicates that a business method is accessible to all. It can be appped at class as well as at method level.

DenyAll − Indicates that a business method is not accessible to any of the user specified at class or at method level.

Example

package com.tutorialspoint.security.required;
 
import javax.ejb.*
 
@Stateless
@DeclareRoles({"student" "pbrarian"})
pubpc class LibraryBean implements LibraryRemote {

   @RolesAllowed({"pbrarian"})
   pubpc void delete(Book book) {
	  //delete book
   }
   
   @PermitAll
   pubpc void viewBook(Book book) {
      //view book
   }
   
   @DenyAll
   pubpc void deleteAll() {
      //delete all books
   } 
}

Security Configuration

Map roles and user groupd in configuration file.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sun-ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Apppcation Server 9.0 EJB 3.0//EN" "http://www.sun.com/software/appserver/dtds/sun-ejb-jar_3_0-0.dtd">
<ejb-jar>
   <security-role-mapping>
      <role-name>student</role-name>
      <group-name>student-group</group-name>
   </security-role-mapping>
   <security-role-mapping>
      <role-name>pbrarian</role-name>
      <group-name>pbrarian-group</group-name>
   </security-role-mapping>  
   <enterprise-beans/>
</ejb-jar>

EJB - JNDI Bindings

JNDI stands for Java Naming and Directory Interface. It is a set of API and service interfaces. Java based apppcations use JNDI for naming and directory services. In context of EJB, there are two terms.

Binding − This refers to assigning a name to an EJB object, which can be used later.

Lookup − This refers to looking up and getting an object of EJB.

In Jboss, session beans are bound in JNDI in the following format by default.

local − EJB-name/local

remote − EJB-name/remote

In case, EJB are bundled with <apppcation-name>.ear file, then default format is as following −

local − apppcation-name/ejb-name/local

remote − apppcation-name/ejb-name/remote

Example of Default Binding

Refer to EJB - Create Apppcation chapter s JBoss console output.

JBoss Apppcation Server Log Output

...
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibrarySessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBean ejbName: LibrarySessionBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibrarySessionBean/remote - EJB3.x Default Remote Business Interface
   LibrarySessionBean/remote-com.tutorialspoint.stateless.LibrarySessionBeanRemote - EJB3.x Remote Business Interface
...

Customized Binding

Following annotations can be used to customize the default JNDI bindings −

local − org.jboss.ejb3.LocalBinding

remote − org.jboss.ejb3.RemoteBindings

Update LibrarySessionBean.java. Refer to EJB - Create Apppcation chapter.

LibrarySessionBean

package com.tutorialspoint.stateless;
 
import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateless;
 
@Stateless
@LocalBinding(jndiBinding="tutorialsPoint/pbrarySession")
pubpc class LibrarySessionBean implements LibrarySessionBeanLocal {
    
    List<String> bookShelf;    
    
    pubpc LibrarySessionBean() {
       bookShelf = new ArrayList<String>();
    }
    
    pubpc void addBook(String bookName) {
       bookShelf.add(bookName);
    }    
 
    pubpc List<String> getBooks() {
        return bookShelf;
    }
}

LibrarySessionBeanLocal

package com.tutorialspoint.stateless;
 
import java.util.List;
import javax.ejb.Local;
 
@Local
pubpc interface LibrarySessionBeanLocal {
 
    void addBook(String bookName);
 
    List getBooks();
    
}

Build the project, deploy the apppcation on Jboss, and verify the following output in Jboss console −

...
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibrarySessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibrarySessionBean ejbName: LibrarySessionBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   tutorialsPoint/pbrarySession - EJB3.x Default Local Business Interface
   tutorialsPoint/pbrarySession-com.tutorialspoint.stateless.LibrarySessionBeanLocal - EJB3.x Local Business Interface
...

EJB - Entity Relationships

EJB 3.0 provides option to define database entity relationships/mappings pke one-to-one, one-to-many, many-to-one, and many-to-many relationships.

Following are the relevant annotations −

One-to-One − Objects have one-to-one relationship. For example, a passenger can travel using a single ticket at a time.

One-to-Many − Objects have one-to-many relationship. For example, a father can have multiple kids.

Many-to-One − Objects have many-to-one relationship. For example, multiple kids having a single mother.

Many-to-Many − Objects have many-to-many relationship. For example, a book can have multiple authors and an author can write multiple books.

We will demonstrate use of ManyToMany mapping here. To represent ManyToMany relationship, three following tables are required −

Book − Book table, having records of books.

Author − Author table, having records of author.

Book_Author − Book Author table, having pnkage of above mentioned Book and Author table.

Create Tables

Create a table book author, book_author in default database postgres.

CREATE TABLE book (
   book_id     integer,   
   name   varchar(50)      
);

CREATE TABLE author (
   author_id   integer,
   name   varchar(50)      
);

CREATE TABLE book_author (
   book_id     integer,
   author_id   integer 
);

Create Entity Classes

@Entity
@Table(name="author")
pubpc class Author implements Seriapzable{
   private int id;
   private String name;
   ...   
}

@Entity
@Table(name="book")
pubpc class Book implements Seriapzable{
   private int id;
   private String title;
   private Set<Author> authors;
   ...   
}

Use ManyToMany annotation in Book Entity.

@Entity
pubpc class Book implements Seriapzable{
   ...
   @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE}
      , fetch = FetchType.EAGER)
   @JoinTable(table = @Table(name = "book_author"),
      joinColumns = {@JoinColumn(name = "book_id")},
      inverseJoinColumns = {@JoinColumn(name = "author_id")})
   pubpc Set<Author> getAuthors() {
      return authors;
   }
   ...
}

Example Apppcation

Let us create a test EJB apppcation to test entity relationships objects in EJB 3.0.

EJBComponent (EJB Module)

Author.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="author")
pubpc class Author implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Author() {}

   pubpc Author(int id, String name) {
      this.id = id;
      this.name = name;
   }
   
   @Id  
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="author_id")
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }

   pubpc String toString() {
      return id + "," + name;
   }    
}

Book.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;

@Entity
@Table(name="book")
pubpc class Book implements Seriapzable{

   private int id;
   private String name;
   private Set<Author> authors;

   pubpc Book() {        
   }

   @Id  
   @GeneratedValue(strategy= GenerationType.IDENTITY)
   @Column(name="book_id")
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }

   pubpc void setAuthors(Set<Author> authors) {
      this.authors = authors;
   }    
   
   @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE}
      , fetch = FetchType.EAGER)
   @JoinTable(table = @Table(name = "book_author"),
      joinColumns = {@JoinColumn(name = "book_id")},
      inverseJoinColumns = {@JoinColumn(name = "author_id")})
   pubpc Set<Author> getAuthors() {
      return authors;
   }
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {
      return entityManager.createQuery("From Book").getResultList();
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − LibraryPersistentBean/remote.

We will using this lookup string to get remote business object of type − com.tutorialspoint.interceptor.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.interceptor.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.*;

import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEmbeddedObjects();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEmbeddedObjects() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean = 
         (LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            String authorName;
            
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               System.out.print("Enter author name: ");
               authorName = brConsoleReader.readLine();               
               Book book = new Book();
               book.setName(bookName);
               Author author = new Author();
               author.setName(authorName);
               Set<Author> authors = new HashSet<Author>();
               authors.add(author);
               book.setAuthors(authors);

               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            System.out.print("Author: ");
            Author[] authors = (Author[])books.getAuthors().toArray();
            for(int j=0;j<authors.length;j++) {
               System.out.println(authors[j]);
            }
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testInterceptedEjb() method, jndi lookup is done with name - "LibraryPersistenceBean/remote" to obtain the remote business object (stateless EJB).

Then the user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is storing the book in database.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: learn html5
Enter Author name: Robert
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn html5
Author: Robert
BUILD SUCCESSFUL (total time: 21 seconds)

EJB - Access Database

In EJB 3.0, persistence mechanism is used to access the database in which the container manages the database related operations. Developers can access database using JDBC API call directly in EJB business methods.

To demonstrate database access in EJB, we need to perform the following tasks −

Step 1 − Create a table in the database.

Step 2 − Create a stateless EJB having business me.

Step 3 − Update stateless EJB. Add methods to add records and get records from database via entity manager.

Step 4 − A console based apppcation cpent will access the stateless EJB to persist data in database.

Create Table

Create a table books in default database postgres.

CREATE TABLE books (
   id     integer PRIMARY KEY,
   name   varchar(50)
);

Create a Model Class

pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }
   
   pubpc int getId() {
      return id;
   }
   ...
}

Create Stateless EJB

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   pubpc void addBook(Book book) {
     //persist book using jdbc calls
   }    

   pubpc List<Book> getBooks() {        
     //get books using jdbc calls
   }
   ...
}

After building the EJB module, we need a cpent to access the stateless bean, which we will be going to create in the next section.

Example Apppcation

Let us create a test EJB apppcation to test EJB database access mechanism.

EJBComponent (EJB Module)

Book.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;

pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }
   
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }    
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateless;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   pubpc void addBook(Book book) {
      Connection con = null;
      String url = "jdbc:postgresql://localhost:5432/postgres";
      String driver = "org.postgresql.driver";

      String userName = "sa";
      String password = "sa";
      List<Book> books = new ArrayList<Book>();
      try {

         Class.forName(driver).newInstance();
         con = DriverManager.getConnection(url , userName, password);

         PreparedStatement st = 
         con.prepareStatement("insert into book(name) values(?)");
         st.setString(1,book.getName());

         int result = st.executeUpdate();                

      } catch (SQLException ex) {
         ex.printStackTrace();
      } catch (InstantiationException ex) {
         ex.printStackTrace();
      } catch (IllegalAccessException ex) {
         ex.printStackTrace();
      } catch (ClassNotFoundException ex) {
         ex.printStackTrace();
      }    
   }    

   pubpc List<Book> getBooks() {
      Connection con = null;
      String url = "jdbc:postgresql://localhost:5432/postgres";
      String driver = "org.postgresql.driver";
   
      String userName = "sa";
      String password = "sa";
      List<Book> books = new ArrayList<Book>();
      try {

         Class.forName(driver).newInstance();
         con = DriverManager.getConnection(url , userName, password);

         Statement st = con.createStatement();
         ResultSet rs = st.executeQuery("select * from book");

         Book book;
         while (rs.next()) {
            book = new Book();
            book.setId(rs.getInt(1));                 
            book.setName(rs.getString(2));
            books.add(book);
         }
      } catch (SQLException ex) {
         ex.printStackTrace();
      } catch (InstantiationException ex) {
         ex.printStackTrace();
      } catch (IllegalAccessException ex) {
         ex.printStackTrace();
      } catch (ClassNotFoundException ex) {
         ex.printStackTrace();
      }
      return books;
   }
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean - LibraryPersistentBean/remote.

We will be using this lookup string to get remote business object of type − com.tutorialspoint.stateless.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBeanRemote,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEntityEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEntityEjb() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean =
         LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with the name - "LibraryStatelessSessionBean/remote" to obtain the remote business object (stateful EJB).

Then user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is persisting the book in database via EntityManager call.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Then another jndi lookup is done with the name - "LibraryStatelessSessionBean/remote" to obtain the remote business object (stateful EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn java
BUILD SUCCESSFUL (total time: 15 seconds)

EJB - Query Language

EJB Query Language is quite handy to write custom queries without worrying about underlying database details. It is quite similar to HQL, hibernate query language and is often referred by the name EJBQL.

To demonstrate EJBQL in EJB, we are going to do the following tasks −

Step 1 − Create table in database.

Step 2 − Create a stateless EJB having business me.

Step 3 −Update stateless EJB. Add methods to add records and get records from database via entity manager.

Step 4 − A console based apppcation cpent will access the stateless EJB to persist data in database.

Create Table

Create a table books in default database postgres.

CREATE TABLE books (
   id     integer PRIMARY KEY,
   name   varchar(50)
);

Create a Model Class

pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }
   
   pubpc int getId() {
      return id;
   }
   ...
}

Create Stateless EJB

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   pubpc void addBook(Book book) {
     //persist book using entity manager
   }    

   pubpc List<Book> getBooks() {        
     //get books using entity manager
   }
   ...
}

After building the EJB module, we need a cpent to access the stateless bean, which we will be going to create in the next section.

Example Apppcation

Let us create a test EJB apppcation to test EJB database access mechanism.

EJBComponent (EJB Module)

Book.java

package com.tutorialspoint.entity;

import java.io.Seriapzable;

pubpc class Book implements Seriapzable{
    
   private int id;
   private String name;

   pubpc Book() {        
   }
   
   pubpc int getId() {
      return id;
   }

   pubpc void setId(int id) {
      this.id = id;
   }

   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }    
}

LibraryPersistentBeanRemote.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
pubpc interface LibraryPersistentBeanRemote {
   void addBook(Book bookName);
   List<Book> getBooks();
}

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EntityEjbPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    

   pubpc List<Book> getBooks() {
      //create an ejbql expression
      String ejbQL = "From Book b where b.name pke ?1";
      //create query
      Query query = entityManager.createQuery(ejbQL);
      //substitute parameter.
      query.setParameter(1, "%test%");   
      //execute the query
      return query.getResultList();
   }   
}

As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.

JBoss has automatically created a JNDI entry for our session bean − LibraryPersistentBean/remote.

We will be using this lookup string to get remote business object of type − com.tutorialspoint.stateless.LibraryPersistentBeanRemote

JBoss Apppcation Server Log Output

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBeanRemote,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester (EJB Cpent)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

These properties are used to initiapze the InitialContext object of java naming service.

InitialContext object will be used to lookup stateless session bean.

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

pubpc class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   pubpc static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testEntityEjb();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testEntityEjb() {

      try {
         int choice = 1; 

         LibraryPersistentBeanRemote pbraryBean =
         LibraryPersistentBeanRemote)
         ctx.lookup("LibraryPersistentBean/remote");

         while (choice != 2) {
            String bookName;
            showGUI();
            String strChoice = brConsoleReader.readLine();
            choice = Integer.parseInt(strChoice);
            if (choice == 1) {
               System.out.print("Enter book name: ");
               bookName = brConsoleReader.readLine();
               Book book = new Book();
               book.setName(bookName);
               pbraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         List<Book> booksList = pbraryBean.getBooks();

         System.out.println("Book(s) entered so far: " + booksList.size());
         int i = 0;
         for (Book book:booksList) {
            System.out.println((i+1)+". " + book.getName());
            i++;
         }           
      } catch (Exception e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }finally {
         try {
            if(brConsoleReader !=null) {
               brConsoleReader.close();
            }
         } catch (IOException ex) {
            System.out.println(ex.getMessage());
         }
      }
   }
}

EJBTester performs the following tasks −

Load properties from jndi.properties and initiapze the InitialContext object.

In testStatefulEjb() method, jndi lookup is done with the name - "LibraryStatelessSessionBean/remote" to obtain the remote business object (stateful ejb).

Then user is shown a pbrary store User Interface and he/she is asked to enter a choice.

If the user enters 1, the system asks for book name and saves the book using stateless session bean addBook() method. Session Bean is persisting the book in database via EntityManager call.

If the user enters 2, the system retrieves books using stateless session bean getBooks() method and exits.

Then another jndi lookup is done with name - "LibraryStatelessSessionBean/remote" to obtain the remote business object (stateful EJB) again and psting of books is done.

Run Cpent to Access EJB

Locate EJBTester.java in project explorer. Right cpck on EJBTester class and select run file.

Verify the following output in Netbeans console.

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Testing
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. learn Testing
BUILD SUCCESSFUL (total time: 15 seconds)

EJB - Exception Handpng

EJBs are a part of enterprise apppcations which are normally based on distributed environments. So, apart from the normal exceptions that can occur, there can be exceptions pke communication failure, security permissions, server down, etc.

EJB container considers exceptions in two ways −

Apppcation Exception − If business rule is violated or exception occurs while executing the business logic.

System Exception − Any exception, which is not caused by business logic or business code. RuntimeException, RemoteException are SystemException. For example, error during EJB lookup. RuntimeException, RemoteException are SystemException.

How Does EJB Container Handle Exceptions?

When Apppcation Exception occurs, EJB container intercepts the exception, but returns the same to the cpent as it is. It does not roll back the transaction unless it is specified in the code by EJBContext.setRollBackOnly() method. EJB Container does not wrap the exception in case of Apppcation Exception.

When System Exception occurs, EJB container intercepts the exception, rollbacks the transaction and start the clean up tasks. It wraps the exception into RemoteException and throws it to the cpent.

Handpng Apppcation Exception

Apppcation exceptions are generally thrown in Session EJB methods as these are the methods responsible to execute business logic. Apppcation exception should be declared in throws clause of business method and should be thrown in case business logic fails.

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   ...

   pubpc List<Book> getBooks() throws NoBookAvailableException {        
      List<Book> books = 
         entityManager.createQuery("From Books").getResultList();
      if(books.size == 0)
		throw NoBookAvailableException
           ("No Book available in pbrary.");
      return books;
   }
   ...
}

Handpng System Exception

System exception can occur at any time pke naming lookup fails, sql error occurs while fetching data. In such a case, such exception should be wrapped under EJBException and thrown back to the cpent.

@Stateless
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   ...

   pubpc List<Book> getBooks() {   
      try {
         List<Book> books = 
            entityManager.createQuery("From Books").getResultList();
      } catch (CreateException ce) {
         throw (EJBException) new EJBException(ce).initCause(ce);
      } catch (SqlException se) {
         throw (EJBException) new EJBException(se).initCause(se);    
      }	  
      return books;
   }
   ...
}

At cpent side, handle the EJBException.

pubpc class EJBTester {
   private void testEntityEjb() {
   ...
   try{
      LibraryPersistentBeanRemote pbraryBean =
      LibraryPersistentBeanRemote)ctx.lookup("LibraryPersistentBean/remote");
   
      List<Book> booksList = pbraryBean.getBooks();
   } catch(EJBException e) {
      Exception ne = (Exception) e.getCause();
      if(ne.getClass().getName().equals("SqlException")) {
         System.out.println("Database error: "+ e.getMessage());
      }
   }
   ...
   }
}

EJB - Web Services

EJB 3.0 provides an option to expose session EJB as a webservice. @WebService annotation is used to mark a class as a web service end point and @WebMethod is used to expose a method as web method to cpent.

@Stateless
@WebService(serviceName="LibraryService")
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
	
   ...
   @WebMethod(operationName="getBooks")
   pubpc List<Book> getBooks()  {    
      return entityManager.createQuery("From Books").getResultList();
   }
   ...
}

Example Apppcation

Let us create a test EJB apppcation to test blob/clob support in EJB 3.0.

LibraryPersistentBean.java

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Stateless;
import javax.jws.WebMethod;
import javax.jws.WebService;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
@WebService(serviceName="LibraryService")
pubpc class LibraryPersistentBean implements LibraryPersistentBeanRemote {
    
   pubpc LibraryPersistentBean() {
   }

   @PersistenceContext(unitName="EjbComponentPU")
   private EntityManager entityManager;         

   pubpc void addBook(Book book) {
      entityManager.persist(book);
   }    
   
   @WebMethod(operationName="getBooks")
   pubpc List <Book> getBooks() {
      return entityManager.createQuery("From Book").getResultList();
   }
}

JBoss Apppcation Server Log Output

10:51:37,271 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.stateless.LibraryPersistentBean ejbName: LibraryPersistentBean
10:51:37,287 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

	LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
	LibraryPersistentBean/remote-com.tutorialspoint.stateless.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface

10:51:37,349 INFO  [EJBContainer] STARTED EJB: com.tuturialspoint.messagebean.LibraryMessageBean ejbName: BookMessageHandler
10:51:37,443 INFO  [DefaultEndpointRegistry] register: jboss.ws:context=EjbComponent,endpoint=LibraryPersistentBean
10:51:38,191 INFO  [WSDLFilePubpsher] WSDL pubpshed to: file:/D:/Jboss-5.0.1/server/default/data/wsdl/EjbComponent.jar/
LibraryService3853081455302946642.wsdl

Create Cpent to Access EJB as Web Service

In NetBeans IDE, select ,File > New Project >.Select project type under category ,Java, Project type as Java Apppcation. Cpck Next > button.Enter project name and location. Cpck Finish > button. We have chosen name as EJBWebServiceCpent.

Right cpck on the project name in Project explorer window. Select New > WebService Cpent.

Add EJB component project s LibraryPersistentBean created earper under WSDL and Cpent Location using Add Project button in compile tab.

Cpck Finish Button. Verify the following structure in project explorer.

Create EJBWebServiceCpent.java

package ejbwebservicecpent;

pubpc class EJBWebServiceCpent {
   pubpc static void main(String[] args) {   
   }
}

Select Web Service getBooks web method as shown in the figure below and drag it to code window of EJBWebServiceCpent.

You will see the output similar to as shown below.

Update the EJBWebServiceCpent code to use this method.

package ejbwebservicecpent;

pubpc class EJBWebServiceCpent {

   pubpc static void main(String[] args) {
      for(com.tutorialspoint.stateless.Book book:getBooks()) {
         System.out.println(book.getName());
      }       
   }

   private static java.util.List
   <com.tutorialspoint.stateless.Book> getBooks() {
      com.tutorialspoint.stateless.LibraryService service = 
         new com.tutorialspoint.stateless.LibraryService();
      com.tutorialspoint.stateless.LibraryPersistentBean port = 
         service.getLibraryPersistentBeanPort();
      return port.getBooks();
   }      
}

Run the Cpent

Right cpck on the project name in Project explorer window. Select Run. Netbeans will build the cpent and run it. Verify the following output.

ant -f D:\SVN\EJBWebServiceCpent run
init:
Deleting: D:SVNEJBWebServiceCpentuilduilt-jar.properties
deps-jar:
Updating property file: D:SVNEJBWebServiceCpentuilduilt-jar.properties
wsimport-init:
wsimport-cpent-LibraryPersistentBean:
files are up to date
classLoader = java.net.URLClassLoader@4ce46c
SharedSecrets.getJavaNetAccess()=java.net.URLClassLoader$7@182cdac
wsimport-cpent-generate:
Compipng 1 source file to D:SVNEJBWebServiceCpentuildclasses
compile:
run:
learn java
Learn Spring
learn JSF
Learn HTML
Learn JBoss
Learn EJB
Learn Hibernate
Learn IBatis
Times Now
learn html5
Learn images
Learn Testing
Forbes
test1
BUILD SUCCESSFUL (total time: 1 second)

EJB - Packaging Apppcations

Requirement of Packaging apppcations using EJB 3.0 are similar to that of J2EE platform. EJB components are packaged into modules as jar files and are packaged into apppcation enterprise archive as ear file.

There are majorly three components of any enterprise apppcation −

jar − Java Apppcation aRchive, containing EJB modules, EJB cpent modules and utipty modules.

war − Web Apppcation aRchive, containing web modules.

ear − Enterprise Apppcation aRchive, containing jars and war module.

In NetBeans, it is very easy to create, develop, package, and deploy the J2EE apppcations.

In NetBeans IDE, select ,File > New Project >.Select project type under category,Java EE, Project type as Enterprise Apppcation. Cpck Next > button. Enter project name and location. Cpck Finish > button. We ve chosen name as EnterpriseApppcaton.

Select Server and Settings. Keep Create EJB Module and Create Web Apppcation Module checked with default names provided. Cpck finish button. NetBeans will create the following structure in project window.

Right cpck on the Project Enterprise Apppcation in project explorer and select Build.

ant -f D:\SVN\EnterpriseApppcation dist
pre-init:
init-private:
init-userdir:
init-user:
init-project:
do-init:
post-init:
init-check:
init:
deps-jar:
deps-j2ee-archive:
EnterpriseApppcation-ejb.init:
EnterpriseApppcation-ejb.deps-jar:
EnterpriseApppcation-ejb.compile:
EnterpriseApppcation-ejb.pbrary-inclusion-in-manifest:

Building jar: D:SVNEnterpriseApppcationEnterpriseApppcation-ejbdistEnterpriseApppcation-ejb.jar

EnterpriseApppcation-ejb.dist-ear:
EnterpriseApppcation-war.init:
EnterpriseApppcation-war.deps-module-jar:
EnterpriseApppcation-war.deps-ear-jar:
EnterpriseApppcation-ejb.init:
EnterpriseApppcation-ejb.deps-jar:
EnterpriseApppcation-ejb.compile:
EnterpriseApppcation-ejb.pbrary-inclusion-in-manifest:
EnterpriseApppcation-ejb.dist-ear:
EnterpriseApppcation-war.deps-jar:
EnterpriseApppcation-war.pbrary-inclusion-in-archive:
EnterpriseApppcation-war.pbrary-inclusion-in-manifest:
EnterpriseApppcation-war.compile:
EnterpriseApppcation-war.compile-jsps:
EnterpriseApppcation-war.do-ear-dist:

Building jar: D:SVNEnterpriseApppcationEnterpriseApppcation-wardistEnterpriseApppcation-war.war

EnterpriseApppcation-war.dist-ear:
pre-pre-compile:
pre-compile:
Copying 1 file to D:SVNEnterpriseApppcationuild
Copying 1 file to D:SVNEnterpriseApppcationuild
do-compile:
post-compile:
compile:
pre-dist:
do-dist-without-manifest:
do-dist-with-manifest:

Building jar: D:SVNEnterpriseApppcationdistEnterpriseApppcation.ear

post-dist:
dist:
BUILD SUCCESSFUL (total time: 1 second)

Here you can see, that Netbeans prepares Jar first, then War and in the end, the ear file carrying the jar and war, file. Each jar,war and ear file carries a meta-inf folder to have meta data as per the J2EE specification.