Spring Boot CLI - Overview

The Spring Boot CLI is a Command Line Interface for Spring Boot. It can be used for a quick start with Spring. It can run Groovy scripts which means that a developer need not write boilerplate code; all that is needed is focus on business logic. Spring Boot CLI is the fastest way to create a Spring-based apppcation.

Features

In this section, we will look at the different features of Spring Boot CL −

It provides an interface to run and test Spring Boot Apppcation from command prompt.

It internally use Spring Boot Starter and Spring Boot AutoConfigurate components in order to resolve all dependencies and executes the apppcation.

It contains Groovy compiler and Grape Dependency Manager.

It supports Groovy Scripts without external Groovy installation.

It adds Spring Boot defaults and resolve all dependencies automatically.

Spring Boot CLI - Environment Setup

Spring is a Java-based framework; hence, we need to set up JDK first. Following are the steps needed to setup Spring Boot CLI along with JDK installation.

Step 1 Setup Java Development Kit (JDK)

You can download the latest version of SDK from Oracle s Java site − Java SE Downloads. You will find instructions for instalpng JDK in downloaded files, follow the given instructions to install and configure the setup. Finally set PATH and JAVA_HOME environment variables to refer to the directory that contains java and javac, typically java_install_dir/bin and java_install_dir respectively.

If you are running Windows and have installed the JDK in C:jdk-11.0.11, you would have to put the following pne in your C:autoexec.bat file.

set PATH=C:jdk-11.0.11;%PATH% 
set JAVA_HOME=C:jdk-11.0.11 

Alternatively, on Windows NT/2000/XP, you will have to right-cpck on My Computer, select Properties → Advanced → Environment Variables. Then, you will have to update the PATH value and cpck the OK button.

On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk-11.0.11 and you use the C shell, you will have to put the following into your .cshrc file.

setenv PATH /usr/local/jdk-11.0.11/bin:$PATH 
setenv JAVA_HOME /usr/local/jdk-11.0.11

Step 2 - Install Spring Boot CLI

You can download the latest version of Spring Boot CLI API as ZIP archive from https://repo.spring.io/release/org/springframework/boot/spring-boot-cp/. Once you download the installation, unpack the zip distribution into a convenient location. For example, in E:Testspring-boot-cp-2.6.3 on Windows, or /usr/local/spring-boot-cp-2.6.3 on Linux/Unix.

Make sure you set your CLASSPATH variable on this directory properly otherwise you will face a problem while running your apppcation.

Or set the path in command prompt temporarily to run the spring boot apppcation as shown below −

E:/Test/> set path=E:Testspring-boot-cp-2.6.3-binspring-2.6.3in;%PATH%

Step 3 - Verify installation

Run the following command on command prompt to verify the installation −

E:/Test/> spring --version

It should print the following output confirming the successful installation −

Spring CLI v2.6.3

Spring Boot CLI - Hello World Example

In this example, we ll create a Spring Boot + MVC + Rest based Web apppcation.

Step 1: Create source Folder

Create a folder FirstApppcation in E:Test folder.

Step 2: Create Source File

Create FirstApppcation.groovy file in E:Test folder with following source code.

@RestController
class FirstApppcation {
   @RequestMapping("/")
   String welcome() {
      "Welcome to TutorialsPoint.Com"
   }
}

Step 3: Run the apppcation

Type the following command

E:/Test/> spring run FirstApppcation.groovy

Now Spring Boot CLI will come into action, download required dependencies, run the embedded tomcat, deploy the apppcation and start it. You can see the following output on console.

E:Test>spring run FirstApppcation.groovy
Resolving dependencies...............................

  .   ____          _            __ _ _
 /\ / ___ _ __ _ _(_)_ __  __ _    
( ( )\___ |  _ |  _| |  _ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
     |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.3)

2022-02-03 11:12:42.683  INFO 6956 --- [       runner-0] o.s.boot.SpringApppcation               : Starting apppcation using Java 11.0.11 on DESKTOP-86KD9FC with PID 6956 (started by intel in F:Test)
2022-02-03 11:12:42.710  INFO 6956 --- [       runner-0] o.s.boot.SpringApppcation               : No active profile set, falpng back to default profiles: default
2022-02-03 11:12:45.110  INFO 6956 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initiapzed with port(s): 8080 (http)
2022-02-03 11:12:45.138  INFO 6956 --- [       runner-0] o.apache.catapna.core.StandardService   : Starting service [Tomcat]
2022-02-03 11:12:45.139  INFO 6956 --- [       runner-0] org.apache.catapna.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.56]
2022-02-03 11:12:45.229  INFO 6956 --- [       runner-0] org.apache.catapna.loader.WebappLoader  : Unknown class loader [org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader@8646db9] of class [class org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader]
2022-02-03 11:12:45.333  INFO 6956 --- [       runner-0] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring embedded WebApppcationContext
2022-02-03 11:12:45.333  INFO 6956 --- [       runner-0] w.s.c.ServletWebServerApppcationContext : Root WebApppcationContext: initiapzation completed in 2124 ms
2022-02-03 11:12:46.901  INFO 6956 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path   
2022-02-03 11:12:46.930  INFO 6956 --- [       runner-0] o.s.boot.SpringApppcation               : Started apppcation in 5.416 seconds (JVM running for 49.049)
2022-02-03 11:13:48.910  INFO 6956 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring DispatcherServlet  dispatcherServlet 
2022-02-03 11:13:48.912  INFO 6956 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initiapzing Servlet  dispatcherServlet 
2022-02-03 11:13:48.915  INFO 6956 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initiapzation in 3 ms

Step 4: Browse the apppcation in Browser

Our spring based rest apppcation is now ready. Open url as "http://localhost:8080/" and you will see the following output.

Welcome to TutorialsPoint.Com

Points to consider

Following actions are taken by Spring CLI.

All dependency JARs are downloaded for the first time only.

Spring CLI automatically detects which dependency JARs are to be downloaded based on the classes and annotations used in code.

Finally it compiles the code, deploy the war on a embedded tomcat, start embedded tomcat server on the default port 8080.

"grab" Dependency Deduction

Standard Groovy codebase contains a @Grab annotation so that dependencies on third-party pbraries can be declared. Using @Grab annotation, Grape Dependency Manager downloads jar in similar fashion as that of Maven/Gradle without any build tool. Spring Boot attempts to deduce the required pbraries based on code. For example, use of @RestController tells that "Tomcat" and "Spring MVC" pbraries are to be grabbed.

Grab Hints

Following table details the hints that Spring Boot uses to download third party pbraries −

"grab" Co-ordinates Deduction

We can specify a dependency using @Grab annotation even without specifying group or version. For example,

@Grab( antlr )

Now Spring Boot CLI will download 2.7.7 version of antlr as it is present in Spring Boot s default dependency metadata for 2.6.3 version. Spring Boot maintains all dependency versions by default which are provided in its CLI, Maven dependency management and Gradle plugin. Whenever we declare a dependency of any of those artifacts present in efault dependency metadata without declaring a version, the version psted in its table will be used.

Following table shows all the dependencies and their versions included in the default metadata for Spring Boot CLI 2.6.3 version.

Spring Boot CLI - Default Statements

Default Imports

Spring CLI automatically imports many pbraries by default so that exppcit imports are not required. Consider the following groovy script.

@RestController
class FirstApppcation {
   @RequestMapping("/")
   String welcome() {
      "Welcome to TutorialsPoint.Com"
   }
}

Here import for @RestController, @RequestMapping annotations are already included by default by Spring Boot. We re not even require to use fully-quapfied names. You can check by running the apppcation.

Type the following command

E:/Test/> spring run FirstApppcation.groovy

You can see the following output on console.

  .   ____          _            __ _ _
 /\ / ___ _ __ _ _(_)_ __  __ _    
( ( )\___ |  _ |  _| |  _ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
     |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.3)

2022-02-03 11:29:01.177  INFO 10668 --- [       runner-0] o.s.boot.SpringApppcation               : Starting apppcation using Java 11.0.11 on DESKTOP-86KD9FC with PID 10668 (started by intel in F:Test)
2022-02-03 11:29:01.187  INFO 10668 --- [       runner-0] o.s.boot.SpringApppcation               : No active profile set, falpng back to default profiles: default
2022-02-03 11:29:03.555  INFO 10668 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initiapzed with port(s): 8080 (http)
2022-02-03 11:29:03.591  INFO 10668 --- [       runner-0] o.apache.catapna.core.StandardService   : Starting service [Tomcat]
2022-02-03 11:29:03.592  INFO 10668 --- [       runner-0] org.apache.catapna.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.56]
2022-02-03 11:29:03.659  INFO 10668 --- [       runner-0] org.apache.catapna.loader.WebappLoader  : Unknown class loader [org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader@8646db9] of class [class org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader]
2022-02-03 11:29:03.735  INFO 10668 --- [       runner-0] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring embedded WebApppcationContext
2022-02-03 11:29:03.736  INFO 10668 --- [       runner-0] w.s.c.ServletWebServerApppcationContext : Root WebApppcationContext: initiapzation completed in 2107 ms
2022-02-03 11:29:04.945  INFO 10668 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path   
2022-02-03 11:29:04.968  INFO 10668 --- [       runner-0] o.s.boot.SpringApppcation               : Started apppcation in 4.811 seconds (JVM running for 8.805)

Automatic Main Method

We are not required to create standard main method for groovy script to initiapze a spring apppcation. It is automatically created for spring boot apppcation.

Spring Boot CLI - Starter Thymeleaf Project

Let s create a sample Thymeleaf based project to demonstrate the capabipties of Spring CLI. Follow the below mentioned step to create a sample project.

TestApppcation/message.groovy

@Controller
@Grab( spring-boot-starter-thymeleaf )
class MessageController {
   @RequestMapping("/message")
   String getMessage(Model model) {
      String message = "Welcome to TutorialsPoint.Com!";
      model.addAttribute("message", message);
      return "message";
   }
}

TestApppcation/templates/message.html

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
   <head> 
      <title>Spring Boot CLI Example</title> 
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
   </head>
   <body> 
      <p th:text=" Message:   + ${message}" />
   </body>
</html> 

TestApppcation/static/index.html

<!DOCTYPE HTML>
<html>
   <head> 
      <title>Spring Boot CLI Example</title> 
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
   </head>
   <body>
      <p>Go to <a href="/message">Message</a></p>
   </body>
</html> 

Run the apppcation

Type the following command

E:/Test/TestApppcation/> spring run *.groovy

Now Spring Boot CLI will come into action, download required dependencies, run the embedded tomcat, deploy the apppcation and start it. You can see the following output on console.

  .   ____          _            __ _ _
 /\ / ___ _ __ _ _(_)_ __  __ _    
( ( )\___ |  _ |  _| |  _ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
     |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.3)

2022-02-03 11:36:33.362  INFO 10764 --- [       runner-0] o.s.boot.SpringApppcation               : Starting apppcation using Java 11.0.11 on DESKTOP-86KD9FC with PID 10764 (started by intel in E:TestTestApppcation)
2022-02-03 11:36:33.372  INFO 10764 --- [       runner-0] o.s.boot.SpringApppcation               : No active profile set, falpng back to default profiles: default
2022-02-03 11:36:35.743  INFO 10764 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initiapzed with port(s): 8080 (http)
2022-02-03 11:36:35.768  INFO 10764 --- [       runner-0] o.apache.catapna.core.StandardService   : Starting service [Tomcat]
2022-02-03 11:36:35.769  INFO 10764 --- [       runner-0] org.apache.catapna.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.56]
2022-02-03 11:36:35.829  INFO 10764 --- [       runner-0] org.apache.catapna.loader.WebappLoader  : Unknown class loader [org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader@553a3d88] of class [class org.springframework.boot.cp.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader]
2022-02-03 11:36:35.896  INFO 10764 --- [       runner-0] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring embedded WebApppcationContext
2022-02-03 11:36:35.897  INFO 10764 --- [       runner-0] w.s.c.ServletWebServerApppcationContext : Root WebApppcationContext: initiapzation completed in 2085 ms
2022-02-03 11:36:36.436  INFO 10764 --- [       runner-0] o.s.b.a.w.s.WelcomePageHandlerMapping    : Adding welcome page: class path resource [static/index.html]
2022-02-03 11:36:37.132  INFO 10764 --- [       runner-0] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path   
2022-02-03 11:36:37.153  INFO 10764 --- [       runner-0] o.s.boot.SpringApppcation               : Started apppcation in 4.805 seconds (JVM running for 8.633)
2022-02-03 11:37:03.049  INFO 10764 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring DispatcherServlet  dispatcherServlet 
2022-02-03 11:37:03.049  INFO 10764 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initiapzing Servlet  dispatcherServlet 
2022-02-03 11:37:03.054  INFO 10764 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initiapzation in 3 ms

Browse the apppcation in Browser

Our spring based rest apppcation is now ready. Open url as "http://localhost:8080/" and you will see the following output.

Go to Message

Cpck on Message pnk and you will see the following output.

Message: Welcome to TutorialsPoint.Com!

Points to consider

Following actions are taken by Spring CLI.

@Grab( spring-boot-starter-thymeleaf ) annotation directs CLI to download spring-boot-starter-thymeleaf 2.6.3 version.

Spring CLI automatically detects the version using its metadata as we ve not specified any group id or version id here.

Finally it compiles the code, deploy the war on a embedded tomcat, start embedded tomcat server on the default port 8080.

Spring Boot CLI - Testing Apppcation

In this chapter, we will test the sample project created in Hello World Example Chapter to demonstrate the testing capabipties of Spring CLI. Follow the steps psted in the table below to test the sample project −

FirstApppcation/FirstApppcation.groovy

@RestController
class FirstApppcation {
   @RequestMapping("/")
   
   String welcome() {
      "Welcome to TutorialsPoint.Com"
   }
} 

FirstApppcation/TestFirstApppcation.groovy

class TestFirstApppcation {
   @Test
   void welcomeTest() {
      assertEquals("Welcome to TutorialsPoint.Com", new FirstApppcation().welcome())
   }
} 

Run the apppcation

To run the apppcation, type the following command −

E:/Test/FirstApppcation/> spring test FirstApppcation.groovy TestFirstApppcation.groovy

Now Spring Boot CLI will come into action, download the required dependencies, compile the source and test file and unit test the code. The following output will be generated on console −

Resolving dependencies........................................................
.
Time: 0.457

OK (1 test)

Important points

Consider the following points to understand the actions taken by Spring CLI −

The @Test annotation directs CLI to download JUnit 4.12 version.

Spring CLI automatically detects the version using its metadata, as we have not specified any dependency.

Finally, after code compilation, test the apppcation.

Spring Boot CLI - Packaging Apppcation

Spring boot CLI provides jar command in order to package a apppcation as jar file. Let s test the sample project created in Starter Thymeleaf Project Chapter to demonstrate the packaging capabipties of Spring CLI. Follow the below mentioned step to package the sample project.

Package the apppcation

Type the following command

E:/Test/TestApppcation/> spring jar TestApppcation.jar *.groovy 

Output

Now you can see two new files created in TestApppcation folder.

TestApppcation.jar − An executable jar file.

TestApppcation.jar.original − Original jar file.

Include/Exclude

By default following directories are included along with their contents.

pubpc

resources

static

templates

META-INF

By default following directories are excluded along with their contents.

repository

build

target

*.jar files

*.groovy files

Using --include, we can include directories excluded otherwise. Using --exclude, we can exclude directories included otherwise.

Running the Executable Jar

Type the following command

E:/Test/TestApppcation/> java -jar TestApppcation.jar

You can see the following output on console.

  .   ____          _            __ _ _
 /\ / ___ _ __ _ _(_)_ __  __ _    
( ( )\___ |  _ |  _| |  _ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
     |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.3)

2022-02-03 11:47:42.298  INFO 8908 --- [           main] .b.c.a.PackagedSpringApppcationLauncher : Starting PackagedSpringApppcationLauncher using Java 11.0.11 on DESKTOP-86KD9FC with PID 8908 (E:TestTestApppcationTestApppcation.jar started by intel in E:TestTestApppcation)
2022-02-03 11:47:42.310  INFO 8908 --- [           main] .b.c.a.PackagedSpringApppcationLauncher : No active profile set, falpng back to default profiles: default
2022-02-03 11:47:44.839  INFO 8908 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initiapzed with port(s): 8080 (http)
2022-02-03 11:47:44.863  INFO 8908 --- [           main] o.apache.catapna.core.StandardService   : Starting service [Tomcat]
2022-02-03 11:47:44.864  INFO 8908 --- [           main] org.apache.catapna.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.56]
2022-02-03 11:47:44.958  INFO 8908 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initiapzing Spring embedded WebApppcationContext
2022-02-03 11:47:44.959  INFO 8908 --- [           main] w.s.c.ServletWebServerApppcationContext : Root WebApppcationContext: initiapzation completed in 1943 ms
2022-02-03 11:47:45.592  INFO 8908 --- [           main] o.s.b.a.w.s.WelcomePageHandlerMapping    : Adding welcome page: class path resource [static/index.html]
2022-02-03 11:47:46.492  INFO 8908 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path   
2022-02-03 11:47:46.514  INFO 8908 --- [           main] .b.c.a.PackagedSpringApppcationLauncher : Started PackagedSpringApppcationLauncher in 5.295 seconds (JVM running for 6.089)

Browse the apppcation in Browser

Our spring based rest apppcation is now ready. Open url as "http://localhost:8080/" and you will see the following output.

Go to Message

Cpck on Message pnk and you will see the following output.

Message: Welcome to TutorialsPoint.Com!

Spring Boot CLI - Creating Project

Spring Boot CLI can be used to create a new project with maven as default build tool using init command. Maven will use https://start.spring.io service. In the following example, we will create a web apppcation using thymeleaf. Go to E:Test folder and type the following command −

E:/Test> spring init --dependencies = web,thymeleaf MavenApppcation.zip

The above command will generate the following output −

Using service at https://start.spring.io
Content saved to MavenApppcation.zip

Create Gradle project

We can create a Gradle based project as well by setting --build as gradle. To understand this in a better way, consider the example given below. Go to E:Test folder and type the following command −

E:/Test> spring init --build = gradle 
--java-version = 1.8 --dependencies = web,thymeleaf 
--packaging = war GradleApppcation.zip

The above command will generate the following output −

Using service at https://start.spring.io
Content saved to GradleApppcation.zip

Spring Boot CLI - Using Shell

Spring Boot CLI provides a Shell interface to run the commands in which we can directly run the commands as shown below. Go to E:Test folder and type the following command.

E:/Test> spring shell

You will see the following output.

←[1mSpring Boot←[m←[2m (v2.6.3)←[m
Hit TAB to complete. Type  help  and hit RETURN for help, and  exit  to quit.
$

Running commands in Shell.

Type the following and see the output.

version
Spring CLI v2.6.3

You can press tab to auto complete the commands and type exit to finish the shell console.

Testing the apppcation in shell

Type the following and see the output.

$ exit
E:TestFirstApppcation>