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Servlets - Database Access

This tutorial assumes you have understanding on how JDBC apppcation works. Before starting with database access through a servlet, make sure you have proper JDBC environment setup along with a database.

For more detail on how to access database using JDBC and its environment setup you can go through our JDBC Tutorial.

To start with basic concept, let us create a simple table and create few records in that table as follows −

Create Table

To create the Employees table in TEST database, use the following steps −

Step 1

Open a Command Prompt and change to the installation directory as follows −

C:>
C:>cd Program FilesMySQLin
C:Program FilesMySQLin>

Step 2

C:Program FilesMySQLin>mysql -u root -p
Enter password: ********
mysql>

Step 3

Create the table Employee in TEST database as follows −

mysql> use TEST;
mysql> create table Employees (
   id int not null,
   age int not null,
   first varchar (255),
   last varchar (255)
);
Query OK, 0 rows affected (0.08 sec)
mysql>

Create Data Records

Finally you create few records in Employee table as follows −

mysql> INSERT INTO Employees VALUES (100, 18,  Zara ,  Ap );
Query OK, 1 row affected (0.05 sec)
 
mysql> INSERT INTO Employees VALUES (101, 25,  Mahnaz ,  Fatma );
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (102, 30,  Zaid ,  Khan );
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (103, 28,  Sumit ,  Mittal );
Query OK, 1 row affected (0.00 sec)
 
mysql>

Accessing a Database

Here is an example which shows how to access TEST database using Servlet.

// Loading required pbraries
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
 
pubpc class DatabaseAccess extends HttpServlet{

   pubpc void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
   
      // JDBC driver name and database URL
      static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
      static final String DB_URL="jdbc:mysql://localhost/TEST";

      //  Database credentials
      static final String USER = "root";
      static final String PASS = "password";

      // Set response content type
      response.setContentType("text/html");
      PrintWriter out = response.getWriter();
      String title = "Database Result";
      
      String docType =
         "<!doctype html pubpc "-//w3c//dtd html 4.0 " + "transitional//en">
";
      
      out.println(docType +
         "<html>
" +
         "<head><title>" + title + "</title></head>
" +
         "<body bgcolor = "#f0f0f0">
" +
         "<h1 apgn = "center">" + title + "</h1>
");
      try {
         // Register JDBC driver
         Class.forName("com.mysql.jdbc.Driver");

         // Open a connection
         Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);

         // Execute SQL query
         Statement stmt = conn.createStatement();
         String sql;
         sql = "SELECT id, first, last, age FROM Employees";
         ResultSet rs = stmt.executeQuery(sql);

         // Extract data from result set
         while(rs.next()){
            //Retrieve by column name
            int id  = rs.getInt("id");
            int age = rs.getInt("age");
            String first = rs.getString("first");
            String last = rs.getString("last");

            //Display values
            out.println("ID: " + id + "<br>");
            out.println(", Age: " + age + "<br>");
            out.println(", First: " + first + "<br>");
            out.println(", Last: " + last + "<br>");
         }
         out.println("</body></html>");

         // Clean-up environment
         rs.close();
         stmt.close();
         conn.close();
      } catch(SQLException se) {
         //Handle errors for JDBC
         se.printStackTrace();
      } catch(Exception e) {
         //Handle errors for Class.forName
         e.printStackTrace();
      } finally {
         //finally block used to close resources
         try {
            if(stmt!=null)
               stmt.close();
         } catch(SQLException se2) {
         } // nothing we can do
         try {
            if(conn!=null)
            conn.close();
         } catch(SQLException se) {
            se.printStackTrace();
         } //end finally try
      } //end try
   }
}

Now let us compile above servlet and create following entries in web.xml

....
<servlet>
   <servlet-name>DatabaseAccess</servlet-name>
   <servlet-class>DatabaseAccess</servlet-class>
</servlet>
 
<servlet-mapping>
   <servlet-name>DatabaseAccess</servlet-name>
   <url-pattern>/DatabaseAccess</url-pattern>
</servlet-mapping>
....

Now call this servlet using URL http://localhost:8080/DatabaseAccess which would display following response −

Database Result
ID: 100, Age: 18, First: Zara, Last: Ap
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 28, First: Sumit, Last: Mittal