Reuse of database connection in jsp/servlet

Reuse of database connection in jsp/servlet:

Hope the below example will help you for reuse of database connection 

Servlet class:

package com.jspcr.servlets;

import java.io.*;

import java.sql.*;

import javax.servlet.*;

import javax.servlet.http.*;

import javax.servlet.jsp.*;

/**

* An example of a JSP superclass that can be selected with

* the extends attribute of the page

* directive.  This servlet automatically loads the

* JDBC-ODBC driver class when initialized and establishes

* a connection to the USDA nutrient database.

*/

public abstract class NutrientDatabaseServlet

   extends HttpServlet

   implements HttpJspPage

{

   protected Connection con;

   /**

   * Initialize a servlet with the driver

   * class already loaded and the database

   * connection established.

   */

   public void init(ServletConfig config)

      throws ServletException

   {

      super.init(config);

      try {

         Class.forName("com.mysql.jdbc.Driver");

         con = DriverManager.getConnection("jdbc:mysql://localhost/usda15");

      }

      catch (Exception e) {

         throw new UnavailableException(e.getMessage());

      }

      jspInit();

   }

   /**

   * Closes the database connection when

   * the servlet is unloaded.

   */

   public void destroy()

   {

      try {

         if (con != null) {

            con.close();

            con = null;

         }

      }

      catch (Exception ignore) {}

      jspDestroy();

      super.destroy();

   }

   /**

   * Called when the JSP is loaded.

   * By default does nothing.

   */

   public void jspInit() {}

   /**

   * Called when the JSP is unloaded.

   * By default does nothing.

   */

   public void jspDestroy() {}

   /**

   * Invokes the JSP's _jspService method.

   */

   public final void service(

         HttpServletRequest request,

         HttpServletResponse response)

      throws ServletException, IOException

   {

      _jspService(request, response);

   }

   /**

   * Handles a service request.

   */

   public abstract void _jspService(

         HttpServletRequest request,

         HttpServletResponse response)

      throws ServletException, IOException;

} 

JSP Page:

<%--

  Copyright (c) 2002 by Phil Hanna

  All rights reserved.

  

  You may study, use, modify, and distribute this

  software for any purpose provided that this

  copyright notice appears in all copies.

  

  This software is provided without warranty

  either expressed or implied.

--%>

<%@ page extends="com.jspcr.servlets.NutrientDatabaseServlet" %>

<%--

   This JSP page subclasses the NutrientDatabaseServlet

   parent class, which automatically loads the

   database driver and establishes the connection.

--%>

<%@ page import="java.io.*,java.sql.*" %>

Food Groups

CodeDescription

<%

   // Execute a query

   Statement stmt = con.createStatement();

   String sql = "SELECT * FROM FD_GROUP ORDER BY FDGP_DESC";

   ResultSet rs = stmt.executeQuery(sql);

   while (rs.next()) {

      String code = rs.getString(1);

      String desc = rs.getString(2);

%>

http://astore.amazon.com/httpsjavatop1-20

   <%= code %>

   <%= desc %>

<%

   }

   

   // Close the database objects

   rs.close();

   stmt.close();

%>