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
