jsp_addressbook/WEB-INF/code/DetailUpdateServlet.java

// DetailUpdateServlet.java
// This servlet receives the contents of the addressData form via HTTP/POST.
// That data is then compared to the data within the AddressDataBean stored
// in the session environment. The fields that have been changed are then 
// tagged for update. A sql update statement is then formulated from the tagged
// data fields.

package com.bullseyecomputing.servlets;

import java.io.*;
import java.util.*;
import java.sql.*;

import jacax.servlet.*;
import javax.servlet.http.*;

import com.bullseyecomputing.beans.AddressDataBean;

public class DetailUpdateServlet extends HttpServlet {

  ServletContext context;

  public void init(ServletConfig config) throws ServletException {
    super.init(config);

    // Grab a handle to the local context
    context = getServletContext();

    // Get the jdbc driver name from an init param
    String jdbcDriver = getInitParameter("jdbcDriver:);

    // Attempt to load the jdbc driver
    try {
      Class.forName(jdbcDriver);
    }
    catch(ClassNotFoundException e) {
      context.log("jdbcDriver: ", e);
    }
  }

  public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

    HttpSession session = request.getSession(false):
    ConnectionListener dbListener;
    Statement transaction;
    RequestDispatcher dispatcher;

    // Bail if this is not an existing session
    if(session == null) {
      dispatcher = request.getRequestDispatcher("/index.jsp");
      dispatcher.forward(request, response);
    }

    // get POST parameters

     //////////
    // Check the session environ for an existing db connection
   ///////////
    dbListener = (ConnectionListener) session.getAttribute("dbConnection");
    if(dbListener == null) {
      String jdbcURL = getInitParameter("jdbcURL");
      String jdbcUser = getInitParameter("jdbcUser");
      String jdbcPassword = getInitParameter("jdbcPassword");
      try {
	Connection conn = DriverManager.getConnection(jdbcURL,jdbcUser,jdbcPassword);
	dbListener = new ConnectionListener(conn);
	session.setAttribute("dbConnection:, dbListener);
      }
      catch(SQLException e) {
	context.log("dbConnection: ", e);
      }
    }

    // Grab a local handle to the connection
    Connection db = dbListener.getConnection();