jsp_addressbook/WEB-INF/code/DetailQueryServlet.java

// DetailQueryServlet.java
// This servlet receives an addressee identifier as a request argument,
// and makes the required query/(queries) to retrieve the addressee's
// detail info. This info is loaded into a DataBean that is then stored
// in the session environment. The servlet then redirects to the correct
// JSP for display.

package com.bullseyecomputing.servlets;

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

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

import com.bullseyecomputing.beans.AddressDataBean;

public class DetailQueryServlet 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 name of the jdbc driver from an init param
    String jdbcDriver = getInitParameter("jdbcDriver");
    // Now try to load the driver
    try {
      Class.forName(jdbcDriver);
    }
    catch(ClassNotFoundException e) {
      context.log("jdbcDriver: ", e);
    }
  }

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

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

    // Bail if we're not part of a session
    if(session == null) {
      dispatcher = context.getRequestDispatcher("/index.jsp");
      dispatcher.forward(request, response);
    }

    // Look for an existing db connection in the session environment
    dbListener = (ConnectionListener) session.getAttribute("dbConnection");
    // Create one if it's not there
    if(dbListener == null) {
      // Load the params from init
      String jdbcURL = getInitParameter("jdbcURL");
      String jdbcUser = getInitParameter("jdbcUser");
      String jdbcPassword = getInitParameter("jdbcPassword");
      // Attempt to make the connection
      try {
	Connection conn = DriverManager.getConnection(jdbcURL,jdbcUser,jdbcPassword);
	dbListener = new ConnectionListener(conn);
	// Push the new connection into the session environment
	session.setAttribute("dbConnection", dbListener);
      }
      catch(SQLException e) {
	context.log("dbConnection", e);
      }
    }

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

    // Build the query based on init and request parameters
    String selected = getInitParameter("selected");
    String table = getInitParameter("table");
    String id = request.getParameter("id");

    StringBuffer query = new StringBuffer();
    query.append("select ").append(selected);
    query.append(" from ").append(table);
    query.append(" where id = ").append(id);
  //
    context.log(query.toString());
  //

    // Execute the query
    try {
      transaction = db.createStatement();
      results = transaction.executeQuery(query.toString());

      // move to the first (and only) record
      results.next();

      // Create a DataBean to store the results
      AddressDataBean address = new AddressDataBean();

      // Push the data into the DataBean
      address.setIdNumber(Integer.toString(results.getInt(1)));
      address.setName(results.getString(2));
      address.setStreet(results.getString(3));
      address.setCity(results.getString(4));
      address.setState(results.getString(5));
      address.setZipcode(results.getString(6));
      address.setPlus4(results.getString(7));
      address.setAreacode(results.getString(8));
      address.setPhone(results.getString(9));

      // Push the AddressBean into the session environment
      session.setAttribute("address.data", address);

      // Close the database transaction
      results.close();
      transaction.close();
    }
    catch(SQLException e) {
      context.log("DetailQueryServlet: Error during SQL transaction", e);
    }

    // Forward to the corresponding JSP
    dispatcher = request.getRequestDispatcher("addressData.jsp");
    dispatcher.forward(request, response);
  }
}