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444

Chapter 17 Using Applets As Servlet Front Ends

HTTP (i.e., by using a URL of the form 

http://...

 to request the page

from a Web server). Loading it directly off your disk through a 

file:

 URL

fails since the applet connects back to its home site to contact the servlet.

Besides, 

URLConnection

 fails for non HTTP applets in general. 

Listing 17.4 ShowQueries.java 

import java.applet.Applet;

import java.awt.*;

import java.awt.event.*;

import java.net.*;

/** Applet reads arrays of strings packaged inside

 *  a QueryCollection and places them in a scrolling

 *  TextArea. The QueryCollection obtains the strings

 *  by means of a serialized object input stream

 *  connected to the QueryGenerator servlet.

 */

public class ShowQueries extends Applet

                         implements ActionListener, Runnable {

  private TextArea queryArea;

  private Button startButton, stopButton, clearButton;

  private QueryCollection currentQueries;

  private QueryCollection nextQueries;

  private boolean isRunning = false;

  private String address =

    "/servlet/coreservlets.QueryGenerator";

  private URL currentPage;

  public void init() {

    setBackground(Color.white);

    setLayout(new BorderLayout());

    queryArea = new TextArea();

    queryArea.setFont(new Font("Serif", Font.PLAIN, 14));

    add(queryArea, BorderLayout.CENTER);

    Panel buttonPanel = new Panel();

    Font buttonFont = new Font("SansSerif", Font.BOLD, 16);

    startButton = new Button("Start");

    startButton.setFont(buttonFont);

    startButton.addActionListener(this);

    buttonPanel.add(startButton);

    stopButton = new Button("Stop");

    stopButton.setFont(buttonFont);

    stopButton.addActionListener(this);

    buttonPanel.add(stopButton);

    clearButton = new Button("Clear TextArea");

Home page for this book: www.coreservlets.com; Home page for sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.