~~~~~~~~~~~~~~~~~~~
ImageBox.java A class that incorrectly tries to load an image and draw an outline around it. The problem is that the size of the image is requested before the image is completely loaded, thus, returning a width and height of -1.
~~~~~~~~~~~~~~~~~~~
import java.applet.Applet;
import java.awt.*;

/** A class that incorrectly tries to load an image and draw an
 *  outline around it. Don't try this at home.
 *
 ********************

public class ImageBox extends Applet {
  private int imageWidth, imageHeight;
  private Image image;

  public void init() {
    String imageName = getParameter("IMAGE");
    if (imageName != null) {
      image = getImage(getDocumentBase(), imageName);
    } else {
      image = getImage(getDocumentBase(), "error.gif");
    }
    setBackground(Color.white);

    // The following is wrong, since the image won't be done
    // loading, and -1 will be returned.
    imageWidth = image.getWidth(this);
    imageHeight = image.getHeight(this);
  }

  public void paint(Graphics g) {
    g.drawImage(image, 0, 0, this);
    g.drawRect(0, 0, imageWidth, imageHeight);
  }
}
>>>>>>>>>>>>>>>>>>
BetterImageBox.java An improved version of ImageBox.java. Here a MediaTracker is used to block (wait till the image is completely loaded) before preceding to determine the image size.
>>>>>>>>>>>>>>>>>>
import java.applet.Applet;
import java.awt.*;

/** This version fixes the problems associated with ImageBox by
 *  using a MediaTracker to be sure the image is loaded before
 *  you try to get its dimensions.
 *
 *********************************

public class BetterImageBox extends Applet {
  private int imageWidth, imageHeight;
  private Image image;

  public void init() {
    String imageName = getParameter("IMAGE");
    if (imageName != null) {
      image = getImage(getDocumentBase(), imageName);
    } else {
      image = getImage(getDocumentBase(), "error.gif");
    }
    setBackground(Color.white);
    MediaTracker tracker = new MediaTracker(this);
    tracker.addImage(image, 0);
    try {
      tracker.waitForAll();
    } catch(InterruptedException ie) {}
    if (tracker.isErrorAny()) {
      System.out.println("Error while loading image");
    }

    // This is safe: image is fully loaded
    imageWidth = image.getWidth(this);
    imageHeight = image.getHeight(this);
  }

  public void paint(Graphics g) {
    g.drawImage(image, 0, 0, this);
    g.drawRect(0, 0, imageWidth, imageHeight);
  }
}
>>>>>>>>>>>>>>>>>
TrackerUtil.java A utility class that lets you load and wait for an image in a single swoop.
>>>>>>>>>>>>>>>>>
import java.awt.*;

/** A utility class that lets you load and wait for an image or
 *  images in one fell swoop. If you are loading multiple
 *  images, only use multiple calls to waitForImage if you
 *  need loading to be done serially. Otherwise, use
 *  waitForImages, which loads concurrently, which can be
 *  much faster.
 *
 *******************

public class TrackerUtil {
  public static boolean waitForImage(Image image, Component c) {
    MediaTracker tracker = new MediaTracker(c);
    tracker.addImage(image, 0);
    try {
      tracker.waitForAll();
    } catch(InterruptedException ie) {}
    if (tracker.isErrorAny()) {
      return(false);
    } else {
      return(true);
    }
  }

  public static boolean waitForImages(Image[] images,
                                      Component c) {
    MediaTracker tracker = new MediaTracker(c);
    for(int i=0; i>>>>>>>>>>>>>>>>>>>>>

HelloWWW2.java Illustrates the ability of an applet to read parameters contained in the HTML document (PARAM element containing a NAME-VALUE pair).

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
import java.applet.Applet;
import java.awt.*;

*************************

public class HelloWWW2 extends Applet {
  public void init() {
    setFont(new Font("SansSerif", Font.BOLD, 30));
    Color background = Color.gray;
    Color foreground = Color.darkGray;
    String backgroundType = getParameter("BACKGROUND");
    if (backgroundType != null) {
      if (backgroundType.equalsIgnoreCase("LIGHT")) {
        background = Color.white;
        foreground = Color.black;
      } else if (backgroundType.equalsIgnoreCase("DARK")) {
        background = Color.black;
        foreground = Color.white;
      }
    }
    setBackground(background);
    setForeground(foreground);
  }

  public void paint(Graphics g) {
    g.drawString("Hello, World Wide Web.", 5, 35);
  }
}
>>>>>>>>>>>>>>>>>>>>>>>

quick-search.html Front end to travel site

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!--
Front end to travel servlet.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Online Travel Quick Search</TITLE>
  <LINK REL=STYLESHEET
        HREF="travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<BR>
<H1>Online Travel Quick Search</H1>
<FORM ACTION="/servlet/cwp.Travel" METHOD="POST">
<CENTER>
Email address: <INPUT TYPE="TEXT" NAME="emailAddress"><BR>
Password: <INPUT TYPE="PASSWORD" NAME="password" SIZE=10><BR>
Origin: <INPUT TYPE="TEXT" NAME="origin"><BR>
Destination: <INPUT TYPE="TEXT" NAME="destination"><BR>
Start date (MM/DD/YY):
  <INPUT TYPE="TEXT" NAME="startDate" SIZE=8><BR>
End date (MM/DD/YY):
  <INPUT TYPE="TEXT" NAME="endDate" SIZE=8><BR>
<P>
<TABLE CELLSPACING=1>
<TR>
  <TH> <IMG SRC="airplane.gif" WIDTH=100 HEIGHT=29
                 ALIGN="TOP" ALT="Book Flight"> 
  <TH> <IMG SRC="car.gif" WIDTH=100 HEIGHT=31
                 ALIGN="MIDDLE" ALT="Rent Car"> 
  <TH> <IMG SRC="bed.gif" WIDTH=100 HEIGHT=85
                 ALIGN="MIDDLE" ALT="Find Hotel"> 
  <TH> <IMG SRC="passport.gif" WIDTH=71 HEIGHT=100
                 ALIGN="MIDDLE" ALT="Edit Account"> 
<TR>
  <TH><SMALL>
      <INPUT TYPE="SUBMIT" NAME="flights" VALUE="Book Flight">
      </SMALL>
  <TH><SMALL>
      <INPUT TYPE="SUBMIT" NAME="cars" VALUE="Rent Car">
      </SMALL>
  <TH><SMALL>
      <INPUT TYPE="SUBMIT" NAME="hotels" VALUE="Find Hotel">
      </SMALL>
  <TH><SMALL>
      <INPUT TYPE="SUBMIT" NAME="account" VALUE="Edit Account">
      </SMALL>
</TABLE>
</CENTER>
</FORM>
<BR>
<P ALIGN="CENTER">
<B>Not yet a member? Get a free account
<A HREF="accounts.jsp">here</A>.</B></P>
</BODY>
</HTML>


Travel.java  Servlet used by travel site. Uses the MVC architecture in that servlet just does computation; all presentation done by JSP. Uses the TravelCustomer bean.




package cwp;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

/** Top-level travel-processing servlet. This servlet sets up
 *  the customer data as a bean, then forwards the request
 *  to the airline booking page, the rental car reservation
 *  page, the hotel page, the existing account modification
 *  page, or the new account page.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class Travel extends HttpServlet {
  private TravelCustomer[] travelData;

  public void init() {
    travelData = TravelData.getTravelData();
  }

  /** Since password is being sent, use POST only. However,
   *  the use of POST means that you cannot forward
   *  the request to a static HTML page, since the forwarded
   *  request uses the same request method as the original
   *  one, and static pages cannot handle POST. Solution:
   *  have the "static" page be a JSP file that contains
   *  HTML only. That's what accounts.jsp is. The other
   *  JSP files really need to be dynamically generated,
   *  since they make use of the customer data.
   */

  public void doPost(HttpServletRequest request,
                     HttpServletResponse response)
      throws ServletException, IOException {
    String emailAddress = request.getParameter("emailAddress");
    String password = request.getParameter("password");
    TravelCustomer customer =
      TravelCustomer.findCustomer(emailAddress, travelData);
    if ((customer == null) || (password == null) ||
        (!password.equals(customer.getPassword()))) {
      gotoPage("/travel/accounts.jsp", request, response);
    }
    // The methods that use the following parameters will
    // check for missing or malformed values.
    customer.setStartDate(request.getParameter("startDate"));
    customer.setEndDate(request.getParameter("endDate"));
    customer.setOrigin(request.getParameter("origin"));
    customer.setDestination(request.getParameter
                              ("destination"));
    HttpSession session = request.getSession(true);
    session.setAttribute("customer", customer);
    if (request.getParameter("flights") != null) {
      gotoPage("/travel/BookFlights.jsp",
               request, response);
    } else if (request.getParameter("cars") != null) {
      gotoPage("/travel/RentCars.jsp",
               request, response);
    } else if (request.getParameter("hotels") != null) {
      gotoPage("/travel/FindHotels.jsp",
               request, response);
    } else if (request.getParameter("cars") != null) {
      gotoPage("/travel/EditAccounts.jsp",
               request, response);
    } else {
      gotoPage("/travel/IllegalRequest.jsp",
               request, response);
    }
  }

  private void gotoPage(String address,
                        HttpServletRequest request,
                        HttpServletResponse response)
      throws ServletException, IOException {
    RequestDispatcher dispatcher =
      getServletContext().getRequestDispatcher(address);
    dispatcher.forward(request, response);
  }
}






TravelCustomer Bean

package cwp;

import java.util.*;
import java.text.*;

/** Describes a travel services customer. Implemented
 *  as a bean with some methods that return data in HTML
 *  format, suitable for access from JSP.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class TravelCustomer {
  private String emailAddress, password, firstName, lastName;
  private String creditCardName, creditCardNumber;
  private String phoneNumber, homeAddress;
  private String startDate, endDate;
  private String origin, destination;
  private FrequentFlyerInfo[] frequentFlyerData;
  private RentalCarInfo[] rentalCarData;
  private HotelInfo[] hotelData;

  public TravelCustomer(String emailAddress,
                        String password,
                        String firstName,
                        String lastName,
                        String creditCardName,
                        String creditCardNumber,
                        String phoneNumber,
                        String homeAddress,
                        FrequentFlyerInfo[] frequentFlyerData,
                        RentalCarInfo[] rentalCarData,
                        HotelInfo[] hotelData) {
    setEmailAddress(emailAddress);
    setPassword(password);
    setFirstName(firstName);
    setLastName(lastName);
    setCreditCardName(creditCardName);
    setCreditCardNumber(creditCardNumber);
    setPhoneNumber(phoneNumber);
    setHomeAddress(homeAddress);
    setStartDate(startDate);
    setEndDate(endDate);
    setFrequentFlyerData(frequentFlyerData);
    setRentalCarData(rentalCarData);
    setHotelData(hotelData);
  }

  public String getEmailAddress() {
    return(emailAddress);
  }

  public void setEmailAddress(String emailAddress) {
    this.emailAddress = emailAddress;
  }

  public String getPassword() {
    return(password);
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public String getFirstName() {
    return(firstName);
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

  public String getLastName() {
    return(lastName);
  }

  public void setLastName(String lastName) {
    this.lastName = lastName;
  }

  public String getFullName() {
    return(getFirstName() + " " + getLastName());
  }

  public String getCreditCardName() {
    return(creditCardName);
  }

  public void setCreditCardName(String creditCardName) {
    this.creditCardName = creditCardName;
  }

  public String getCreditCardNumber() {
    return(creditCardNumber);
  }

  public void setCreditCardNumber(String creditCardNumber) {
    this.creditCardNumber = creditCardNumber;
  }

  public String getCreditCard() {
    String cardName = getCreditCardName();
    String cardNum = getCreditCardNumber();
    cardNum = cardNum.substring(cardNum.length() - 4);
    return(cardName + " (XXXX-XXXX-XXXX-" + cardNum + ")");
  }

  public String getPhoneNumber() {
    return(phoneNumber);
  }

  public void setPhoneNumber(String phoneNumber) {
    this.phoneNumber = phoneNumber;
  }

  public String getHomeAddress() {
    return(homeAddress);
  }

  public void setHomeAddress(String homeAddress) {
    this.homeAddress = homeAddress;
  }

  public String getStartDate() {
    return(startDate);
  }

  public void setStartDate(String startDate) {
    this.startDate = startDate;
  }

  public String getEndDate() {
    return(endDate);
  }

  public void setEndDate(String endDate) {
    this.endDate = endDate;
  }

  public String getOrigin() {
    return(origin);
  }

  public void setOrigin(String origin) {
    this.origin = origin;
  }

  public String getDestination() {
    return(destination);
  }

  public void setDestination(String destination) {
    this.destination = destination;
  }

  public FrequentFlyerInfo[] getFrequentFlyerData() {
    return(frequentFlyerData);
  }

  public void setFrequentFlyerData(FrequentFlyerInfo[]
                                   frequentFlyerData) {
    this.frequentFlyerData = frequentFlyerData;
  }

  public String getFrequentFlyerTable() {
    FrequentFlyerInfo[] frequentFlyerData =
      getFrequentFlyerData();
    if (frequentFlyerData.length == 0) {
      return("<I>No frequent flyer data recorded.</I>");
    } else {
      String table =
        "<TABLE>\n" +
        "  <TR><TH>Airline<TH>Frequent Flyer Number\n";
      for(int i=0; i<frequentFlyerData.length; i++) {
        FrequentFlyerInfo info = frequentFlyerData[i];
        table = table +
                "<TR ALIGN=\"CENTER\">" +
                "<TD>" + info.getAirlineName() +
                "<TD>" + info.getFrequentFlyerNumber() + "\n";
      }
      table = table + "</TABLE>\n";
      return(table);
    }
  }

  public RentalCarInfo[] getRentalCarData() {
    return(rentalCarData);
  }

  public void setRentalCarData(RentalCarInfo[] rentalCarData) {
    this.rentalCarData = rentalCarData;
  }

  public HotelInfo[] getHotelData() {
    return(hotelData);
  }

  public void setHotelData(HotelInfo[] hotelData) {
    this.hotelData = hotelData;
  }

  // This would be replaced by a database lookup
  // in a real application.

  public String getFlights() {
    String flightOrigin =
      replaceIfMissing(getOrigin(), "Nowhere");
    String flightDestination =
      replaceIfMissing(getDestination(), "Nowhere");
    Date today = new Date();
    DateFormat formatter =
      DateFormat.getDateInstance(DateFormat.MEDIUM);
    String dateString = formatter.format(today);
    String flightStartDate =
      replaceIfMissing(getStartDate(), dateString);
    String flightEndDate =
      replaceIfMissing(getEndDate(), dateString);
    String [][] flights =
      { { "Java Airways", "1522", "455.95", "Java, Indonesia",
          "Sun Microsystems", "9:00", "3:15" },
        { "Servlet Express", "2622", "505.95", "New Atlanta",
          "New Atlanta", "9:30", "4:15" },
        { "Geek Airlines", "3.14159", "675.00", "JHU",
          "MIT", "10:02:37", "2:22:19" } };
    String flightString = "";
    for(int i=0; i<flights.length; i++) {
      String[] flightInfo = flights[i];
      flightString =
        flightString + getFlightDescription(flightInfo[0],
                                            flightInfo[1],
                                            flightInfo[2],
                                            flightInfo[3],
                                            flightInfo[4],
                                            flightInfo[5],
                                            flightInfo[6],
                                            flightOrigin,
                                            flightDestination,
                                            flightStartDate,
                                            flightEndDate);
    }
    return(flightString);
  }

  private String getFlightDescription(String airline,
                                      String flightNum,
                                      String price,
                                      String stop1,
                                      String stop2,
                                      String time1,
                                      String time2,
                                      String flightOrigin,
                                      String flightDestination,
                                      String flightStartDate,
                                      String flightEndDate) {
    String flight =
      "<P><BR>\n" +
      "<TABLE WIDTH=\"100%\"><TR><TH CLASS=\"COLORED\">\n" +
      "<B>" + airline + " Flight " + flightNum +
      " ($" + price + ")</B></TABLE><BR>\n" +
      "<B>Outgoing:</B> Leaves " + flightOrigin +
      " at " + time1 + " AM on " + flightStartDate +
      ", arriving in " + flightDestination +
      " at " + time2 + " PM (1 stop -- " + stop1 + ").\n" +
      "<BR>\n" +
      "<B>Return:</B> Leaves " + flightDestination +
      " at " + time1 + " AM on " + flightEndDate +
      ", arriving in " + flightOrigin +
      " at " + time2 + " PM (1 stop -- " + stop2 + ").\n";
    return(flight);
  }

  private String replaceIfMissing(String value,
                                  String defaultValue) {
    if ((value != null) && (value.length() > 0)) {
      return(value);
    } else {
      return(defaultValue);
    }
  }

  public static TravelCustomer findCustomer
                                 (String emailAddress,
                                  TravelCustomer[] customers) {
    if (emailAddress == null) {
      return(null);
    }
    for(int i=0; i<customers.length; i++) {
      String custEmail = customers[i].getEmailAddress();
      if (emailAddress.equalsIgnoreCase(custEmail)) {
        return(customers[i]);
      }
    }
    return(null);
  }
}



BookFlights.jsp, RentCars.jsp, FindHotels.jsp, EditAccounts.jsp, and IllegalRequest.jsp Pages used by the Travel servlet to do its presentation.


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Flight-finding page for travel example.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Best Available Flights</TITLE>
  <LINK REL=STYLESHEET
        HREF="/travel/travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<H1>Best Available Flights</H1>
<CENTER>
<jsp:useBean id="customer"
             class="cwp.TravelCustomer" 
             scope="session" />
Finding flights for
<jsp:getProperty name="customer" property="fullName" />
<P>
<jsp:getProperty name="customer" property="flights" />
<P><BR><HR><BR>
<FORM ACTION="/servlet/BookFlight">
<jsp:getProperty name="customer" 
                 property="frequentFlyerTable" />
<P>
<B>Credit Card:</B>
<jsp:getProperty name="customer" property="creditCard" />
<P>
<INPUT TYPE="SUBMIT" NAME="holdButton" VALUE="Hold for 24 Hrs">
<P>
<INPUT TYPE="SUBMIT" NAME="bookItButton" VALUE="Book It!">
</FORM>
</CENTER>
</BODY>
</HTML>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Car rental page not implemented -- see airline booking page.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Not Implemented</TITLE>
  <LINK REL=STYLESHEET
        HREF="/travel/travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<H1>Car Rental Page Not Implemented</H1>
<CENTER>
Hey, this is only an example. See the airline booking page.
</CENTER>
</BODY>
</HTML>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Hotel page not implemented -- see airline booking page.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Not Implemented</TITLE>
  <LINK REL=STYLESHEET
        HREF="/travel/travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<H1>Hotel Page Not Implemented</H1>
<CENTER>
Hey, this is only an example. See the airline booking page.
</CENTER>
</BODY>
</HTML>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Account page not implemented -- see airline booking page.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Not Implemented</TITLE>
  <LINK REL=STYLESHEET
        HREF="/travel/travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<H1>Accounts Page Not Implemented</H1>
<CENTER>
Hey, this is only an example. See the airline booking page.
</CENTER>
</BODY>
</HTML>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illegal request at Travel Quick Search page.

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted.
-->
<HTML>
<HEAD>
  <TITLE>Illegal Request</TITLE>
  <LINK REL=STYLESHEET
        HREF="/travel/travel-styles.css"
        TYPE="text/css">
</HEAD>
<BODY>
<H1>Illegal Request</H1>
<CENTER>Please try again.</CENTER>
</BODY>
</HTML>

IfExample.jsp Page that uses the custom nested tags


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of IfTag tag. 

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted. 
-->
<HTML>
<HEAD>
<TITLE>If Tag Example</TITLE>
<LINK REL=STYLESHEET
      HREF="JSP-Styles.css"
      TYPE="text/css">
</HEAD>
<BODY>
<H1>If Tag Example</H1>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<cwp:if>
  <cwp:condition>true</cwp:condition>
  <cwp:then>Condition is true</cwp:then>
  <cwp:else>Condition is false</cwp:else>
</cwp:if>
<P>
<cwp:if>
  <cwp:condition><%= request.isSecure() %></cwp:condition>
  <cwp:then>Request is using SSL (https)</cwp:then>
  <cwp:else>Request is not using SSL</cwp:else>
</cwp:if>
<P>
Some coin tosses:<BR>
<cwp:repeat reps="10">
  <cwp:if>
    <cwp:condition><%= Math.random() < 0.5 %></cwp:condition>
    <cwp:then><B>Heads</B><BR></cwp:then>
    <cwp:else><B>Tails</B><BR></cwp:else>
  </cwp:if>
</cwp:repeat>
</BODY>
</HTML>

*/

public class Statics {
 public static void main(String[] args) {
    staticMethod();
    Statics s1 = new Statics();
    s1.regularMethod();
  }

  public static void staticMethod() {
    System.out.println("This is a static method.");
  }

  public void regularMethod() {
    System.out.println("This is a regular method.");
  }
}

import java.applet.Applet;
import java.awt.*;

/././././././

public class Buttons extends Applet {
  private Button button1, button2, button3;
  
  public void init() {
    button1 = new Button("Button One");
    button2 = new Button("Button Two");
    button3 = new Button("Button Three");
    add(button1);
    add(button2);
    add(button3);
  }
}
/././././././././.