IfTag.java, IfConditionTag.java, IfThenTag.java, and IfElseTag.java, Custom tags that make use of tag nesting


IfTag.java

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** A tag that acts like an if/then/else.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfTag extends TagSupport {
  private boolean condition;
  private boolean hasCondition = false;

  public void setCondition(boolean condition) {
    this.condition = condition;
    hasCondition = true;
  }

  public boolean getCondition() {
    return(condition);
  }

  public void setHasCondition(boolean flag) {
    this.hasCondition = flag;
  }

  /** Has the condition field been explicitly set? */

  public boolean hasCondition() {
    return(hasCondition);
  }

  public int doStartTag() {
    return(EVAL_BODY_INCLUDE);
  }
}


package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The condition part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfConditionTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("condition not inside if");
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    String bodyString = getBodyContent().getString();
    if (bodyString.trim().equals("true")) {
      parent.setCondition(true);
    } else {
      parent.setCondition(false);
    }
    return(SKIP_BODY);
  }
}

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The else part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfElseTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("else not inside if");
    } else if (!parent.hasCondition()) {
      String warning =
        "condition tag must come before else tag";
      throw new JspTagException(warning);
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (!parent.getCondition()) {
      try {
        BodyContent body = getBodyContent();
        JspWriter out = body.getEnclosingWriter();
        out.print(body.getString());
      } catch(IOException ioe) {
        System.out.println("Error in IfElseTag: " + ioe);
      }
    }
    return(SKIP_BODY);
  }
}

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The then part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfThenTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("then not inside if");
    } else if (!parent.hasCondition()) {
      String warning =
        "condition tag must come before then tag";
      throw new JspTagException(warning);
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent.getCondition()) {
      try {
        BodyContent body = getBodyContent();
        JspWriter out = body.getEnclosingWriter();
        out.print(body.getString());
      } catch(IOException ioe) {
        System.out.println("Error in IfThenTag: " + ioe);
      }
    }
    return(SKIP_BODY);
  }
}

FilterExample.jsp Page that uses the FilterTag custom tag

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of FilterTag 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>HTML Logical Character Styles</TITLE>
<LINK REL=STYLESHEET
      HREF="JSP-Styles.css"
      TYPE="text/css">
</HEAD>
<BODY>
<H1>HTML Logical Character Styles</H1>
Physical character styles (B, I, etc.) are rendered consistently
in different browsers. Logical character styles, however,
may be rendered differently by different browsers.
Here's how your browser 
(<%= request.getHeader("User-Agent") %>) 
renders the HTML 4.0 logical character styles:
<P>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<TABLE BORDER=1 ALIGN="CENTER">
<TR CLASS="COLORED"><TH>Example<TH>Result
<TR>
<TD><PRE><cwp:filter>
<EM>Some emphasized text.</EM><BR>
<STRONG>Some strongly emphasized text.</STRONG><BR>
<CODE>Some code.</CODE><BR>
<SAMP>Some sample text.</SAMP><BR>
<KBD>Some keyboard text.</KBD><BR>
<DFN>A term being defined.</DFN><BR>
<VAR>A variable.</VAR><BR>
<CITE>A citation or reference.</CITE>
</cwp:filter></PRE>
<TD>
<EM>Some emphasized text.</EM><BR>
<STRONG>Some strongly emphasized text.</STRONG><BR>
<CODE>Some code.</CODE><BR>
<SAMP>Some sample text.</SAMP><BR>
<KBD>Some keyboard text.</KBD><BR>
<DFN>A term being defined.</DFN><BR>
<VAR>A variable.</VAR><BR>
<CITE>A citation or reference.</CITE>
</TABLE>
</BODY>
</HTML>


package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import cwp.*;

/** A tag that replaces <, >, ", and & with their HTML
 *  character entities (<, >, ", and &).
 *  After filtering, arbitrary strings can be placed
 *  in either the page body or in HTML attributes.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class FilterTag extends BodyTagSupport {
  public int doAfterBody() {
    BodyContent body = getBodyContent();
    String filteredBody =
      ServletUtilities.filter(body.getString());
    try {
      JspWriter out = body.getEnclosingWriter();
      out.print(filteredBody);
    } catch(IOException ioe) {
      System.out.println("Error in FilterTag: " + ioe);
    }
    // SKIP_BODY means we're done. If we wanted to evaluate
    // and handle the body again, we'd return EVAL_BODY_TAG.
    return(SKIP_BODY);
  }
}

^^^^^^^^^^^^^^^^^
TiledImages.java Demonstrates using a TexturePaint to fill an shape with a tiled image. Uses the following class and images:

    * ImageUtilities.java Simplifies creating a BufferedImage from an image file. 
~~~~~~~~~~~~~~~~~~
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;

/** An example of using TexturePaint to fill objects with tiled
 *  images. Uses the getBufferedImage method of ImageUtilities 
 *  to load an Image from a file and turn that into a 
 *  BufferedImage.
 *
 ****************

public class TiledImages extends JPanel {
  private String dir = System.getProperty("user.dir");
  private String imageFile1 = dir + "/images/marty.jpg";
  private TexturePaint imagePaint1;
  private Rectangle imageRect;
  private String imageFile2 = dir + "/images/bluedrop.gif";
  private TexturePaint imagePaint2;
  private int[] xPoints = { 30, 700, 400 };
  private int[] yPoints = { 30, 30, 600 };
  private Polygon imageTriangle =
                    new Polygon(xPoints, yPoints, 3);
  public TiledImages() {
    BufferedImage image =
      ImageUtilities.getBufferedImage(imageFile1, this);
    imageRect = new Rectangle(235, 70, image.getWidth(),
                              image.getHeight());
    imagePaint1 = new TexturePaint(image, imageRect);
    image = ImageUtilities.getBufferedImage(imageFile2, this);
    imagePaint2 =
      new TexturePaint(image, new Rectangle(0, 0, 32, 32));
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.setPaint(imagePaint2);
    g2d.fill(imageTriangle);
    g2d.setPaint(Color.blue);
    g2d.setStroke(new BasicStroke(5));
    g2d.draw(imageTriangle);
    g2d.setPaint(imagePaint1);
    g2d.fill(imageRect);
    g2d.setPaint(Color.black);
    g2d.draw(imageRect);
  }

  public static void main(String[] args) {
    WindowUtilities.openInJFrame(new TiledImages(), 750, 650);
  }
}
>>>>>>>>>>>>>>
ImageUtilities.java Simplifies creating a BufferedImage from an image file.
>>>>>>>>>>>>>>>
import java.awt.*;
import java.awt.image.*;

/** A class that simplifies a few common image operations, in
 *  particular, creating a BufferedImage from an image file and
 *  using MediaTracker to wait until an image or several images
 *  are done loading.
 *
 ********************

public class ImageUtilities {
  
  /** Create Image from a file, then turn that into a
   *  BufferedImage.
   */

  public static BufferedImage getBufferedImage(String imageFile,
                                               Component c) {
    Image image = c.getToolkit().getImage(imageFile);
    waitForImage(image, c);

    BufferedImage bufferedImage =
      new BufferedImage(image.getWidth(c), image.getHeight(c),
                        BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = bufferedImage.createGraphics();
    g2d.drawImage(image, 0, 0, c);
    return(bufferedImage);
  }

  /** Take an Image associated with a file, and wait until it is
   *  done loading (just a simple application of MediaTracker).
   *  If you are loading multiple images, don't use this
   *  consecutive times; instead, use the version that takes
   *  an array of images.
   */

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

  /** Take some Images associated with files, and wait until they
   *  are done loading (just a simple application of
   *  MediaTracker).
   */

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

import javax.swing.*;   // For JPanel, etc.
import java.awt.*;      // For Graphics, etc.
import java.awt.geom.*; // For Ellipse2D, etc.

/** An example of drawing/filling shapes with Java 2D in
 *  Java 1.2 and later.
 *
**************************
public class ShapeExample extends JPanel {
  private Ellipse2D.Double circle =
    new Ellipse2D.Double(10, 10, 350, 350);
  private Rectangle2D.Double square =
    new Rectangle2D.Double(10, 10, 350, 350);

  public void paintComponent(Graphics g) {
    clear(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.fill(circle);
    g2d.draw(square);
  }

  // super.paintComponent clears off screen pixmap,
  // since we're using double buffering by default.
  protected void clear(Graphics g) {
    super.paintComponent(g);
  }

  protected Ellipse2D.Double getCircle() {
    return(circle);
  }

public static void main(String[] args) {
    WindowUtilities.openInJFrame(new ShapeExample(), 380, 400);
  }
}

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

/** Lets the user enter the name of any
 *  good programming language. Or does it?
 *  


 *********************

public class JavaTextField extends Applet {
  public void init() {
    setFont(new Font("Serif", Font.BOLD, 14));
    setLayout(new GridLayout(2, 1));
    add(new Label("Enter a Good Programming Language",
                  Label.CENTER));
    LanguageField langField = new LanguageField();
    Font langFont = new Font("SansSerif", Font.BOLD, 18);
    langField.setFont(langFont);
    add(langField);
  }
}

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

/** Prints non-detailed reports of mouse events.
 *  Uses the low-level processXxxEvent methods instead
 *  of the usual event listeners.
 *  


 *****************

public class MouseReporter extends Applet {
  public void init() {
    setBackground(Color.blue); // So you can see applet in page
    enableEvents(AWTEvent.MOUSE_EVENT_MASK |
                 AWTEvent.MOUSE_MOTION_EVENT_MASK);
  }

  public void processMouseEvent(MouseEvent event) {
    System.out.println("Mouse enter/exit or click at (" +
                       event.getX() + "," +
                       event.getY() + ").");
    // In case there are MouseListeners attached:
    super.processMouseEvent(event); 
  }

  
  public void processMouseMotionEvent(MouseEvent event) {
    System.out.println("Mouse move/drag at (" +
                       event.getX() + "," +
                       event.getY() + ").");
    // In case there are MouseMotionListeners attached:
    super.processMouseMotionEvent(event);
  }
}

HeadingExample.jsp Page that uses the HeadingTag custom tag


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of HeadingTag 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>Some Tag-Generated Headings</TITLE>
</HEAD>
<BODY>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<cwp:heading bgColor="#C0C0C0">
Default Heading
</cwp:heading>
<P>
<cwp:heading bgColor="BLACK" color="WHITE">
White on Black Heading
</cwp:heading>
<P>
<cwp:heading bgColor="#EF8429" fontSize="60" border="5">
Large Bordered Heading
</cwp:heading>
<P>
<cwp:heading bgColor="CYAN" width="100%">
Heading with Full-Width Background
</cwp:heading>
<P>
<cwp:heading bgColor="CYAN" fontSize="60"
                fontList="Brush Script MT, Times, serif">
Heading with Non-Standard Font
</cwp:heading>
</BODY>
</HTML>

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;

/** Generates an HTML heading with the specified background
 *  color, foreground color, alignment, font, and font size.
 *  You can also turn on a border around it, which normally
 *  just barely encloses the heading, but which can also
 *  stretch wider. All attributes except the background
 *  color are optional.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class HeadingTag extends TagSupport {
  private String bgColor; // The one required attribute
  private String color = null;
  private String align="CENTER";
  private String fontSize="36";
  private String fontList="Arial, Helvetica, sans-serif";
  private String border="0";
  private String width=null;

  public void setBgColor(String bgColor) {
    this.bgColor = bgColor;
  }

  public void setColor(String color) {
    this.color = color;
  }

  public void setAlign(String align) {
    this.align = align;
  }

  public void setFontSize(String fontSize) {
    this.fontSize = fontSize;
  }

  public void setFontList(String fontList) {
    this.fontList = fontList;
  }

  public void setBorder(String border) {
    this.border = border;
  }

  public void setWidth(String width) {
    this.width = width;
  }

  public int doStartTag() {
    try {
      JspWriter out = pageContext.getOut();
      out.print("<TABLE BORDER=" + border +
                " BGCOLOR=\"" + bgColor + "\"" +
                " ALIGN=\"" + align + "\"");
      if (width != null) {
        out.print(" WIDTH=\"" + width + "\"");
      }
      out.print("><TR><TH>");
      out.print("<SPAN STYLE=\"" +
                "font-size: " + fontSize + "px; " +
                "font-family: " + fontList + "; ");
      if (color != null) {
        out.println("color: " + color + ";");
      }
      out.print("\"> "); // End of <SPAN ...>
    } catch(IOException ioe) {
      System.out.println("Error in HeadingTag: " + ioe);
    }
    return(EVAL_BODY_INCLUDE); // Include tag body
  }

  public int doEndTag() {
    try {
      JspWriter out = pageContext.getOut();
      out.print("</SPAN></TABLE>");
    } catch(IOException ioe) {
      System.out.println("Error in HeadingTag: " + ioe);
    }
    return(EVAL_PAGE); // Continue with rest of JSP page
  }
}

PrimeExample.jsp Page that uses the PrimeTag custom tag


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of PrimeTag 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>Some N-Digit Primes</TITLE>
<LINK REL=STYLESHEET
      HREF="JSP-Styles.css"
      TYPE="text/css">
</HEAD>
<BODY>
<H1>Some N-Digit Primes</H1>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<UL>
  <LI>20-digit: <cwp:prime length="20" />
  <LI>40-digit: <cwp:prime length="40" />
  <LI>80-digit: <cwp:prime length="80" />
  <LI>Default (50-digit): <cwp:prime />
</UL>
</BODY>
</HTML>



package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;

/** Generates an N-digit random prime (default N = 50).
 *  Extends SimplePrimeTag, adding a length attribute
 *  to set the size of the prime. The doStartTag
 *  method of the parent class uses the len field
 *  to determine the approximate length of the prime.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class PrimeTag extends SimplePrimeTag {
  public void setLength(String length) {
    try {
      len = Integer.parseInt(length);
    } catch(NumberFormatException nfe) {
      len = 50;
    }
  }
}

SimplePrimeExample.jsp Page that uses the SimplePrimeTag custom tag

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of SimplePrimeTag 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>Some 50-Digit Primes</TITLE>
<LINK REL=STYLESHEET
      HREF="JSP-Styles.css"
      TYPE="text/css">
</HEAD>
<BODY>
<H1>Some 50-Digit Primes</H1>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<UL>
  <LI><cwp:simplePrime />
  <LI><cwp:simplePrime />
  <LI><cwp:simplePrime />
  <LI><cwp:simplePrime />
</UL>
</BODY>
</HTML>

SimpleExample.jsp Page that uses the ExampleTag custom tag.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- 
Illustration of very simple JSP custom tag. 

Taken from Core Web Programming Java 2 Edition
from Prentice Hall and Sun Microsystems Press,
.
May be freely used or adapted. 
-->
<HTML>
<HEAD>
<%@ taglib uri="cwp-taglib.tld" prefix="cwp" %>
<TITLE><cwp:example /></TITLE>
<LINK REL=STYLESHEET
      HREF="JSP-Styles.css"
      TYPE="text/css">
</HEAD>
<BODY>
<H1><cwp:example /></H1>
<cwp:example />
</BODY>
</HTML>


ExampleTag

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;

/** Very simple JSP tag that just inserts a string
 *  ("Custom tag example...") into the output.
 *  The actual name of the tag is not defined here;
 *  that is given by the Tag Library Descriptor (TLD)
 *  file that is referenced by the taglib directive
 *  in the JSP file.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class ExampleTag extends TagSupport {
  public int doStartTag() {
    try {
      JspWriter out = pageContext.getOut();
      out.print("Custom tag example " +
                "(cwp.tags.ExampleTag)");
    } catch(IOException ioe) {
      System.out.println("Error in ExampleTag: " + ioe);
    }
    return(SKIP_BODY);
  }
}