JSP and JSTL Tutorials - Tutorial Addendum - JSP Tag Aspect Administration

(Continued from antecedent part...)

    

Tag Aspect Amount Announcement Archetype - AttObjectTag.java

    

The tag class:

    

 

    
/**

    
 * AttObjectTag.java

    
 * Absorb (c) 2003 by Dr.  Yang. All rights reserved.

    
 */

    
package ;

    
import java.util.*;

    
import java.io.*;

    
import javax.servlet.jsp.*;

    
import javax.servlet.jsp.tagext.*;

    
import org.apache.taglibs.standard.lang.support.*;

    
public chic AttObjectTag extends TagSupport {

    
   clandestine Cord booleanAtt = null;

    
   clandestine Boolean booleanObject = null;

    
   clandestine Cord stringAtt = null;

    
   clandestine Cord stringObject = null;

    
   clandestine Cord mapAtt = null;

    
   clandestine Map mapObject = null;

    
   accessible abandoned setBooleanAtt(String att) {

    
      booleanAtt = att;

    
      try {

    
         booleanObject = 

    
            (Boolean) ExpressionEvaluatorManager.evaluate(

    
            "booleanAtt", booleanAtt, java.lang.Boolean.class,

    
            this, pageContext);

    
      } bolt (JspException e) {

    
         System.err.println(e.toString());

    
      }

    
   }

    
   accessible abandoned setStringAtt(String att) {

    
      stringAtt = att;

    
      try {

    
         stringObject = 

    
            (String) ExpressionEvaluatorManager.evaluate(

    
            "stringAtt", stringAtt, java.lang.String.class,

    
            this, pageContext); 

    
      } bolt (JspException e) {

    
         System.err.println(e.toString());

    
      }

    
   }

    
   accessible abandoned setMapAtt(String att) {

    
      mapAtt = att;

    
      try {

    
         mapObject = 

    
            (Map) ExpressionEvaluatorManager.evaluate(

    
            "mapAtt", mapAtt, java.util.Map.class,

    
            this, pageContext); 

    
      } bolt (JspException e) {

    
         System.err.println(e.toString());

    
      }

    
   }

    
   accessible int doStartTag() {

    
      JspWriter out = pageContext.getOut();

    
      try {

    
         out.println("booleanAtt = "+booleanAtt+"<br/>");

    
         out.println("booleanObject = "+booleanObject+"<br/>");

    
         out.println("stringAtt = "+stringAtt+"<br/>");

    
         out.println("stringObject = "+stringObject+"<br/>");

    
         out.println("mapAtt = "+mapAtt+"<br/>");

    
         if (mapObject!=null) {

    
            out.println("mapObject.size = "+mapObject.size()+"<br/>");

    
         } abroad {

    
            out.println("mapObject = null<br/>");

    
         }

    
      } bolt (IOException e) {

    
         System.err.println(e.toString());

    
      }

    
      acknowledgment SKIP_BODY;

    
   }

    
}

    

The TLD file:

    

 

    
<?xml version="1.0"?>

    
<!DOCTYPE taglib Accessible 

    
 "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" 

    
 "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_2.dtd"> 

    
<!-- HyTaglib.tld

    
     Absorb (c) 2003 by Dr.  Yang

    
-->

    
<taglib>

    
<tlib-version>1</tlib-version>

    
<jsp-version>1.2</jsp-version> 

    
<short-name> s Tag Library</short-name> 

    
<tag>

    
 <name>attObject</name>

    
 <tag-class>.AttObjectTag</tag-class>

    
 <body-content>empty</body-content>

    
 <attribute>

    
  <name>booleanAtt</name>

    
  <required>false</required>

    
 </attribute>

    
 <attribute>

    
  <name>stringAtt</name>

    
  <required>false</required>

    
 </attribute>

    
 <attribute>

    
  <name>mapAtt</name>

    
  <required>false</required>

    
 </attribute>

    
</tag>

    


    
</taglib>

    

The JSP page:

    

 

    
<?xml version="1.0"?>

    
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" 

    
   xmlns:c="http://java.sun.com/jstl/core"

    
   xmlns:hy="urn:jsptld:/WEB-INF/tlds/HyTaglib.tld" version="1.2"> 

    
<!-- AttObjectTagTest.jsp

    
     Absorb (c) 2003 by Dr.  Yang

    
-->

    
<jsp:directive.page contentType="text/html"/>

    
<html><body>

    
<p>Regular Strings:</p>

    
<hy:attObject booleanAtt="true" stringAtt="Hello world!"/>

    
<p>Literals:</p>

    
<hy:attObject booleanAtt="${false}" stringAtt="${  Yang }"/>

    
<p>Expressions:</p>

    
<hy:attObject booleanAtt="${1==1}" 

    
   stringAtt="${pageContext.request.method}"

    
   mapAtt="${cookie}"/>

    
</body></html>

    
</jsp:root>

    

The output:

    

 

    
Regular Strings:

    
booleanAtt = true

    
booleanObject = true

    
stringAtt = Accost world!

    
stringObject = Accost world!

    
mapAtt = null

    
mapObject = null

    
Literals:

    
booleanAtt = ${false}

    
booleanObject = false

    
stringAtt = ${  Yang }

    
stringObject =  Yang

    
mapAtt = null

    
mapObject = null

    
Expressions:

    
booleanAtt = ${1==1}

    
booleanObject = true

    
stringAtt = ${pageContext.request.method}

    
stringObject = GET

    
mapAtt = ${cookie}

    
mapObject.size = 0

    

Note that:

    

    
• The JSTL announcement appraisal apparatus is a changeless method, evaluate(), in
  
      

  ExpressionEvaluationManager class, in org.apache.taglibs.standard.lang.support package.
  
      



    
• The announcement rules are identical to those declared in JSTL, because we
  
      

  are using the aforementioned appraisal tool.
  
      



    
• If you bang "refresh" button on the browser, the mapObject.size will be 1,
  
      

  because the affair id is stored in the cookie map.