Forum:

Web Component Certification (OCEJWCD)

Custom tag question:

Ranch Hand

Posts: 90

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

My tag handler class:

package com.example;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
 
public class Hello extends BodyTagSupport {
private String name=null;
    private int iterations=1;
 
/**
     * Getter/Setter for the attribute name as defined in the tld file 
     * for this tag
     */
public void setName(String value){
name = value;
}
 
public String getName(){
return(name);
}
/**
     * Getter/Setter for the attribute iterations as defined in the tld file 
     * for this tag
     */
 
public void setIterations(String value){
     try {
       iterations = Integer.parseInt(value);
     } catch(NumberFormatException nfe) {
       iterations = 1;
     }
   }
 
public String getIterations(){
return(Integer.toString(iterations));
}
 
    public int doStartTag() throws JspTagException{
  try {
        JspWriter out = pageContext.getOut();
        out.println("<table border=\"1\">");
     if (name != null)
      out.println("<tr><td> Hello " + name + " </td></tr>");
        else
      out.println("<tr><td> Hello World <td></tr>");
  } catch (Exception ex) {
    throw new JspTagException("All is not well in the world." + ex );
  }
  // Evaluate the body if there is one
  return EVAL_BODY_INCLUDE;
    }
 
public int doEndTag()throws JspTagException {
   try {
        JspWriter out = pageContext.getOut();
        out.println("</table>");
   } catch (Exception ex){
    throw new JspTagException("All is not well in the world." + ex);
   }
   return EVAL_PAGE;
}
 
public int doAfterBody() throws JspTagException {
    if (iterations-- >= 1) {
      BodyContent body = getBodyContent();
      try {
// Make sure we put anything in the output stream in the 
// body to the output stream of the JSP
        JspWriter out = body.getEnclosingWriter();
        out.println(body.getString());
body.clearBody(); // Clear for next evaluation
      } catch(IOException ioe) {
        throw new JspTagException("Error in Hello tag doAfterBody " + ioe);
            }
            return(EVAL_BODY_AGAIN);
      } else {
      return(SKIP_BODY); 
      }
    }
 
}

My view.jsp:

My TLD:

My question:
How come in doAfterBody(), second line, getBodyContent() returns null?

Thanks!
Jenny

Osama Hasan

Ranch Hand

Posts: 53

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi Jenny!
You should return EVAL_BODY_BUFFERED instead of EVAL_BODY_INCLUDE.
Hope it helps.

SCJP 1.4<br />SCWCD 1.4

Jingh Yi

Ranch Hand

Posts: 90

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi Osama! It's so cool. It worked after I did what you said.

But... I'm confused... when doStartTag() returns EVAL_BODY_INCLUDE, doesn't the control go to evaluate body? why do I have to have EVAL_BODY_BUFFERED? I don't have setBodyContent() or doInitBody() defined.

Thanks!
Jenny

Osama Hasan

Ranch Hand

Posts: 53

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi Jenny!
BodyContent is available only when the body is buffered. Thus, when we return EVAL_BODY_INCLUDE from doStartTag() the body is not buffered and hence BodyContent is not available.

SCJP 1.4<br />SCWCD 1.4

Jingh Yi

Ranch Hand

Posts: 90

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Oh thanks, Osama! I didn't know that.

BTW, can I implement the body iteration by using TagSupport?

Osama Hasan

Ranch Hand

Posts: 53

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

The TagSupport class implements the IterationTag interface. So, you certainly can.

SCJP 1.4<br />SCWCD 1.4

Jingh Yi

Ranch Hand

Posts: 90

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Osama,

I tried to extend TagSupport, but couldn't compile. getBodyContent() is not recognized. How do I get body content then?

Thanks!
Jenny

kapil munjal

Ranch Hand

Posts: 298

posted 18 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Try to find out...if getBodyContent() method belongs to BodyTagSupport class.

That can be the only reason.

Kapil Munjal
SCJP 1.4, SCWCD 1.4