Custom tag question:

Jingh Yi

Ranch Hand

Posts: 90

posted 11 years ago

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 11 years ago

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 11 years ago

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 11 years ago

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 11 years ago

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 11 years ago

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 11 years ago

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 11 years ago

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

It is sorta covered in the JavaRanch Style Guide.

Custom tag question:

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