BodyTagSupport return values

[Kathiresan Chinna]

Hi All,

Actually I need to do something in doInitBody() method,
also the body content must be evaluated. So, I use BodyTagSupport.

1. I have a custom tag declared as

   <tag>
<description>Body Tag1</description>
<name>bodytag1</name>
<tag-class>com.web.classictag.BodyTag1Handler</tag-class>
        <body-content>scriptless</body-content>
   </tag>
  

2. The class BodyTag1Handler extends BodyTagSupport.

3. In JSP

  <ck:bodytag1>
    Hai ${requestScope.HandlerMsg} <br>
  </ck:bodytag1>
 

This is what happening:

1. If doStartTag() return EVAL_BODY_INCLUDE

Body is Evaluated and doAfterBody() is called.
setBodyContent() and doInitBody() is Not called.

This is OK

2. If doStartTag() return EVAL_BODY_BUFFERED

Body is Not Evaluated and doAfterBody() is Not called
But, setBodyContent() and doInitBody() is called.


The Lifecycle described in HFSJ page 563 is not happening in the case 2.

Can someone please tell am I missing anything ?

Thanks in advance
Kathir

[Kathiresan Chinna]

[Christophe Verré]

I don't have the book, so I don't know what the figure looks like. But I'm surprised that doAfterBody() is not called. Really ? Can you show what your tag handler looks like ?

[Kathiresan Chinna]

Hi Christophe,

Here is the class

  
 
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;
 
public class BodyTag1Handler extends BodyTagSupport
{

 
@Override
public int doStartTag() throws JspException
{
JspWriter out = pageContext.getOut();

pageContext.getRequest().setAttribute("HandlerMsg", "This was set in Handler");
 
try
{
out.println("  doStartTag() - from BodyTag1Handler  <br> ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}
  
//return EVAL_BODY_INCLUDE;


return EVAL_BODY_BUFFERED;
}

@Override
public void doInitBody() throws JspException
{
JspWriter out = pageContext.getOut();

try
{
out.println(" doInitBody() -  from BodyTag1Handler  <br>  ");
System.out.println(" doInitBody() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}

 }

@Override
public void setBodyContent(BodyContent content) 
{
JspWriter out = pageContext.getOut();

try
{
out.println(" setBodyContent() -  from BodyTag1Handler  <br>  ");
System.out.println(" setBodyContent() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
//throw new JspException("IOException- " + ex.toString());
}

 }

@Override
public int doAfterBody() throws JspException
{

JspWriter out = pageContext.getOut();

try
{
out.println(" doAfterBody() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}
 
 
return SKIP_BODY;

}
 
@Override
public int doEndTag() throws JspException
{
JspWriter out = pageContext.getOut();

try
{
out.println("  doEndTag() - from BodyTag1Handler  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}


return EVAL_PAGE;
}
 
}
  

[Christophe Verré]

You're falling into two common pitfalls :

1. You are overriding setBodyContent without setting the BodyContent anywhere. You need to at least call super.setBodyContent, or save the BodyContent into an instance variable. (If you don't use the BodyContent, it's not a problem)

2. The "page context's "out" is being pushed before doAfterBody is called. So when you use JspWriter out = pageContext.getOut();, you are not accessing the page's output stream, but the body buffer stream. That's why nothing is output to your client. You need to either output the body to the original "out", or get it directly with :

BodyContent body = super.getBodyContent();
JspWriter out = body.getEnclosingWriter();

Here is a new version of your tag :

import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;
 
public class BodyTagHandler extends BodyTagSupport
{
 
@Override
public int doStartTag() throws JspException
{
JspWriter out = pageContext.getOut();

pageContext.getRequest().setAttribute("HandlerMsg", "This was set in Handler");
 
try
{
out.println("  doStartTag() - from BodyTag1Handler  <br> ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}
  
//return EVAL_BODY_INCLUDE;


return EVAL_BODY_BUFFERED;
}

@Override
public void doInitBody() throws JspException
{
//JspWriter out = pageContext.getOut();
BodyContent body = super.getBodyContent();
JspWriter out = body.getEnclosingWriter();
 

try
{
out.println(" doInitBody() -  from BodyTag1Handler  <br>  ");
System.out.println(" doInitBody() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}

 }

@Override
public void setBodyContent(BodyContent content) 
{
super.setBodyContent(content);
JspWriter out = pageContext.getOut();

try
{
out.println(" setBodyContent() -  from BodyTag1Handler  <br>  ");
System.out.println(" setBodyContent() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
//throw new JspException("IOException- " + ex.toString());
}

 }

@Override
public int doAfterBody() throws JspException
{

//JspWriter out = pageContext.getOut();
BodyContent body = super.getBodyContent();
JspWriter out = body.getEnclosingWriter();

try
{
out.println(" doAfterBody() -  from BodyTag1Handler  <br>  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}
 
 
return SKIP_BODY;

}
 
@Override
public int doEndTag() throws JspException
{
JspWriter out = pageContext.getOut();

try
{
out.println("  doEndTag() - from BodyTag1Handler  ");
}
catch( IOException ex)
{
throw new JspException("IOException- " + ex.toString());
}


return EVAL_PAGE;
}
 
}

[ December 25, 2008: Message edited by: Christophe Verre ]

[Kathiresan Chinna]

aha.. Working fine.

Thank you Christophe
Kathir