Doubt in simple tag and classic tag access

[raja ram]

Hi,

I have following code

package com.scwcd;
 
import javax.servlet.jsp.tagext.*;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.SkipPageException;
public class TesTag extends SimpleTagSupport{
 
private String user;
 
public void setUser(String user){
  this.user=user;
}
 
public String getUser(){
 return user;
}
 
public void doTag() throws JspException,IOException{
   String []movie={"hi","this","is","Testing Chandras attribute"};
   getJspContext().getOut().println("hi this is from the CUSTOM testag  "+ user );
   getJspContext().getOut().println("Before throwing SkipPageException");
 
     getJspBody().invoke(null);
   TesTag  parent=(TesTag) getParent();
   while(parent != null){
     getJspContext().getOut().println("Inside The ParentTag ");
     parent=(TesTag)parent.getParent();
   }
 
}
 
 
 
}

and below code

package com.scwcd;
 
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.jsp.*;
 
public class Child extends TagSupport{
 
 
public int doStartTag() throws JspException{
 int i=0;
   try{
   pageContext.getOut().println("<p> getParent()  from Child");
   Tag parent= getParent();
   pageContext.getOut().println("<p> value of parent " + parent);
   while(parent != null){
      i++;
      pageContext.getOut().println("<p> getParent() ---->" + "i is " + i);
      parent=parent.getParent();
 
 
   }
   }catch(Exception e){e.printStackTrace(); }
 
  return EVAL_BODY_INCLUDE;
 
}
 
}
 

in my jsp when i say
<test:child>
<test:testing user="s_2">hi</test:testing>
</test:child>

this throws class cast exception but

<test:testing user="s_2">
<test:child/>
</test:testing>

works fine

here my child tag handler is Classic(Child) and testing tag handler is SimpleTag(TesTag).

when i have Classic tag inside Simple Tag it works but reverse will throw me class cast exception. I know that Simple tag can access Simple and classic tag and Classic tag can access only classic tag but i am not able to map it back with the code can any body explain me this?


Thanks
[ September 10, 2008: Message edited by: raja ram ]

[raja ram]

Hi,

Any updates on this.

Thanks

[raja ram]

Hi,

Can any body through some light on this so has to say what exactly is causing the class cast exception.

Thanks

[Sandeep Bhandari]

well the exact answer can be given by studying the implementation of TagSupport and SimpleTagSupport classes. But to give you a rough idea:

SimpleTagSupport is superset of TagSupport and hence can be the parent tag for classic tag.
But the reverse is not true and hence the issue yor are facing.

Will post more on this after doing a bit more research.

[Ranil Liyana Arachchige]

when you say getParent() in SimpleTagSupport it returns JspTag i guess, could you just have a look at that.

[Sandeep Bhandari]

yes, the culprit is setParent method

setParent() returns a JspTag object,
the returned parent tag can implement the Tag, BodyTag, IterationTag, or the
SimpleTag interface