Tags with Bodies

<< Classic Tag Handler | Tag Handler Manipulates the Body >>

Tags with Bodies

The JSP page's servlet invokes the setPageContext, setParent, and attribute-setting methods
before calling doStartTag. The JSP page's servlet also guarantees that release will be invoked
on the tag handler before the end of the page.

Here is a typical tag handler method invocation sequence:

ATag t = new ATag();

t.setPageContext(...);

t.setParent(...);

t.setAttribute1(value1);

t.setAttribute2(value2);

t.doStartTag();

t.doEndTag();

t.release();

The BodyTag interface extends Tag by defining additional methods that let a tag handler access
its body. The interface provides three new methods:

setBodyContent

: Creates body content and adds to the tag handler

doInitBody

: Called before evaluation of the tag body

doAfterBody

: Called after evaluation of the tag body

A typical invocation sequence is as follows:

t.doStartTag();

out = pageContext.pushBody();

t.setBodyContent(out);

// perform any initialization needed after body content is set

t.doInitBody();

t.doAfterBody();

// while doAfterBody

returns EVAL_BODY_AGAIN

// iterate body evaluation

...

t.doAfterBody();

t.doEndTag();

out = pageContext.popBody();

t.release();

Tags with Bodies

A tag handler for a tag with a body is implemented differently depending on whether or not the
tag handler needs to manipulate the body. A tag handler manipulates the body when it reads or
modifies the contents of the body.

Programming Tags That Accept Scripting Elements

The Java EE 5 Tutorial · September 2007

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