javax.servlet.jsp.tagext

Class JspFragment

java.lang.Object

javax.servlet.jsp.tagext.JspFragment

Direct Known Subclasses:

JspFragmentHelper

public abstract class JspFragment
extends Object

Encapsulates a portion of JSP code in an object that can be invoked as many times as needed. JSP Fragments are defined using JSP syntax as the body of a tag for an invocation to a SimpleTag handler, or as the body of a <jsp:attribute> standard action specifying the value of an attribute that is declared as a fragment, or to be of type JspFragment in the TLD.

The definition of the JSP fragment must only contain template text and JSP action elements. In other words, it must not contain scriptlets or scriptlet expressions. At translation time, the container generates an implementation of the JspFragment abstract class capable of executing the defined fragment.

A tag handler can invoke the fragment zero or more times, or pass it along to other tags, before returning. To communicate values to/from a JSP fragment, tag handlers store/retrieve values in the JspContext associated with the fragment.

Note that tag library developers and page authors should not generate JspFragment implementations manually.

Implementation Note: It is not necessary to generate a separate class for each fragment. One possible implementation is to generate a single helper class for each page that implements JspFragment. Upon construction, a discriminator can be passed to select which fragment that instance will execute.

Since:

2.0

Constructor Summary

Constructors

Constructor and Description
JspFragment()

Method Summary

Modifier and Type	Method and Description
abstract JspContext	getJspContext() Returns the JspContext that is bound to this JspFragment.
abstract void	invoke(Writer out) Executes the fragment and directs all output to the given Writer, or the JspWriter returned by the getOut() method of the JspContext associated with the fragment if out is null.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JspFragment

public JspFragment()

Method Detail

invoke

public abstract void invoke(Writer out)
                     throws JspException,
                            IOException

Executes the fragment and directs all output to the given Writer, or the JspWriter returned by the getOut() method of the JspContext associated with the fragment if out is null.

Parameters:

out - The Writer to output the fragment to, or null if output should be sent to JspContext.getOut().

Throws:

JspException - Thrown if an error occurred while invoking this fragment.

SkipPageException - Thrown if the page that (either directly or indirectly) invoked the tag handler that invoked this fragment is to cease evaluation. The container must throw this exception if a Classic Tag Handler returned Tag.SKIP_PAGE or if a Simple Tag Handler threw SkipPageException.

IOException - If there was an error writing to the stream.

getJspContext

public abstract JspContext getJspContext()

Returns the JspContext that is bound to this JspFragment.

Returns:

The JspContext used by this fragment at invocation time.