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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. It must not contain, for example, scriptlets or scriptlet expressions. At translation time, the container generates an implementation of the JspFragment interface 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. JSP fragments accept parameters from the invoker, which are exposed as Expression Language variables to the JSP code that composes the fragment. This allows the tag handler to parameterize the body each time it is invoked.
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.
Method Summary | |
void |
invoke(java.io.Writer out,
java.util.Map params)
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. |
Method Detail |
public void invoke(java.io.Writer out, java.util.Map params) throws JspException, java.io.IOException
out
- The Writer to output the fragment to, or null if
output should be sent to JspContext.getOut().params
- specifies the set of parameters to pass to the fragment.
Keys in this map are parameter names, and the
values are parameter values. This allows the invoker to
parameterize a fragment invocation.
JspException
- Thrown if an error occured
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.
java.io.IOException
- If there was an error writing to the
stream.
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