javax.servlet.jsp.tagext.JspFragment Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp.tagext;
import java.io.IOException;
import java.io.Writer;
import javax.servlet.jsp.JspContext;
import javax.servlet.jsp.JspException;
/**
* 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
*/
public abstract class JspFragment {
/**
* 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.
*
* @param out The Writer to output the fragment to, or null if
* output should be sent to JspContext.getOut().
* @throws javax.servlet.jsp.JspException Thrown if an error occurred
* while invoking this fragment.
* @throws javax.servlet.jsp.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.
* @throws java.io.IOException If there was an error writing to the
* stream.
*/
public abstract void invoke( Writer out )
throws JspException, IOException;
/**
* Returns the JspContext that is bound to this JspFragment.
*
* @return The JspContext used by this fragment at invocation time.
*/
public abstract JspContext getJspContext();
}