Tomcat example source code file (JspFragment.java)

This example Tomcat source code file (JspFragment.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

http, io, ioexception, ioexception, jspcontext, jspcontext, jspexception, jspfragment, jspfragment, servlet, writer, writer

The Tomcat JspFragment.java source code

/*
* 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.*;

/**
 * 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.
 * <p>
 * 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.
 * <p>
 * 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.
 * <p>
 * Note that tag library developers and page authors should not generate
 * JspFragment implementations manually.
 * <p>
 * <i>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 occured
     *     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();

}