requestdispatcher.java

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/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written 
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache"
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * ====================================================================
 *
 * This source code implements specifications defined by the Java
 * Community Process. In order to remain compliant with the specification
 * DO NOT add / change / or delete method signatures!
 */ 


package javax.servlet;

import java.io.IOException;


/**
 * Defines an object that receives requests from the client
 * and sends them to any resource (such as a servlet, 
 * HTML file, or JSP file) on the server. The servlet
 * container creates the <code>RequestDispatcher</code> object,
 * which is used as a wrapper around a server resource located
 * at a particular path or given by a particular name.
 *
 * <p>This interface is intended to wrap servlets,
 * but a servlet container can create <code>RequestDispatcher</code>
 * objects to wrap any type of resource.
 *
 * @author 	Various
 * @version 	$Version$
 *
 * @see 	ServletContext#getRequestDispatcher(java.lang.String)
 * @see 	ServletContext#getNamedDispatcher(java.lang.String)
 * @see 	ServletRequest#getRequestDispatcher(java.lang.String)
 *
 */
 
public interface RequestDispatcher {





/**
 * Forwards a request from
 * a servlet to another resource (servlet, JSP file, or
 * HTML file) on the server. This method allows
 * one servlet to do preliminary processing of
 * a request and another resource to generate
 * the response.
 *
 * <p>For a <code>RequestDispatcher</code> obtained via 
 * <code>getRequestDispatcher()</code>, the <code>ServletRequest</code> 
 * object has its path elements and parameters adjusted to match
 * the path of the target resource.
 *
 * <p><code>forward</code> should be called before the response has been 
 * committed to the client (before response body output has been flushed).  
 * If the response already has been committed, this method throws
 * an <code>IllegalStateException</code>.
 * Uncommitted output in the response buffer is automatically cleared 
 * before the forward.
 *
 * <p>The request and response parameters must be the same
 * objects as were passed to the calling servlet's service method.
 *
 *
 * @param request		a {@link ServletRequest} object
 *				that represents the request the client
 * 				makes of the servlet
 *
 * @param response		a {@link ServletResponse} object
 *				that represents the response the servlet
 *				returns to the client
 *
 * @exception ServletException	if the target resource throws this exception
 *
 * @exception IOException	if the target resource throws this exception
 *
 * @exception IllegalStateException	if the response was already committed
 *
 */

    public void forward(ServletRequest request, ServletResponse response)
	throws ServletException, IOException;




    /**
     *
     * Includes the content of a resource (servlet, JSP page,
     * HTML file) in the response. In essence, this method enables 
     * programmatic server-side includes.
     *
     * <p>The {@link ServletResponse} object has its path elements
     * and parameters remain unchanged from the caller's. The included
     * servlet cannot change the response status code or set headers;
     * any attempt to make a change is ignored.
     *
     * <p>The request and response parameters must be the same
     * objects as were passed to the calling servlet's service method.
     *
     *
     * @param request 			a {@link ServletRequest} object 
     *					that contains the client's request
     *
     * @param response 			a {@link ServletResponse} object 
     * 					that contains the servlet's response
     *
     * @exception ServletException 	if the included resource throws this exception
     *
     * @exception IOException 		if the included resource throws this exception
     *
     *
     */
     
    public void include(ServletRequest request, ServletResponse response)
	throws ServletException, IOException;
}