trunk/core/src/main/java/org/apache/struts2/dispatcher/ServletDispatcherResult.java

/*
 * $Id$
 *
 * Copyright 2006 The Apache Software Foundation.
 *
 * Licensed 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 org.apache.struts2.dispatcher;

import javax.servlet.RequestDispatcher;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.PageContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionInvocation;


/**
 * <!-- START SNIPPET: description -->
 *
 * Includes or forwards to a view (usually a jsp). Behind the scenes Struts
 * will use a RequestDispatcher, where the target servlet/JSP receives the same
 * request/response objects as the original servlet/JSP. Therefore, you can pass
 * data between them using request.setAttribute() - the Struts action is
 * available.
 * <p/>
 * There are three possible ways the result can be executed:
 *  
 * <ul>
 *
 * <li>If we are in the scope of a JSP (a PageContext is available), PageContext's
 * {@link PageContext#include(String) include} method is called.</li>
 *
 * <li>If there is no PageContext and we're not in any sort of include (there is no
 * "javax.servlet.include.servlet_path" in the request attributes), then a call to
 * {@link RequestDispatcher#forward(javax.servlet.ServletRequest, javax.servlet.ServletResponse) forward}
 * is made.</li>
 * 
 * <li>Otherwise, {@link RequestDispatcher#include(javax.servlet.ServletRequest, javax.servlet.ServletResponse) include}
 * is called.</li>
 * 
 * </ul>
 * <!-- END SNIPPET: description -->
 *
 * <b>This result type takes the following parameters:</b>
 *
 * <!-- START SNIPPET: params -->
 *
 * <ul>
 *
 * <li><b>location (default)</b> - the location to go to after execution (ex. jsp).</li>
 *
 * <li><b>parse</b> - true by default. If set to false, the location param will not be parsed for Ognl expressions.</li>
 *
 * </ul>
 *
 * <!-- END SNIPPET: params -->
 *
 * <b>Example:</b>
 *
 * <pre><!-- START SNIPPET: example -->
 * &lt;result name="success" type="dispatcher"&gt;
 *   &lt;param name="location"&gt;foo.jsp&lt;/param&gt;
 * &lt;/result&gt;
 * <!-- END SNIPPET: example --></pre>
 *
 * This result follows the same rules from {@link StrutsResultSupport}.
 *
 * @see javax.servlet.RequestDispatcher
 */
public class ServletDispatcherResult extends StrutsResultSupport {

	private static final long serialVersionUID = -1970659272360685627L;
	
	private static final Log log = LogFactory.getLog(ServletDispatcherResult.class);


    /**
     * Dispatches to the given location. Does its forward via a RequestDispatcher. If the
     * dispatch fails a 404 error will be sent back in the http response.
     *
     * @param finalLocation the location to dispatch to.
     * @param invocation    the execution state of the action
     * @throws Exception if an error occurs. If the dispatch fails the error will go back via the
     *                   HTTP request.
     */
    public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
        if (log.isDebugEnabled()) {
            log.debug("Forwarding to location " + finalLocation);
        }

        PageContext pageContext = ServletActionContext.getPageContext();

        if (pageContext != null) {
            pageContext.include(finalLocation);
        } else {
            HttpServletRequest request = ServletActionContext.getRequest();
            HttpServletResponse response = ServletActionContext.getResponse();
            RequestDispatcher dispatcher = request.getRequestDispatcher(finalLocation);

            // if the view doesn't exist, let's do a 404
            if (dispatcher == null) {
                response.sendError(404, "result '" + finalLocation + "' not found");

                return;
            }

            // If we're included, then include the view
            // Otherwise do forward 
            // This allow the page to, for example, set content type 
            if (!response.isCommitted() && (request.getAttribute("javax.servlet.include.servlet_path") == null)) {
                request.setAttribute("struts.view_uri", finalLocation);
                request.setAttribute("struts.request_uri", request.getRequestURI());

                dispatcher.forward(request, response);
            } else {
                dispatcher.include(request, response);
            }
        }
    }
}