switchaction.java

这是一个轻便的j2ee的web应用框架,是一个在多个项目中运用的实际框架,采用struts,hebinate,xml等技术,有丰富的tag,role,navigation,session,dictio

/*
 * $Header: /sfroot/cvs/esimple/src/core/org/apache/struts/actions/SwitchAction.java,v 1.1.1.1 2004/09/08 06:38:32 lava Exp $
 * $Revision: 1.1.1.1 $
 * $Date: 2004/09/08 06:38:32 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2002 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", "Struts", 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"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * 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/>.
 *
 */

package org.apache.struts.actions;


import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.util.MessageResources;
import org.apache.struts.util.RequestUtils;
import org.apache.struts.Globals;


/**
 * <p>A standard <strong>Action</strong> that switches to a new module
 * and then forwards control to a URI (specified in a number of possible ways)
 * within the new module.</p>
 *
 * <p>Valid request parameters for this Action are:</p>
 * <ul>
 * <li><strong>page</strong> - Module-relative URI (beginning with "/")
 *     to which control should be forwarded after switching.</li>
 * <li><strong>prefix</strong> - The module prefix (beginning with "/")
 *     of the module to which control should be switched.  Use a
 *     zero-length string for the default module.  The
 *     appropriate <code>ModuleConfig</code> object will be stored as a
 *     request attribute, so any subsequent logic will assume the new
 *     module.</li>
 * </ul>
 *
 * @author Craig R. McClanahan
 * @version $Revision: 1.1.1.1 $ $Date: 2004/09/08 06:38:32 $
 * @since Struts 1.1
 */

public class SwitchAction extends Action {


    // ----------------------------------------------------- Instance Variables


    /**
     * Commons Logging instance.
     */
    protected static Log log = LogFactory.getLog(SwitchAction.class);


    /**
     * The message resources for this package.
     */
    protected static MessageResources messages =
        MessageResources.getMessageResources
        ("org.apache.struts.actions.LocalStrings");


    // --------------------------------------------------------- Public Methods


    /**
     * Process the specified HTTP request, and create the corresponding HTTP
     * response (or forward to another web component that will create it),
     * with provision for handling exceptions thrown by the business logic.
     *
     * @param mapping The ActionMapping used to select this instance
     * @param form The optional ActionForm bean for this request (if any)
     * @param request The HTTP request we are processing
     * @param response The HTTP response we are creating
     *
     * @exception Exception if the application business logic throws
     *  an exception
     */
    public ActionForward execute(ActionMapping mapping,
                                 ActionForm form,
                                 HttpServletRequest request,
                                 HttpServletResponse response)
        throws Exception {

        // Identify the request parameters controlling our actions
        String page = request.getParameter("page");
        String prefix = request.getParameter("prefix");
        if ((page == null) || (prefix == null)) {
            String message = messages.getMessage("switch.required");
            log.error(message);
            response.sendError(HttpServletResponse.SC_BAD_REQUEST,
                               message);
            return (null);
        }

        // Switch to the requested module
        RequestUtils.selectModule(prefix, request,
                                       getServlet().getServletContext());
        if (request.getAttribute(Globals.MODULE_KEY) == null) {
            String message = messages.getMessage("switch.prefix", prefix);
            log.error(message);
            response.sendError(HttpServletResponse.SC_BAD_REQUEST,
                               message);
            return (null);
        }

        // Forward control to the specified module-relative URI
        return (new ActionForward(page));

    }


}