requestprocessor.java.svn-base

MVC开源框架

/*
 * $Id$
 *
 * 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 org.apache.struts.action;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.Globals;
import org.apache.struts.config.ActionConfig;
import org.apache.struts.config.ExceptionConfig;
import org.apache.struts.config.ForwardConfig;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.upload.MultipartRequestWrapper;
import org.apache.struts.util.MessageResources;
import org.apache.struts.util.RequestUtils;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import java.io.IOException;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Locale;

/**
 * <p><strong>RequestProcessor</strong> contains the processing logic that the
 * {@link ActionServlet} performs as it receives each servlet request from the
 * container. You can customize the request processing behavior by subclassing
 * this class and overriding the method(s) whose behavior you are interested
 * in changing.</p>
 *
 * @version $Rev$ $Date$
 * @since Struts 1.1
 */
public class RequestProcessor {
    // ----------------------------------------------------- Manifest Constants

    /**
     * <p>The request attribute under which the path information is stored for
     * processing during a <code>RequestDispatcher.include</code> call.</p>
     */
    public static final String INCLUDE_PATH_INFO =
        "javax.servlet.include.path_info";

    /**
     * <p>The request attribute under which the servlet path information is
     * stored for processing during a <code>RequestDispatcher.include</code>
     * call.</p>
     */
    public static final String INCLUDE_SERVLET_PATH =
        "javax.servlet.include.servlet_path";

    /**
     * <p>Commons Logging instance.</p>
     */
    protected static Log log = LogFactory.getLog(RequestProcessor.class);

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

    /**
     * <p>The set of <code>Action</code> instances that have been created and
     * initialized, keyed by the fully qualified Java class name of the
     * <code>Action</code> class.</p>
     */
    protected HashMap actions = new HashMap();

    /**
     * <p>The <code>ModuleConfiguration</code> with which we are
     * associated.</p>
     */
    protected ModuleConfig moduleConfig = null;

    /**
     * <p>The servlet with which we are associated.</p>
     */
    protected ActionServlet servlet = null;

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

    /**
     * <p>Clean up in preparation for a shutdown of this application.</p>
     */
    public void destroy() {
        synchronized (this.actions) {
            Iterator actions = this.actions.values().iterator();

            while (actions.hasNext()) {
                Action action = (Action) actions.next();

                action.setServlet(null);
            }

            this.actions.clear();
        }

        this.servlet = null;
    }

    /**
     * <p>Initialize this request processor instance.</p>
     *
     * @param servlet      The ActionServlet we are associated with
     * @param moduleConfig The ModuleConfig we are associated with.
     * @throws ServletException If an error occor during initialization
     */
    public void init(ActionServlet servlet, ModuleConfig moduleConfig)
        throws ServletException {
        synchronized (actions) {
            actions.clear();
        }

        this.servlet = servlet;
        this.moduleConfig = moduleConfig;
    }

    /**
     * <p>Process an <code>HttpServletRequest</code> and create the
     * corresponding <code>HttpServletResponse</code> or dispatch to another
     * resource.</p>
     *
     * @param request  The servlet request we are processing
     * @param response The servlet response we are creating
     * @throws IOException      if an input/output error occurs
     * @throws ServletException if a processing exception occurs
     */
    public void process(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        // Wrap multipart requests with a special wrapper
        request = processMultipart(request);

        // Identify the path component we will use to select a mapping
        String path = processPath(request, response);

        if (path == null) {
            return;
        }

        if (log.isDebugEnabled()) {
            log.debug("Processing a '" + request.getMethod() + "' for path '"
                + path + "'");
        }

        // Select a Locale for the current user if requested
        processLocale(request, response);

        // Set the content type and no-caching headers if requested
        processContent(request, response);
        processNoCache(request, response);

        // General purpose preprocessing hook
        if (!processPreprocess(request, response)) {
            return;
        }

        this.processCachedMessages(request, response);

        // Identify the mapping for this request
        ActionMapping mapping = processMapping(request, response, path);

        if (mapping == null) {
            return;
        }

        // Check for any role required to perform this action
        if (!processRoles(request, response, mapping)) {
            return;
        }

        // Process any ActionForm bean related to this request
        ActionForm form = processActionForm(request, response, mapping);

        processPopulate(request, response, form, mapping);

        // Validate any fields of the ActionForm bean, if applicable
        try {
            if (!processValidate(request, response, form, mapping)) {
                return;
            }
        } catch (InvalidCancelException e) {
            ActionForward forward = processException(request, response, e, form, mapping);
            processForwardConfig(request, response, forward);
            return;
        } catch (IOException e) {
            throw e;
        } catch (ServletException e) {
            throw e;
        }

        // Process a forward or include specified by this mapping
        if (!processForward(request, response, mapping)) {
            return;
        }

        if (!processInclude(request, response, mapping)) {
            return;
        }

        // Create or acquire the Action instance to process this request
        Action action = processActionCreate(request, response, mapping);

        if (action == null) {
            return;
        }

        // Call the Action instance itself
        ActionForward forward =
            processActionPerform(request, response, action, form, mapping);

        // Process the returned ActionForward instance
        processForwardConfig(request, response, forward);
    }

    // ----------------------------------------------------- Processing Methods

    /**
     * <p>Return an <code>Action</code> instance that will be used to process
     * the current request, creating a new one if necessary.</p>
     *
     * @param request  The servlet request we are processing
     * @param response The servlet response we are creating
     * @param mapping  The mapping we are using
     * @return An <code>Action</code> instance that will be used to process
     *         the current request.
     * @throws IOException if an input/output error occurs
     */
    protected Action processActionCreate(HttpServletRequest request,
        HttpServletResponse response, ActionMapping mapping)
        throws IOException {
        // Acquire the Action instance we will be using (if there is one)
        String className = mapping.getType();

        if (log.isDebugEnabled()) {
            log.debug(" Looking for Action instance for class " + className);
        }

        // If there were a mapping property indicating whether
        // an Action were a singleton or not ([true]),
        // could we just instantiate and return a new instance here?
        Action instance;

        synchronized (actions) {
            // Return any existing Action instance of this class
            instance = (Action) actions.get(className);

            if (instance != null) {
                if (log.isTraceEnabled()) {
                    log.trace("  Returning existing Action instance");
                }

                return (instance);
            }

            // Create and return a new Action instance
            if (log.isTraceEnabled()) {
                log.trace("  Creating new Action instance");
            }

            try {
                instance = (Action) RequestUtils.applicationInstance(className);

                // Maybe we should propagate this exception
                // instead of returning null.
            } catch (Exception e) {
                log.error(getInternal().getMessage("actionCreate",
                        mapping.getPath()), e);

                response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                    getInternal().getMessage("actionCreate", mapping.getPath()));

                return (null);
            }

            actions.put(className, instance);
        }

        if (instance.getServlet() == null) {
            instance.setServlet(this.servlet);
        }

        return (instance);
    }

    /**
     * <p>Retrieve and return the <code>ActionForm</code> associated with this
     * mapping, creating and retaining one if necessary. If there is no
     * <code>ActionForm</code> associated with this mapping, return
     * <code>null</code>.</p>
     *
     * @param request  The servlet request we are processing
     * @param response The servlet response we are creating
     * @param mapping  The mapping we are using
     * @return The <code>ActionForm</code> associated with this mapping.
     */
    protected ActionForm processActionForm(HttpServletRequest request,
        HttpServletResponse response, ActionMapping mapping) {
        // Create (if necessary) a form bean to use
        ActionForm instance =
            RequestUtils.createActionForm(request, mapping, moduleConfig,
                servlet);

        if (instance == null) {
            return (null);
        }

        // Store the new instance in the appropriate scope
        if (log.isDebugEnabled()) {
            log.debug(" Storing ActionForm bean instance in scope '"
                + mapping.getScope() + "' under attribute key '"
                + mapping.getAttribute() + "'");
        }

        if ("request".equals(mapping.getScope())) {
            request.setAttribute(mapping.getAttribute(), instance);
        } else {
            HttpSession session = request.getSession();

            session.setAttribute(mapping.getAttribute(), instance);
        }

        return (instance);
    }

    /**
     * <p>Forward or redirect to the specified destination, by the specified
     * mechanism.  This method uses a <code>ForwardConfig</code> object
     * instead an <code>ActionForward</code>.</p>
     *
     * @param request  The servlet request we are processing
     * @param response The servlet response we are creating
     * @param forward  The ForwardConfig controlling where we go next
     * @throws IOException      if an input/output error occurs
     * @throws ServletException if a servlet exception occurs
     */
    protected void processForwardConfig(HttpServletRequest request,
        HttpServletResponse response, ForwardConfig forward)
        throws IOException, ServletException {
        if (forward == null) {
            return;
        }

        if (log.isDebugEnabled()) {
            log.debug("processForwardConfig(" + forward + ")");
        }

        String forwardPath = forward.getPath();
        String uri;

        // If the forward can be unaliased into an action, then use the path of the action
        String actionIdPath = RequestUtils.actionIdURL(forward, request, servlet);
        if (actionIdPath != null) {
            forwardPath = actionIdPath;
            ForwardConfig actionIdForward = new ForwardConfig(forward);
            actionIdForward.setPath(actionIdPath);
            forward = actionIdForward;
        }