composablerequestprocessor.java

structs源码

/*
 * $Id: ComposableRequestProcessor.java 471754 2006-11-06 14:55:09Z husted $
 *
 * 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.chain;

import org.apache.commons.beanutils.ConstructorUtils;
import org.apache.commons.chain.Catalog;
import org.apache.commons.chain.CatalogFactory;
import org.apache.commons.chain.Command;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.RequestProcessor;
import org.apache.struts.chain.contexts.ActionContext;
import org.apache.struts.chain.contexts.ServletActionContext;
import org.apache.struts.config.ControllerConfig;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.upload.MultipartRequestWrapper;
import org.apache.struts.util.RequestUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.lang.reflect.Constructor;

/**
 * <p> ComposableRequestProcessor uses the Chain Of Resposibility design
 * pattern (as implemented by the commons-chain package in Jakarta Commons) to
 * support external configuration of command chains to be used.  It is
 * configured via the following context initialization parameters: </p>
 *
 * <ul>
 *
 * <li>[org.apache.struts.chain.CATALOG_NAME] - Name of the Catalog in which
 * we will look up the Command to be executed for each request.  If not
 * specified, the default value is struts. </li>
 *
 * <li> org.apache.struts.chain.COMMAND_NAME - Name of the Command which we
 * will execute for each request, to be looked up in the specified Catalog.
 * If not specified, the default value is servlet-standard. </li>
 *
 * </ul>
 *
 * @version $Rev: 471754 $ $Date: 2005-11-12 13:01:44 -0500 (Sat, 12 Nov 2005)
 *          $
 * @since Struts 1.1
 */
public class ComposableRequestProcessor extends RequestProcessor {
    // ------------------------------------------------------ Instance Variables

    /**
     * <p> Cache for constructor discovered by setActionContextClass method.
     * </p>
     */
    private static final Class[] SERVLET_ACTION_CONTEXT_CTOR_SIGNATURE =
        new Class[] {
            ServletContext.class, HttpServletRequest.class,
            HttpServletResponse.class
        };

    /**
     * <p> Token for ActionContext clazss so that it can be stored in the
     * ControllerConfig. </p>
     */
    public static final String ACTION_CONTEXT_CLASS = "ACTION_CONTEXT_CLASS";

    /**
     * <p>The <code>Log</code> instance for this class.</p>
     */
    protected static final Log LOG =
        LogFactory.getLog(ComposableRequestProcessor.class);

    /**
     * <p>The {@link CatalogFactory} from which catalog containing the the
     * base request-processing {@link Command} will be retrieved.</p>
     */
    protected CatalogFactory catalogFactory = null;

    /**
     * <p>The {@link Catalog} containing all of the available command chains
     * for this module.
     */
    protected Catalog catalog = null;

    /**
     * <p>The {@link Command} to be executed for each request.</p>
     */
    protected Command command = null;

    /**
     * <p> ActionContext class as cached by createActionContextInstance
     * method. </p>
     */
    private Class actionContextClass;

    /**
     * <p> ActionContext constructor as cached by createActionContextInstance
     * method. </p>
     */
    private Constructor servletActionContextConstructor = null;

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

    /**
     * <p>Clean up in preparation for a shutdown of this application.</p>
     */
    public void destroy() {
        super.destroy();
        catalogFactory = null;
        catalog = null;
        command = null;
        actionContextClass = null;
        servletActionContextConstructor = 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 occurs during initialization
     */
    public void init(ActionServlet servlet, ModuleConfig moduleConfig)
        throws ServletException {
        LOG.info(
            "Initializing composable request processor for module prefix '"
            + moduleConfig.getPrefix() + "'");
        super.init(servlet, moduleConfig);

        initCatalogFactory(servlet, moduleConfig);

        ControllerConfig controllerConfig = moduleConfig.getControllerConfig();

        String catalogName = controllerConfig.getCatalog();

        catalog = this.catalogFactory.getCatalog(catalogName);

        if (catalog == null) {
            throw new ServletException("Cannot find catalog '" + catalogName
                + "'");
        }

        String commandName = controllerConfig.getCommand();

        command = catalog.getCommand(commandName);

        if (command == null) {
            throw new ServletException("Cannot find command '" + commandName
                + "'");
        }

        this.setActionContextClassName(controllerConfig.getProperty(
                ACTION_CONTEXT_CLASS));
    }

    /**
     * <p> Set and cache ActionContext class. </p><p> If there is a custom
     * class provided and if it uses our "preferred" constructor, cache a
     * reference to that constructor rather than looking it up every time.
     * </p>
     *
     * @param actionContextClass The ActionContext class to process
     */
    private void setActionContextClass(Class actionContextClass) {
        this.actionContextClass = actionContextClass;

        if (actionContextClass != null) {
            this.servletActionContextConstructor =
                ConstructorUtils.getAccessibleConstructor(actionContextClass,
                    SERVLET_ACTION_CONTEXT_CTOR_SIGNATURE);
        } else {
            this.servletActionContextConstructor = null;
        }
    }

    /**
     * <p>Make sure that the specified <code>className</code> identfies a
     * class which can be found and which implements the
     * <code>ActionContext</code> interface.</p>
     *
     * @param className Fully qualified name of
     * @throws ServletException     If an error occurs during initialization