/*
 * $Id: ActionServlet.java 505729 2007-02-10 17:56:46Z pbenedict $
 *
 * 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.beanutils.BeanUtils;
import org.apache.commons.beanutils.ConvertUtils;
import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.beanutils.converters.BigDecimalConverter;
import org.apache.commons.beanutils.converters.BigIntegerConverter;
import org.apache.commons.beanutils.converters.BooleanConverter;
import org.apache.commons.beanutils.converters.ByteConverter;
import org.apache.commons.beanutils.converters.CharacterConverter;
import org.apache.commons.beanutils.converters.DoubleConverter;
import org.apache.commons.beanutils.converters.FloatConverter;
import org.apache.commons.beanutils.converters.IntegerConverter;
import org.apache.commons.beanutils.converters.LongConverter;
import org.apache.commons.beanutils.converters.ShortConverter;
import org.apache.commons.chain.CatalogFactory;
import org.apache.commons.chain.config.ConfigParser;
import org.apache.commons.digester.Digester;
import org.apache.commons.digester.RuleSet;
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.ConfigRuleSet;
import org.apache.struts.config.ExceptionConfig;
import org.apache.struts.config.FormBeanConfig;
import org.apache.struts.config.FormPropertyConfig;
import org.apache.struts.config.ForwardConfig;
import org.apache.struts.config.MessageResourcesConfig;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.config.ModuleConfigFactory;
import org.apache.struts.config.PlugInConfig;
import org.apache.struts.util.MessageResources;
import org.apache.struts.util.MessageResourcesFactory;
import org.apache.struts.util.ModuleUtils;
import org.apache.struts.util.RequestUtils;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

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

import java.io.IOException;
import java.io.InputStream;

import java.math.BigDecimal;
import java.math.BigInteger;

import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.MissingResourceException;

/**
 * <p><strong>ActionServlet</strong> provides the "controller" in the
 * Model-View-Controller (MVC) design pattern for web applications that is
 * commonly known as "Model 2".  This nomenclature originated with a
 * description in the JavaServerPages Specification, version 0.92, and has
 * persisted ever since (in the absence of a better name).</p>
 *
 * <p>Generally, a "Model 2" application is architected as follows:</p>
 *
 * <ul>
 *
 * <li>The user interface will generally be created with server pages, which
 * will not themselves contain any business logic. These pages represent the
 * "view" component of an MVC architecture.</li>
 *
 * <li>Forms and hyperlinks in the user interface that require business logic
 * to be executed will be submitted to a request URI that is mapped to this
 * servlet.</li>
 *
 * <li>There can be <b>one</b> instance of this servlet class, which receives
 * and processes all requests that change the state of a user's interaction
 * with the application. The servlet delegates the handling of a request to a
 * {@link RequestProcessor} object. This component represents the "controller"
 * component of an MVC architecture. </li>
 *
 * <li>The <code>RequestProcessor</code> selects and invokes an {@link Action}
 * class to perform the requested business logic, or delegates the response to
 * another resource.</li>
 *
 * <li>The <code>Action</code> classes can manipulate the state of the
 * application's interaction with the user, typically by creating or modifying
 * JavaBeans that are stored as request or session attributes (depending on
 * how long they need to be available). Such JavaBeans represent the "model"
 * component of an MVC architecture.</li>
 *
 * <li>Instead of producing the next page of the user interface directly,
 * <code>Action</code> classes generally return an {@link ActionForward} to
 * indicate which resource should handle the response. If the
 * <code>Action</code> does not return null, the <code>RequestProcessor</code>
 * forwards or redirects to the specified resource (by utilizing
 * <code>RequestDispatcher.forward</code> or <code>Response.sendRedirect</code>)
 * so as to produce the next page of the user interface.</li>
 *
 * </ul>
 *
 * <p>The standard version of <code>RequestsProcessor</code> implements the
 * following logic for each incoming HTTP request. You can override some or
 * all of this functionality by subclassing this object and implementing your
 * own version of the processing.</p>
 *
 * <ul>
 *
 * <li>Identify, from the incoming request URI, the substring that will be
 * used to select an action procedure.</li>
 *
 * <li>Use this substring to map to the Java class name of the corresponding
 * action class (an implementation of the <code>Action</code> interface).
 * </li>
 *
 * <li>If this is the first request for a particular <code>Action</code>
 * class, instantiate an instance of that class and cache it for future
 * use.</li>
 *
 * <li>Optionally populate the properties of an <code>ActionForm</code> bean
 * associated with this mapping.</li>
 *
 * <li>Call the <code>execute</code> method of this <code>Action</code> class,
 * passing on a reference to the mapping that was used, the relevant form-bean
 * (if any), and the request and the response that were passed to the
 * controller by the servlet container (thereby providing access to any
 * specialized properties of the mapping itself as well as to the
 * ServletContext). </li>
 *
 * </ul>
 *
 * <p>The standard version of <code>ActionServlet</code> is configured based
 * on the following servlet initialization parameters, which you will specify
 * in the web application deployment descriptor (<code>/WEB-INF/web.xml</code>)
 * for your application.  Subclasses that specialize this servlet are free to
 * define additional initialization parameters. </p>
 *
 * <ul>
 *
 * <li><strong>config</strong> - Comma-separated list of context-relative
 * path(s) to the XML resource(s) containing the configuration information for
 * the default module.  (Multiple files support since Struts 1.1)
 * [/WEB-INF/struts-config.xml].</li>
 *
 * <li><strong>config/${module}</strong> - Comma-separated list of
 * Context-relative path(s) to the XML resource(s) containing the
 * configuration information for the module that will use the specified prefix
 * (/${module}). This can be repeated as many times as required for multiple
 * modules. (Since Struts 1.1)</li>
 *
 * <li><strong>configFactory</strong> - The Java class name of the
 * <code>ModuleConfigFactory</code> used to create the implementation of the
 * ModuleConfig interface. </li>
 *
 * <li><strong>convertNull</strong> - Force simulation of the Struts 1.0
 * behavior when populating forms. If set to true, the numeric Java wrapper
 * class types (like <code>java.lang.Integer</code>) will default to null
 * (rather than 0). (Since Struts 1.1) [false] </li>
 *
 * <li><strong>rulesets </strong> - Comma-delimited list of fully qualified
 * classnames of additional <code>org.apache.commons.digester.RuleSet</code>
 * instances that should be added to the <code>Digester</code> that will be
 * processing <code>struts-config.xml</code> files.  By default, only the
 * <code>RuleSet</code> for the standard configuration elements is loaded.
 * (Since Struts 1.1)</li>
 *
 * <li><strong>validating</strong> - Should we use a validating XML parser to
 * process the configuration file (strongly recommended)? [true]</li>
 *
 * <li><strong>chainConfig</strong> - Comma-separated list of either
 * context-relative or classloader path(s) to load commons-chain catalog
 * definitions from.  If none specified, the default Struts catalog that is
 * provided with Struts will be used.</li>
 *
 * </ul>
 *
 * @version $Rev: 505729 $ $Date: 2005-10-14 19:54:16 -0400 (Fri, 14 Oct 2005)
 *          $
 */
public class ActionServlet extends HttpServlet {
    /**
     * <p>Commons Logging instance.</p>
     *
     * @since Struts 1.1
     */
    protected static Log log = LogFactory.getLog(ActionServlet.class);

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

    /**
     * <p>Comma-separated list of context-relative path(s) to our
     * configuration resource(s) for the default module.</p>
     */
    protected String config = "/WEB-INF/struts-config.xml";

    /**
     * <p>Comma-separated list of context or classloader-relative path(s) that
     * contain the configuration for the default commons-chain
     * catalog(s).</p>
     */
    protected String chainConfig = "org/apache/struts/chain/chain-config.xml";

    /**
     * <p>The Digester used to produce ModuleConfig objects from a Struts
     * configuration file.</p>
     *
     * @since Struts 1.1
     */
    protected Digester configDigester = null;

    /**
     * <p>The flag to request backwards-compatible conversions for form bean
     * properties of the Java wrapper class types.</p>
     *
     * @since Struts 1.1
     */
    protected boolean convertNull = false;

    /**
     * <p>The resources object for our internal resources.</p>
     */
    protected MessageResources internal = null;

    /**
     * <p>The Java base name of our internal resources.</p>
     *
     * @since Struts 1.1
     */
    protected String internalName = "org.apache.struts.action.ActionResources";

    /**
     * <p>The set of public identifiers, and corresponding resource names, for
     * the versions of the configuration file DTDs that we know about.  There
     * <strong>MUST</strong> be an even number of Strings in this list!</p>
     */
    protected String[] registrations =
        {
            "-//Apache Software Foundation//DTD Struts Configuration 1.0//EN",
            "/org/apache/struts/resources/struts-config_1_0.dtd",
            "-//Apache Software Foundation//DTD Struts Configuration 1.1//EN",
            "/org/apache/struts/resources/struts-config_1_1.dtd",
            "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN",
            "/org/apache/struts/resources/struts-config_1_2.dtd",
            "-//Apache Software Foundation//DTD Struts Configuration 1.3//EN",
            "/org/apache/struts/resources/struts-config_1_3.dtd",
            "-//Apache Software Foundation//DTD Struts Configuration 1.4//EN",
            "/org/apache/struts/resources/struts-config_1_4.dtd",
            "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN",
            "/org/apache/struts/resources/web-app_2_3.dtd"
        };

    /**
     * <p>The URL pattern to which we are mapped in our web application
     * deployment descriptor.</p>
     */
    protected String servletMapping = null; // :FIXME: - multiples?

    /**
     * <p>The servlet name under which we are registered in our web
     * application deployment descriptor.</p>
     */
    protected String servletName = null;

    // ---------------------------------------------------- HttpServlet Methods

    /**
     * <p>Gracefully shut down this controller servlet, releasing any
     * resources that were allocated at initialization.</p>
     */
    public void destroy() {
        if (log.isDebugEnabled()) {
            log.debug(internal.getMessage("finalizing"));
        }

        destroyModules();
        destroyInternal();
        getServletContext().removeAttribute(Globals.ACTION_SERVLET_KEY);

        // Release our LogFactory and Log instances (if any)
        ClassLoader classLoader =
            Thread.currentThread().getContextClassLoader();

        if (classLoader == null) {
            classLoader = ActionServlet.class.getClassLoader();
        }

        try {
            LogFactory.release(classLoader);
        } catch (Throwable t) {
            ; // Servlet container doesn't have the latest version

            // of commons-logging-api.jar installed
            // :FIXME: Why is this dependent on the container's version of
            // commons-logging? Shouldn't this depend on the version packaged
            // with Struts?

            /*
              Reason: LogFactory.release(classLoader); was added as
              an attempt to investigate the OutOfMemory error reported on
              Bugzilla #14042. It was committed for version 1.136 by craigmcc
            */
        }

        CatalogFactory.clear();
        PropertyUtils.clearDescriptors();
    }

    /**
     * <p>Initialize this servlet.  Most of the processing has been factored
     * into support methods so that you can override particular functionality
     * at a fairly granular level.</p>
     *