/*
 * Copyright 2002-2008 the original author or authors.
 *
 * 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.springframework.web.portlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import javax.portlet.ActionRequest;
import javax.portlet.ActionResponse;
import javax.portlet.PortletException;
import javax.portlet.PortletRequest;
import javax.portlet.PortletResponse;
import javax.portlet.PortletSession;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;
import javax.portlet.UnavailableException;

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

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.i18n.LocaleContext;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.context.i18n.SimpleLocaleContext;
import org.springframework.core.JdkVersion;
import org.springframework.core.OrderComparator;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.portlet.context.PortletRequestAttributes;
import org.springframework.web.portlet.multipart.MultipartActionRequest;
import org.springframework.web.portlet.multipart.PortletMultipartResolver;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.ViewRendererServlet;
import org.springframework.web.servlet.ViewResolver;

/**
 * Central dispatcher for use within the Portlet MVC framework, e.g. for web UI
 * controllers. Dispatches to registered handlers for processing a portlet request.
 *
 * <p>This portlet is very flexible: It can be used with just about any workflow,
 * with the installation of the appropriate adapter classes. It offers the
 * following functionality that distinguishes it from other request-driven
 * portlet MVC frameworks:
 *
 * <ul>
 * <li>It is based around a JavaBeans configuration mechanism.
 *
 * <li>It can use any {@link HandlerMapping} implementation - pre-built or provided
 * as part of an application - to control the routing of requests to handler objects.
 * Default is a {@link org.springframework.web.portlet.mvc.annotation.DefaultAnnotationHandlerMapping}
 * on Java 5+; there is no default on Java 1.4. HandlerMapping objects can be defined as
 * beans in the portlet's application context, implementing the HandlerMapping interface,
 * overriding the default HandlerMapping if present. HandlerMappings can be given any
 * bean name (they are tested by type).
 *
 * <li>It can use any {@link HandlerAdapter}; this allows for using any handler interface.
 * The default adapter is {@link org.springframework.web.portlet.mvc.SimpleControllerHandlerAdapter}
 * for Spring's {@link org.springframework.web.portlet.mvc.Controller} interface.
 * When running in a Java 5+ environment, a default
 * {@link org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter}
 * will be registered as well. HandlerAdapter objects can be added as beans in the
 * application context, overriding the default HandlerAdapter. Like HandlerMappings,
 * HandlerAdapters can be given any bean name (they are tested by type).
 *
 * <li>The dispatcher's exception resolution strategy can be specified via a
 * {@link HandlerExceptionResolver}, for example mapping certain exceptions to
 * error pages. Default is none. Additional HandlerExceptionResolvers can be added
 * through the application context. HandlerExceptionResolver can be given any
 * bean name (they are tested by type).
 *
 * <li>Its view resolution strategy can be specified via a {@link ViewResolver}
 * implementation, resolving symbolic view names into View objects. Default is
 * {@link org.springframework.web.servlet.view.InternalResourceViewResolver}.
 * ViewResolver objects can be added as beans in the application context,
 * overriding the default ViewResolver. ViewResolvers can be given any bean name
 * (they are tested by type).
 *
 * <li>The dispatcher's strategy for resolving multipart requests is determined by a
 * {@link org.springframework.web.portlet.multipart.PortletMultipartResolver} implementation.
 * An implementations for Jakarta Commons FileUpload is included:
 * {@link org.springframework.web.portlet.multipart.CommonsPortletMultipartResolver}.
 * The MultipartResolver bean name is "portletMultipartResolver"; default is none.
 * </ul>
 *
 * <p><b>NOTE: The <code>@RequestMapping</code> annotation will only be processed
 * if a corresponding <code>HandlerMapping</code> (for type level annotations)
 * and/or <code>HandlerAdapter</code> (for method level annotations)
 * is present in the dispatcher.</b> This is the case by default.
 * However, if you are defining custom <code>HandlerMappings</code> or
 * <code>HandlerAdapters</code>, then you need to make sure that a
 * corresponding custom <code>DefaultAnnotationHandlerMapping</code>
 * and/or <code>AnnotationMethodHandlerAdapter</code> is defined as well
 * - provided that you intend to use <code>@RequestMapping</code>.
 *
 * <p><b>A web application can define any number of DispatcherPortlets.</b>
 * Each portlet will operate in its own namespace, loading its own application
 * context with mappings, handlers, etc. Only the root application context
 * as loaded by {@link org.springframework.web.context.ContextLoaderListener},
 * if any, will be shared.
 *
 * <p>Thanks to Rainer Schmitz and Nick Lothian for their suggestions!
 *
 * @author William G. Thompson, Jr.
 * @author John A. Lewis
 * @author Juergen Hoeller
 * @since 2.0
 * @see org.springframework.web.portlet.mvc.Controller
 * @see org.springframework.web.servlet.ViewRendererServlet
 * @see org.springframework.web.context.ContextLoaderListener
 */
public class DispatcherPortlet extends FrameworkPortlet {

	/**
	 * Well-known name for the PortletMultipartResolver object in the bean factory for this namespace.
	 */
	public static final String MULTIPART_RESOLVER_BEAN_NAME = "portletMultipartResolver";

	/**
	 * Well-known name for the HandlerMapping object in the bean factory for this namespace.
	 * Only used when "detectAllHandlerMappings" is turned off.
	 * @see #setDetectAllViewResolvers
	 */
	public static final String HANDLER_MAPPING_BEAN_NAME = "handlerMapping";

	/**
	 * Well-known name for the HandlerAdapter object in the bean factory for this namespace.
	 * Only used when "detectAllHandlerAdapters" is turned off.
	 * @see #setDetectAllHandlerAdapters
	 */
	public static final String HANDLER_ADAPTER_BEAN_NAME = "handlerAdapter";

	/**
	 * Well-known name for the HandlerExceptionResolver object in the bean factory for this
	 * namespace. Only used when "detectAllHandlerExceptionResolvers" is turned off.
	 * @see #setDetectAllViewResolvers
	 */
	public static final String HANDLER_EXCEPTION_RESOLVER_BEAN_NAME = "handlerExceptionResolver";

	/**
	 * Well-known name for the ViewResolver object in the bean factory for this namespace.
	 */
	public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver";

	/**
	 * Default URL to ViewRendererServlet. This bridge servlet is used to convert
	 * portlet render requests to servlet requests in order to leverage the view support
	 * in the <code>org.springframework.web.view</code> package.
	 */
	public static final String DEFAULT_VIEW_RENDERER_URL = "/WEB-INF/servlet/view";

	/**
	 * Request attribute to hold the currently chosen HandlerExecutionChain.
	 * Only used for internal optimizations.
	 */
	public static final String HANDLER_EXECUTION_CHAIN_ATTRIBUTE =
			DispatcherPortlet.class.getName() + ".HANDLER";

	/**
	 * Unlike the Servlet version of this class, we have to deal with the
	 * two-phase nature of the portlet request. To do this, we need to pass
	 * forward any exception that occurs during the action phase, so that
	 * it can be displayed in the render phase. The only direct way to pass
	 * things forward and preserve them for each render request is through
	 * render parameters, but these are limited to String objects and we need
	 * to pass the Exception itself. The only other way to do this is in the
	 * session. The bad thing about using the session is that we have no way
	 * of knowing when we are done re-rendering the request and so we don't
	 * know when we can remove the objects from the session. So we will end
	 * up polluting the session with an old exception when we finally leave
	 * the render phase of one request and move on to something else.
	 */
	public static final String ACTION_EXCEPTION_SESSION_ATTRIBUTE =
			DispatcherPortlet.class.getName() + ".ACTION_EXCEPTION";

	/**
	 * This render parameter is used to indicate forward to the render phase
	 * that an exception occurred during the action phase.
	 */
	public static final String ACTION_EXCEPTION_RENDER_PARAMETER = "actionException";

	/**
	 * Log category to use when no mapped handler is found for a request.
	 */
	public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.portlet.PageNotFound";

	/**
	 * Name of the class path resource (relative to the DispatcherPortlet class)
	 * that defines DispatcherPortet's default strategy names.
	 */
	private static final String DEFAULT_STRATEGIES_PATH = "DispatcherPortlet.properties";


	/**
	 * Additional logger to use when no mapped handler is found for a request.
	 */
	protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY);

	private static final Properties defaultStrategies;

	static {
		// Load default strategy implementations from properties file.
		// This is currently strictly internal and not meant to be customized
		// by application developers.
		try {
			ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherPortlet.class);
			defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
		}
		catch (IOException ex) {
			throw new IllegalStateException("Could not load 'DispatcherPortlet.properties': " + ex.getMessage());
		}
	}


	/** Detect all HandlerMappings or just expect "handlerMapping" bean? */
	private boolean detectAllHandlerMappings = true;

	/** Detect all HandlerAdapters or just expect "handlerAdapter" bean? */
	private boolean detectAllHandlerAdapters = true;

	/** Detect all HandlerExceptionResolvers or just expect "handlerExceptionResolver" bean? */
	private boolean detectAllHandlerExceptionResolvers = true;

	/** Detect all ViewResolvers or just expect "viewResolver" bean? */
	private boolean detectAllViewResolvers = true;

	/** URL that points to the ViewRendererServlet */
	private String viewRendererUrl = DEFAULT_VIEW_RENDERER_URL;

	/** Expose LocaleContext and RequestAttributes as inheritable for child threads? */
	private boolean threadContextInheritable = false;


	/** MultipartResolver used by this portlet */
	private PortletMultipartResolver multipartResolver;

	/** List of HandlerMappings used by this portlet */
	private List handlerMappings;

	/** List of HandlerAdapters used by this portlet */
	private List handlerAdapters;

	/** List of HandlerExceptionResolvers used by this portlet */
	private List handlerExceptionResolvers;

	/** List of ViewResolvers used by this portlet */
	private List viewResolvers;


	/**
	 * Set whether to detect all HandlerMapping beans in this portlet's context.
	 * Else, just a single bean with name "handlerMapping" will be expected.
	 * <p>Default is true. Turn this off if you want this portlet to use a
	 * single HandlerMapping, despite multiple HandlerMapping beans being
	 * defined in the context.
	 */
	public void setDetectAllHandlerMappings(boolean detectAllHandlerMappings) {
		this.detectAllHandlerMappings = detectAllHandlerMappings;
	}

	/**
	 * Set whether to detect all HandlerAdapter beans in this portlet's context.
	 * Else, just a single bean with name "handlerAdapter" will be expected.
	 * <p>Default is "true". Turn this off if you want this portlet to use a
	 * single HandlerAdapter, despite multiple HandlerAdapter beans being
	 * defined in the context.
	 */