dispatcherservlet.java

一个关于Spring框架的示例应用程序,简单使用,可以参考.

/*
 * Copyright 2002-2004 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.servlet;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

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

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

import org.springframework.beans.BeanUtils;
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.ApplicationContextAware;
import org.springframework.core.OrderComparator;
import org.springframework.core.io.ClassPathResource;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.util.UrlPathHelper;

/**
 * Central dispatcher for use within the web MVC framework,
 * e.g. for web UI controllers or HTTP-based remote service exporters.
 * Dispatches to registered handlers for processing a web request.
 *
 * <p>This servlet 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
 * web MVC frameworks:
 *
 * <ul>
 * <li>It is based around a JavaBeans configuration mechanism.
 *
 * <li>It can use any HandlerMapping implementation - whether standard, or provided
 * as part of an application - to control the routing of requests to handler objects.
 * Default is BeanNameUrlHandlerMapping. HandlerMapping objects can be define as beans
 * in the servlet's application context that implement the HandlerMapping interface.
 * HandlerMappings can be given any bean name (they are tested by type).
 *
 * <li>It can use any HandlerAdapter; this allows to use any handler interface.
 * Default is SimpleControllerHandlerAdapter, for Spring's Controller interface.
 * Additional HandlerAdapter objects can be added through the application context.
 * Like HandlerMappings, HandlerAdapters can be given any bean name (tested by type).
 *
 * <li>Its exception resolution strategy can be specified via a 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 (tested by type).
 *
 * <li>Its view resolution strategy can be specified via a ViewResolver implementation,
 * resolving symbolic view names into View objects. Default is InternalResourceViewResolver.
 * Additional ViewResolver objects can be added through the application context.
 * ViewResolvers can be given any bean name (tested by type).
 *
 * <li>Its strategy for resolving multipart requests is determined by a MultipartResolver
 * implementation. Implementations for Jakarta Commons FileUpload and Jason Hunter's COS
 * are included. The MultipartResolver bean name is "multipartResolver"; default is none.
 *
 * <li>Its locale resolution strategy is determined by a LocaleResolver implementation.
 * Out-of-the-box implementations work via HTTP accept header, cookie, or session.
 * The LocaleResolver bean name is "localeResolver"; default is AcceptHeaderLocaleResolver.
 *
 * <li>Its theme resolution strategy is determined by a ThemeResolver implementation.
 * Implementations for a fixed theme and for cookie and session storage are included.
 * The ThemeResolver bean name is "themeResolver"; default is FixedThemeResolver.
 * </ul>
 *
 * <p><b>A web application can use any number of DispatcherServlets.</b> Each servlet
 * will operate in its own namespace. Only the root application context will be shared.
 *
 * <p>This class and the MVC approach it delivers is discussed in Chapter 12 of
 * <a href="http://www.amazon.com/exec/obidos/tg/detail/-/0764543857/">Expert One-On-One J2EE Design and Development</a>
 * by Rod Johnson (Wrox, 2002). Note that it is called <i>ControllerServlet</i> there;
 * it has been renamed since to emphasize its dispatching role and avoid confusion
 * with Controller objects that the DispatcherServlet will dispatch to.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see org.springframework.web.context.ContextLoaderListener
 * @see HandlerMapping
 * @see org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping
 * @see HandlerAdapter
 * @see org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter
 * @see org.springframework.web.servlet.mvc.Controller
 * @see HandlerExceptionResolver
 * @see org.springframework.web.servlet.handler.SimpleMappingExceptionResolver
 * @see ViewResolver
 * @see org.springframework.web.servlet.view.InternalResourceViewResolver
 * @see MultipartResolver
 * @see org.springframework.web.multipart.commons.CommonsMultipartResolver
 * @see LocaleResolver
 * @see org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver
 * @see ThemeResolver
 * @see org.springframework.web.servlet.theme.FixedThemeResolver
 */
public class DispatcherServlet extends FrameworkServlet {

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

	/**
	 * Well-known name for the LocaleResolver object in the bean factory for this namespace.
	 */
	public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver";

	/**
	 * Well-known name for the ThemeResolver object in the bean factory for this namespace.
	 */
	public static final String THEME_RESOLVER_BEAN_NAME = "themeResolver";

	/**
	 * 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 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.
	 * Only used when "detectAllViewResolvers" is turned off.
	 * @see #setDetectAllViewResolvers
	 */
	public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver";


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

	/**
	 * Request attribute to hold current web application context.
	 * Otherwise only the global web app context is obtainable by tags etc.
	 * @see org.springframework.web.servlet.support.RequestContextUtils#getWebApplicationContext
	 */
	public static final String WEB_APPLICATION_CONTEXT_ATTRIBUTE = DispatcherServlet.class.getName() + ".CONTEXT";

	/**
	 * Request attribute to hold current multipart resolver, retrievable by views/binders.
	 * @see org.springframework.web.servlet.support.RequestContextUtils#getMultipartResolver
	 */
	public static final String MULTIPART_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".MULTIPART";

	/**
	 * Request attribute to hold current locale, retrievable by views.
	 * @see org.springframework.web.servlet.support.RequestContextUtils#getLocaleResolver
	 */
	public static final String LOCALE_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".LOCALE";

	/**
	 * Request attribute to hold current theme, retrievable by views.
	 * @see org.springframework.web.servlet.support.RequestContextUtils#getThemeResolver
	 */
	public static final String THEME_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME";


	/**
	 * 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.servlet.PageNotFound";

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

	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, DispatcherServlet.class);
			InputStream is = resource.getInputStream();
			try {
				defaultStrategies.load(is);
			}
			finally {
				is.close();
			}
		}
		catch (IOException ex) {
			throw new IllegalStateException("Could not load 'DispatcherServlet.properties': " + ex.getMessage());
		}
	}


	/** Perform cleanup of request attributes after include request? */
	private boolean cleanupAfterInclude = true;

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

	/** MultipartResolver used by this servlet */
	private MultipartResolver multipartResolver;

	/** LocaleResolver used by this servlet */
	private LocaleResolver localeResolver;

	/** ThemeResolver used by this servlet */
	private ThemeResolver themeResolver;

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

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

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

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


	/**
	 * Set whether to perform cleanup of request attributes after an include request,
	 * i.e. whether to reset the original state of all request attributes after the
	 * DispatcherServlet has processed within an include request. Else, just the
	 * DispatcherServlet's own request attributes will be reset, but not model
	 * attributes for JSPs or special attributes set by views (for example, JSTL's).
	 * <p>Default is true, which is strongly recommended. Views should not rely on
	 * request attributes having been set by (dynamic) includes. This allows JSP views
	 * rendered by an included controller to use any model attributes, even with the
	 * same names as in the main JSP, without causing side effects. Only turn this
	 * off for special needs, for example to deliberately allow main JSPs to access
	 * attributes from JSP views rendered by an included controller.
	 */
	public void setCleanupAfterInclude(boolean cleanupAfterInclude) {
		this.cleanupAfterInclude = cleanupAfterInclude;
	}

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

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


	/**
	 * Overridden method, invoked after any bean properties have been set and the
	 * WebApplicationContext and BeanFactory for this namespace is available.
	 * <p>Loads HandlerMapping and HandlerAdapter objects, and configures a
	 * ViewResolver and a LocaleResolver.
	 */
	protected void initFrameworkServlet() throws ServletException, BeansException {
		initMultipartResolver();
		initLocaleResolver();
		initThemeResolver();
		initHandlerMappings();
		initHandlerAdapters();
		initHandlerExceptionResolvers();
		initViewResolvers();
	}

	/**