一、springMVC

1.1 springMVC的总体设计

springMVC源码下载：http://download.csdn.net/detail/yangchao13341408947/8905157

要使用springMVC，需要：

1）在web.xml文件中配置一个DispatcherServlet,如下<servlet>


   		
    
     springmvc
    		
    
     org.springframework.web.servlet.DispatcherServlet
    		
    			
     
      contextConfigLocation
     			
     
      classpath:springmvc-servlet.xml
     		
    		
    
     2
    	
   	
   		
    
     springmvc
    		
    
     /

2）定义一个springmvc-servlet.xml，定义Mapping、view、control

总结：springMVC的使用非常简单，我们只要扩展一个路径映射关系；定义一个试图解析器；再定义一个业务逻辑的处理流程规则，springMVC 就能够帮你完成所有的MVC功能了。

要搞清楚springMVC如何工作，主要看DispatcherServlet的代码与DispatcherServlet类相关的结构。

1.2 DispatcherServlet

1.2.1 DispatcherServlet 类图

DispatcherServlet-->FrameworkServlet-->HttpServletBean-->HttpServlet（-->表示继承）

DispatcherServlet 类继承了HttpServlet,在servlet的init方法调用时DispatcherServlet执行springMVC的初始化工作。可以在其initStrategies方法中知道：

protected void initStrategies(ApplicationContext context) {		initMultipartResolver(context);		initLocaleResolver(context);		initThemeResolver(context);		initHandlerMappings(context);		initHandlerAdapters(context);		initHandlerExceptionResolvers(context);		initRequestToViewNameTranslator(context);		initViewResolvers(context);		initFlashMapManager(context);	}

1） initMutipartResolver 用于处理文件上传

2）initLocaleResolver 用于处理国际化

3）initThemeResolver 用于定义一个主题

4） initHandlerMappings 定义用户设置的请求映射关系

5） initHandlerAdapters 根据handler的类型定义不同的处理规则

6）initHandlerExceptionResolvers 当handler出错时，会通过这个handler统一处理

7）initRequestToViewNameTranslator 将指定的viewname按照定义的requestToViewNameTranslator替换成想要的格式，如加上前缀或者后缀

8）initViewResolvers 将view解析成页面

9）initFlashMapManager ：Initialize the {@link FlashMapManager} used by this servlet instance.

1.2.2 DispatcherServlet启动都做了什么

在springMVC框架中，有3个组件是用户必须要定义和扩展的：定义URL映射规则、实现业务逻辑的handler实例对象、渲染模板资源。

HttpServlet 初始化时调用了HttpServletBean 的init方法：该方法的作用是获取servlet中的init参数，并创建一个beanwrapper对象，然后由子类真正执行beanwrapper的初始化工作，代码如下：

@Override	public final void init() throws ServletException {		if (logger.isDebugEnabled()) {			logger.debug("Initializing servlet '" + getServletName() + "'");		}		// Set bean properties from init parameters.		try {			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));			initBeanWrapper(bw);			bw.setPropertyValues(pvs, true);		}		catch (BeansException ex) {			logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);			throw ex;		}		// Let subclasses do whatever initialization they like.		initServletBean();		if (logger.isDebugEnabled()) {			logger.debug("Servlet '" + getServletName() + "' configured successfully");		}	}

但是HttpServletBean和DispatcherServlet都没有覆盖其initBeanWrapper(bw)方法，所以创建的BeanWrapper对象没有任何作用，spring容器也不是通过BeanWrapper创建的。

spring容器的创建是在FrameworkServlet类中的initServletBean（）方法中完成的，这个方法会创建WebApplicationContext 对象。

@Override	protected final void initServletBean() throws ServletException {		getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");		if (this.logger.isInfoEnabled()) {			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");		}		long startTime = System.currentTimeMillis();		try {			this.webApplicationContext = initWebApplicationContext();			initFrameworkServlet();		}		catch (ServletException ex) {			this.logger.error("Context initialization failed", ex);			throw ex;		}		catch (RuntimeException ex) {			this.logger.error("Context initialization failed", ex);			throw ex;		}		if (this.logger.isInfoEnabled()) {			long elapsedTime = System.currentTimeMillis() - startTime;			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +					elapsedTime + " ms");		}	}

spring容器的加载时会调用DispatcherServlet的initStrategies（）方法来完成DispatcherServlet中定义的初始化工作。在initStrategies（）方法中会初始化springMVC框架需要的8个组件，这个8个组件对应的8个bean对象都保存在DispatcherServlet类中。

1.3 control设计

springMVC的control主要由HandlerMapping和HandlerAdapters两个组件提供。HandlerMapping负责映射用户的URL和对应的处理类，HandlerAdapters并没有规定这个URL与应用的处理类如何映射，在HandlerMapping接口中只定义了根据一个URL必须返回一个由HandlerExecutionChain代表的处理链，我们可以在这个处理链中添加任意的HandlerAdapters实例来处理这个URL请求。

1.3.1 HandlerMapping 初始化

Spring MVC 本身提供了很多HandlerMapping的实现类，默认使用BeanNameUrlHandlerMapping。以SimpleUrlHandlerMapping为例看Spring MVC如何将请求的URL映射到我们定义的bean的。

package org.springframework.web.servlet;import javax.servlet.http.HttpServletRequest;public interface HandlerMapping {	String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";	String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";		String INTROSPECT_TYPE_LEVEL_MAPPING = HandlerMapping.class.getName() + ".introspectTypeLevelMapping";	String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";	String MATRIX_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".matrixVariables";	String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";	HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;}

package org.springframework.web.servlet.handler;import java.util.HashMap;import java.util.Map;import java.util.Properties;import org.springframework.beans.BeansException;import org.springframework.util.CollectionUtils;public class SimpleUrlHandlerMapping extends AbstractUrlHandlerMapping {	private final Map
   
     urlMap = new HashMap
    
     ();	public void setMappings(Properties mappings) {		CollectionUtils.mergePropertiesIntoMap(mappings, this.urlMap);	}	public void setUrlMap(Map
     
       urlMap) {		this.urlMap.putAll(urlMap);	}	public Map
      
        getUrlMap() {		return this.urlMap;	}	@Override	public void initApplicationContext() throws BeansException {		super.initApplicationContext();		registerHandlers(this.urlMap);	}	protected void registerHandlers(Map
       
         urlMap) throws BeansException {		if (urlMap.isEmpty()) {			logger.warn("Neither 'urlMap' nor 'mappings' set on SimpleUrlHandlerMapping");		}		else {			for (Map.Entry
        
          entry : urlMap.entrySet()) { String url = entry.getKey(); Object handler = entry.getValue(); // Prepend with slash if not already present. if (!url.startsWith("/")) { url = "/" + url; } // Remove whitespace from handler bean name. if (handler instanceof String) { handler = ((String) handler).trim(); } registerHandler(url, handler); } } }}

1.3.2 HandlerAdapter 初始化

package org.springframework.web.servlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public interface HandlerAdapter {	boolean supports(Object handler);	ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;	long getLastModified(HttpServletRequest request, Object handler);}

HandlerMapping可以完成URL和Handler（思考：这里的Handler是什么？）的映射关系，那么HandlerAdapter就可以帮助自定义各种Handler了。在springMVC中提供的三种典型的HandlerMapping实现类。

SimpleServletHandlerAdapter ：可以继承servlet接口

HttpRequestHandlerAdapter：可以继承HttpRequestHandler接口

SimpleControllerHandlerAdapter：可以继承controller接口

HandlerAdapter 的初始化：简单的创建一个HandlerAdapter对象，将这个对象保存在DispatcherServlet的HandlerAdapters集合中。当springMVC将某个URL对应到某个Handler时，在HandlerAdapters集合中查询那个HandlerAdapter接口对应的方法。

1.3.3 control的调用逻辑

整个springMVC的调用是从DispatcherServlet的doService()方法开始的，在doService方法中会将ApplicationContext、localResolver、themeResolver等对象添加到request中以便于在后面使用。接着调用doDispatch方法，这个方法是主要的处理用户请求的地方。

@Override	protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {		if (logger.isDebugEnabled()) {			String requestUri = urlPathHelper.getRequestUri(request);			String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";			logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed +					" processing " + request.getMethod() + " request for [" + requestUri + "]");		}		// Keep a snapshot of the request attributes in case of an include,		// to be able to restore the original attributes after the include.		Map
   
     attributesSnapshot = null;		if (WebUtils.isIncludeRequest(request)) {			logger.debug("Taking snapshot of request attributes before include");			attributesSnapshot = new HashMap
    
     ();			Enumeration
      attrNames = request.getAttributeNames();			while (attrNames.hasMoreElements()) {				String attrName = (String) attrNames.nextElement();				if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) {					attributesSnapshot.put(attrName, request.getAttribute(attrName));				}			}		}		// Make framework objects available to handlers and view objects.		request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());		request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);		request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);		request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());		FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);		if (inputFlashMap != null) {			request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));		}		request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());		request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);		try {			doDispatch(request, response);		}		finally {			if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {				return;			}			// Restore the original attribute snapshot, in case of an include.			if (attributesSnapshot != null) {				restoreAttributesAfterInclude(request, attributesSnapshot);			}		}	}

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {		HttpServletRequest processedRequest = request;		HandlerExecutionChain mappedHandler = null;		boolean multipartRequestParsed = false;		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);		try {			ModelAndView mv = null;			Exception dispatchException = null;			try {				processedRequest = checkMultipart(request);				multipartRequestParsed = processedRequest != request;				// Determine handler for the current request.				mappedHandler = getHandler(processedRequest);				if (mappedHandler == null || mappedHandler.getHandler() == null) {					noHandlerFound(processedRequest, response);					return;				}				// Determine handler adapter for the current request.				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());				// Process last-modified header, if supported by the handler.				String method = request.getMethod();				boolean isGet = "GET".equals(method);				if (isGet || "HEAD".equals(method)) {					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());					if (logger.isDebugEnabled()) {						String requestUri = urlPathHelper.getRequestUri(request);						logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);					}					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {						return;					}				}				if (!mappedHandler.applyPreHandle(processedRequest, response)) {					return;				}				try {					// Actually invoke the handler.					mv = ha.handle(processedRequest, response, mappedHandler.getHandler());				}				finally {					if (asyncManager.isConcurrentHandlingStarted()) {						return;					}				}				applyDefaultViewName(request, mv);				mappedHandler.applyPostHandle(processedRequest, response, mv);			}			catch (Exception ex) {				dispatchException = ex;			}			processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);		}		catch (Exception ex) {			triggerAfterCompletion(processedRequest, response, mappedHandler, ex);		}		catch (Error err) {			triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);		}		finally {			if (asyncManager.isConcurrentHandlingStarted()) {				// Instead of postHandle and afterCompletion				mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);				return;			}			// Clean up any resources used by a multipart request.			if (multipartRequestParsed) {				cleanupMultipart(processedRequest);			}		}	}

control处理的关键是DispatcherServlet的handlerMappings集合中根据请求的URL匹配每个HandlerMapping对象中的某个Handler,匹配成功返回这个Handler的处理链HandlerExecutionChain对象，这个HandlerExecutionChain对象中包含了多个HandlerInterceptor对象。HandlerInterceptor接口中定义的三个方法：preHandle和postHandle分别在Handler执行前和执行后执行，afterCompletion在view渲染完成、DispatcherServlet返回之前执行。

Q1:HandlerExecutionChain

参考：《深入分析javaweb技术内幕》——许立波，电子工业出版社

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