SPRING MVC源码解析

DispatcherServlet extends FrameworkServlet extends HttpServletBean extends HttpServletBean extends HttpServlet

服务方法 请求的第一个方法

/**
	 * Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}
	 * for the actual dispatching.
	 */
	@Override
	protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
		if (logger.isDebugEnabled()) {
			String requestUri = urlPathHelper.getRequestUri(request);
			logger.debug("DispatcherServlet with name '" + getServletName() + "' 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<String, Object> attributesSnapshot = null;
		if (WebUtils.isIncludeRequest(request)) {
			logger.debug("Taking snapshot of request attributes before include");
			attributesSnapshot = new HashMap<String, Object>();
			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());

		try {
			[u][b]doDispatch(request, response);[/b][/u]		}
		finally {
			// Restore the original attribute snapshot, in case of an include.
			if (attributesSnapshot != null) {
				restoreAttributesAfterInclude(request, attributesSnapshot);
			}
		}
	}

Process the actual dispatching to the handler
本次请求实际的请求方法

	/**
	 * Process the actual dispatching to the handler.
	 * <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
	 * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
	 * to find the first that supports the handler class.
	 * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
	 * themselves to decide which methods are acceptable.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws Exception in case of any kind of processing failure
	 */
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HttpServletRequest processedRequest = request;
		HandlerExecutionChain mappedHandler = null;
		int interceptorIndex = -1;

		try {
			ModelAndView mv;
			boolean errorView = false;

			try {
				processedRequest = checkMultipart(request);

				// Determine handler for the current request.
				mappedHandler = getHandler(processedRequest, false);
				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);
					}
//如果是get请求则判断是否有客户端缓存
					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}

				// Apply preHandle methods of registered interceptors.
				HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
				if (interceptors != null) {
					for (int i = 0; i < interceptors.length; i++) {
						HandlerInterceptor interceptor = interceptors[i];
						if (!interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())) {
							triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
							return;
						}
						interceptorIndex = i;
					}
				}
//实际请求方法
				// Actually invoke the handler.
				mv =[b] ha.handle(processedRequest, response, mappedHandler.getHandler());[/b]
				// Do we need view name translation?
				if (mv != null && !mv.hasView()) {
					mv.setViewName(getDefaultViewName(request));
				}

				// Apply postHandle methods of registered interceptors.
				if (interceptors != null) {
					for (int i = interceptors.length - 1; i >= 0; i--) {
						HandlerInterceptor interceptor = interceptors[i];
						interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);
					}
				}
			}
			catch (ModelAndViewDefiningException ex) {
				logger.debug("ModelAndViewDefiningException encountered", ex);
				mv = ex.getModelAndView();
			}
			catch (Exception ex) {
				Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
				mv = processHandlerException(processedRequest, response, handler, ex);
				errorView = (mv != null);
			}

			// Did the handler return a view to render?
			if (mv != null && !mv.wasCleared()) {
				render(mv, processedRequest, response);
				if (errorView) {
					WebUtils.clearErrorRequestAttributes(request);
				}
			}
			else {
				if (logger.isDebugEnabled()) {
					logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
							"': assuming HandlerAdapter completed request handling");
				}
			}

			// Trigger after-completion for successful outcome.
			triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
		}

		catch (Exception ex) {
			// Trigger after-completion for thrown exception.
			triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
			throw ex;
		}
		catch (Error err) {
			ServletException ex = new NestedServletException("Handler processing failed", err);
			// Trigger after-completion for thrown exception.
			triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
			throw ex;
		}

		finally {
			// Clean up any resources used by a multipart request.
			if (processedRequest != request) {
				cleanupMultipart(processedRequest);
			}
		}
	}

4个实现类



//AnnotationMethodHandlerAdapter 注解实现类

public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		Class<?> clazz = ClassUtils.getUserClass(handler);
		Boolean annotatedWithSessionAttributes = this.sessionAnnotatedClassesCache.get(clazz);
		if (annotatedWithSessionAttributes == null) {
			annotatedWithSessionAttributes = (AnnotationUtils.findAnnotation(clazz, SessionAttributes.class) != null);
			this.sessionAnnotatedClassesCache.put(clazz, annotatedWithSessionAttributes);
		}

		if (annotatedWithSessionAttributes) {
			// Always prevent caching in case of session attribute management.
			checkAndPrepare(request, response, this.cacheSecondsForSessionAttributeHandlers, true);
			// Prepare cached set of session attributes names.
		}
		else {
			// Uses configured default cacheSeconds setting.
			checkAndPrepare(request, response, true);
		}

		// Execute invokeHandlerMethod in synchronized block if required.
		if (this.synchronizeOnSession) {
			HttpSession session = request.getSession(false);
			if (session != null) {
				Object mutex = WebUtils.getSessionMutex(session);
				synchronized (mutex) {
					return invokeHandlerMethod(request, response, handler);
				}
			}
		}

		[b]return invokeHandlerMethod(request, response, handler);[/b]	}




protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {
//handler方法解析器
		ServletHandlerMethodResolver methodResolver = getMethodResolver(handler);
//handler方法
		Method handlerMethod = methodResolver.resolveHandlerMethod(request);
//handler方法的执行器
		ServletHandlerMethodInvoker methodInvoker = new ServletHandlerMethodInvoker(methodResolver);

		ServletWebRequest webRequest = new ServletWebRequest(request, response);
//上下文map对象 request 及session中的Attribute
		ExtendedModelMap implicitModel = new BindingAwareModelMap();
//执行handler方法
		Object [b]result [/b]= methodInvoker.invokeHandlerMethod(handlerMethod, handler, webRequest, implicitModel);
//将执行结果转化的为modelAndView对象
		ModelAndView mav =
				methodInvoker.getModelAndView(handlerMethod, handler.getClass(), [b]result[/b], implicitModel, webRequest);
//将当前上下文的内容更新到modelView对象中
		methodInvoker.updateModelAttributes(handler, (mav != null ? mav.getModel() : null), implicitModel, webRequest);
		return mav;
	}

执行handler 方法

public final Object invokeHandlerMethod(Method handlerMethod, Object handler,
			NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception {

		Method handlerMethodToInvoke = BridgeMethodResolver.findBridgedMethod(handlerMethod);
		try {
			boolean debug = logger.isDebugEnabled();
//将ssesion中的内容加入到	implicitModel		
for (String attrName : this.methodResolver.getActualSessionAttributeNames()) {
				Object attrValue = this.sessionAttributeStore.retrieveAttribute(webRequest, attrName);
				if (attrValue != null) {
					implicitModel.addAttribute(attrName, attrValue);
				}
			}
/*先执行ModelAttributeMethods暴露表单引用对象为模型数据：放在处理器的一般方法（非功能处理方法）上时，是为表单准备要展示的表单引用对象，如注册时需要选择的所在城市等，而且在执行功能处理方法（@RequestMapping注解的方法）之前，自动添加到模型对象中，用于视图页面展示时使用

/**
 * Annotation that binds a method parameter or method return value
 * to a named model attribute, exposed to a web view. Supported
 * for {@link RequestMapping} annotated handler classes.
 *
 * <p>Can be used to expose command objects to a web view, using
 * specific attribute names, through annotating corresponding
 * parameters of a {@link RequestMapping} annotated handler method).
 *
 * <p>Can also be used to expose reference data to a web view
 * through annotating accessor methods in a controller class which
 * is based on {@link RequestMapping} annotated handler methods,
 * with such accessor methods allowed to have any arguments that
 * {@link RequestMapping} supports for handler methods, returning
 * the model attribute value to expose.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
@Target({ElementType.PARAMETER, ElementType.METHOD})
//该注解可以注解在方法或参数上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ModelAttribute {

	/**
	 * The name of the model attribute to bind to.
	 * <p>The default model attribute name is inferred from the declared
	 * attribute type (i.e. the method parameter type or method return type),
	 * based on the non-qualified class name:
	 * e.g. "orderAddress" for class "mypackage.OrderAddress",
	 * or "orderAddressList" for "List&lt;mypackage.OrderAddress&gt;".
	 */
	String value() default "";

}
*/


//该注解在方法上

			for (Method attributeMethod : this.methodResolver.getModelAttributeMethods()) {
				Method attributeMethodToInvoke = BridgeMethodResolver.findBridgedMethod(attributeMethod);
				Object[] args = [b]resolveHandlerArguments(attributeMethodToInvoke, handler, webRequest, implicitModel);[/b]				if (debug) {
					logger.debug("Invoking model attribute method: " + attributeMethodToInvoke);
				}
				String attrName = AnnotationUtils.findAnnotation(attributeMethod, ModelAttribute.class).value();
				if (!"".equals(attrName) && implicitModel.containsAttribute(attrName)) {
					continue;
				}
				ReflectionUtils.makeAccessible(attributeMethodToInvoke);
				Object attrValue = attributeMethodToInvoke.invoke(handler, args);
				if ("".equals(attrName)) {
					Class resolvedType = GenericTypeResolver.resolveReturnType(attributeMethodToInvoke, handler.getClass());
					attrName = Conventions.getVariableNameForReturnType(attributeMethodToInvoke, resolvedType, attrValue);
				}
				if (!implicitModel.containsAttribute(attrName)) {
					implicitModel.addAttribute(attrName, attrValue);
				}
			}
			Object[] args = resolveHandlerArguments(handlerMethodToInvoke, handler, webRequest, implicitModel);
			if (debug) {
				logger.debug("Invoking request handler method: " + handlerMethodToInvoke);
			}
			ReflectionUtils.makeAccessible(handlerMethodToInvoke);
//执行请求方法
			return handlerMethodToInvoke.invoke(handler, args);
		}
		catch (IllegalStateException ex) {
			// Internal assertion failed (e.g. invalid signature):
			// throw exception with full handler method context...
			throw new HandlerMethodInvocationException(handlerMethodToInvoke, ex);
		}
		catch (InvocationTargetException ex) {
			// User-defined @ModelAttribute/@InitBinder/@RequestMapping method threw an exception...
			ReflectionUtils.rethrowException(ex.getTargetException());
			return null;
		}
	}

获取反射执行方法所需要的参数

private Object[] resolveHandlerArguments(Method handlerMethod, Object handler,
			NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception {

		Class[] paramTypes = handlerMethod.getParameterTypes();
		Object[] args = new Object[paramTypes.length];

		for (int i = 0; i < args.length; i++) {
			MethodParameter methodParam = new MethodParameter(handlerMethod, i);
			methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer);
			GenericTypeResolver.resolveParameterType(methodParam, handler.getClass());
			String paramName = null;
			String headerName = null;
			boolean requestBodyFound = false;
			String cookieName = null;
			String pathVarName = null;
			String attrName = null;
			boolean required = false;
			String defaultValue = null;
			boolean validate = false;
			int annotationsFound = 0;
			Annotation[] paramAnns = methodParam.getParameterAnnotations();

			for (Annotation paramAnn : paramAnns) {
				if (RequestParam.class.isInstance(paramAnn)) {
					RequestParam requestParam = (RequestParam) paramAnn;
					paramName = requestParam.value();
					required = requestParam.required();
					defaultValue = parseDefaultValueAttribute(requestParam.defaultValue());
					annotationsFound++;
				}
				else if (RequestHeader.class.isInstance(paramAnn)) {
					RequestHeader requestHeader = (RequestHeader) paramAnn;
					headerName = requestHeader.value();
					required = requestHeader.required();
					defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue());
					annotationsFound++;
				}
				else if (RequestBody.class.isInstance(paramAnn)) {
					requestBodyFound = true;
					annotationsFound++;
				}
				else if (CookieValue.class.isInstance(paramAnn)) {
					CookieValue cookieValue = (CookieValue) paramAnn;
					cookieName = cookieValue.value();
					required = cookieValue.required();
					defaultValue = parseDefaultValueAttribute(cookieValue.defaultValue());
					annotationsFound++;
				}
				else if (PathVariable.class.isInstance(paramAnn)) {
					PathVariable pathVar = (PathVariable) paramAnn;
					pathVarName = pathVar.value();
					annotationsFound++;
				}
//这里是参数类型 该注解在参数上
				else if (ModelAttribute.class.isInstance(paramAnn)) {
					ModelAttribute attr = (ModelAttribute) paramAnn;
					attrName = attr.value();
					annotationsFound++;
				}
				else if (Value.class.isInstance(paramAnn)) {
					defaultValue = ((Value) paramAnn).value();
				}
				else if ("Valid".equals(paramAnn.annotationType().getSimpleName())) {
					validate = true;
				}
			}

			if (annotationsFound > 1) {
				throw new IllegalStateException("Handler parameter annotations are exclusive choices - " +
						"do not specify more than one such annotation on the same parameter: " + handlerMethod);
			}

			if (annotationsFound == 0) {
				Object argValue = resolveCommonArgument(methodParam, webRequest);
				if (argValue != WebArgumentResolver.UNRESOLVED) {
					args[i] = argValue;
				}
				else if (defaultValue != null) {
					args[i] = resolveDefaultValue(defaultValue);
				}
				else {
					Class paramType = methodParam.getParameterType();
					if (Model.class.isAssignableFrom(paramType) || Map.class.isAssignableFrom(paramType)) {
						args[i] = implicitModel;
					}
					else if (SessionStatus.class.isAssignableFrom(paramType)) {
						args[i] = this.sessionStatus;
					}
					else if (HttpEntity.class.isAssignableFrom(paramType)) {
						args[i] = resolveHttpEntityRequest(methodParam, webRequest);
					}
					else if (Errors.class.isAssignableFrom(paramType)) {
						throw new IllegalStateException("Errors/BindingResult argument declared " +
								"without preceding model attribute. Check your handler method signature!");
					}
					else if (BeanUtils.isSimpleProperty(paramType)) {
						paramName = "";
					}
					else {
						attrName = "";
					}
				}
			}

			if (paramName != null) {
				args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler);
			}
			else if (headerName != null) {
				args[i] = resolveRequestHeader(headerName, required, defaultValue, methodParam, webRequest, handler);
			}
			else if (requestBodyFound) {
				args[i] = resolveRequestBody(methodParam, webRequest, handler);
			}
			else if (cookieName != null) {
				args[i] = resolveCookieValue(cookieName, required, defaultValue, methodParam, webRequest, handler);
			}
			else if (pathVarName != null) {
				args[i] = resolvePathVariable(pathVarName, methodParam, webRequest, handler);
			}
//struts 2的模型驱动
			else if (attrName != null) {
				WebDataBinder binder =
						resolveModelAttribute(attrName, methodParam, implicitModel, webRequest, handler);
				boolean assignBindingResult = (args.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1]));
				if (binder.getTarget() != null) {
					doBind(binder, webRequest, validate, !assignBindingResult);
				}
				args[i] = binder.getTarget();
				if (assignBindingResult) {
					args[i + 1] = binder.getBindingResult();
					i++;
				}
				implicitModel.putAll(binder.getBindingResult().getModel());
			}
		}

		return args;
	}

//模型注入

private WebDataBinder resolveModelAttribute(String attrName, MethodParameter methodParam,
			ExtendedModelMap implicitModel, NativeWebRequest webRequest, Object handler) throws Exception {

		// Bind request parameter onto object...
		String name = attrName;
		if ("".equals(name)) {
			name = Conventions.getVariableNameForParameter(methodParam);
		}
		Class<?> paramType = methodParam.getParameterType();
		Object bindObject;
		if (implicitModel.containsKey(name)) {
			bindObject = implicitModel.get(name);
		}
		else if (this.methodResolver.isSessionAttribute(name, paramType)) {
			bindObject = this.sessionAttributeStore.retrieveAttribute(webRequest, name);
			if (bindObject == null) {
				raiseSessionRequiredException("Session attribute '" + name + "' required - not found in session");
			}
		}
		else {
			bindObject = BeanUtils.instantiateClass(paramType);
		}
		WebDataBinder binder = createBinder(webRequest, bindObject, name);
		initBinder(handler, name, binder, webRequest);
		return binder;
	}


	protected void initBinder(Object handler, String attrName, WebDataBinder binder, NativeWebRequest webRequest)
			throws Exception {

		if (this.bindingInitializer != null) {
			this.bindingInitializer.initBinder(binder, webRequest);
		}
		if (handler != null) {
			Set<Method> initBinderMethods = this.methodResolver.getInitBinderMethods();
			if (!initBinderMethods.isEmpty()) {
				boolean debug = logger.isDebugEnabled();
				for (Method initBinderMethod : initBinderMethods) {
					Method methodToInvoke = BridgeMethodResolver.findBridgedMethod(initBinderMethod);
					String[] targetNames = AnnotationUtils.findAnnotation(initBinderMethod, InitBinder.class).value();
					if (targetNames.length == 0 || Arrays.asList(targetNames).contains(attrName)) {
						Object[] initBinderArgs =
								resolveInitBinderArguments(handler, methodToInvoke, binder, webRequest);
						if (debug) {
							logger.debug("Invoking init-binder method: " + methodToInvoke);
						}
						ReflectionUtils.makeAccessible(methodToInvoke);
						Object returnValue = methodToInvoke.invoke(handler, initBinderArgs);
						if (returnValue != null) {
							throw new IllegalStateException(
									"InitBinder methods must not have a return value: " + methodToInvoke);
						}
					}
				}
			}
		}
	}