@Controllerpublic class FormAction{ // 这样的方法里，一般是用来注册一些PropertyEditor @InitBinder public void initBinder(WebDataBinder binder) throws Exception { DateFormat df = new SimpleDateFormat("yyyy---MM---dd HH:mm:ss"); CustomDateEditor dateEditor = new CustomDateEditor(df, true); binder.registerCustomEditor(Date.class, dateEditor); } @RequestMapping(value="/test/json",method=RequestMethod.GET) @ResponseBody public Map getFormData(Date date){ Map map=new HashMap (); map.put("name","lg"); map.put("age",23); map.put("date",new Date()); return map; }} xml文件仅仅开启mvc:ananotation-driven: 然后访问 http://localhost:8080/test/json?date=2014---08---3 03:34:23，便看到成功的获取到了数据。接下来源代码代码分析这一过程： 由于使用了@RequestMapping所以会选择RequestMappingHandlerAdapter来调度执行相应的方法，如下：
/** * Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView} * if view resolution is required. */ private ModelAndView invokeHandleMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ServletWebRequest webRequest = new ServletWebRequest(request, response);//我们关注的重点重点重点重点重点重点重点重点 WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod); ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory); ServletInvocableHandlerMethod requestMappingMethod = createRequestMappingMethod(handlerMethod, binderFactory); ModelAndViewContainer mavContainer = new ModelAndViewContainer(); mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request)); modelFactory.initModel(webRequest, mavContainer, requestMappingMethod); mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect); AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response); asyncWebRequest.setTimeout(this.asyncRequestTimeout); final WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); asyncManager.setTaskExecutor(this.taskExecutor); asyncManager.setAsyncWebRequest(asyncWebRequest); asyncManager.registerCallableInterceptors(this.callableInterceptors); asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors); if (asyncManager.hasConcurrentResult()) { Object result = asyncManager.getConcurrentResult(); mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0]; asyncManager.clearConcurrentResult(); if (logger.isDebugEnabled()) { logger.debug("Found concurrent result value [" + result + "]"); } requestMappingMethod = requestMappingMethod.wrapConcurrentResult(result); } requestMappingMethod.invokeAndHandle(webRequest, mavContainer); if (asyncManager.isConcurrentHandlingStarted()) { return null; } return getModelAndView(mavContainer, modelFactory, webRequest); } 这里面就是整个执行过程。首先绑定请求参数到方法的参数上，然后执行方法，接下来根据方法返回的类型来选择合适的HandlerMethodReturnValueHandler来进行处理，最后要么走view路线，要么直接写入response的body中返回。 我们此时关注的重点是：如何绑定请求参数到方法的参数上的呢？ WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod); 针对每次对该handlerMethod请求产生一个绑定工厂，由这个工厂来完成数据的绑定。 这里的handlerMethod包含了 controller对象FormAction和、test/json映射到的方法即getFormData。 然后详细看下getDataBinderFactory的实现： private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) throws Exception {//这里的handlerType便是controller的类型FormAction Class handlerType = handlerMethod.getBeanType(); Set methods = this.initBinderCache.get(handlerType); if (methods == null) {//关注点1：找出FormAction类的所有的含有@InitBinder的方法（方法的返回类型必须为void），找到后同时缓存起来 methods = HandlerMethodSelector.selectMethods(handlerType, INIT_BINDER_METHODS); this.initBinderCache.put(handlerType, methods); } List initBinderMethods = new ArrayList (); // Global methods first//关注点2：再寻找出全局的初始化Binder的方法 for (Entry > entry : this.initBinderAdviceCache .entrySet()) { if (entry.getKey().isApplicableToBeanType(handlerType)) { Object bean = entry.getKey().resolveBean(); for (Method method : entry.getValue()) { initBinderMethods.add(createInitBinderMethod(bean, method)); } } } for (Method method : methods) { Object bean = handlerMethod.getBean(); initBinderMethods.add(createInitBinderMethod(bean, method)); }//关注点3：找到了所有的与该handlerMethod有关的初始化binder的方法，保存起来 return createDataBinderFactory(initBinderMethods); } 上面稍微做了些注释，然后看下详细的内容： 关注点1：就是使用过滤，过滤类为：INIT_BINDER_METHODS，如下 /** * MethodFilter that matches {@link InitBinder @InitBinder} methods. */ public static final MethodFilter INIT_BINDER_METHODS = new MethodFilter() { @Override public boolean matches(Method method) { return AnnotationUtils.findAnnotation(method, InitBinder.class) != null; } }; 这个过滤类就是在handlerType即FormAction中过滤那些含有@InitBinder注解的方法。找到了之后就缓存起来，供下次使用。key为：handlerType，value为找到的方法。存至initBinderCache中。 关注点2：从initBinderAdviceCache中获取所有支持这个handlerType的method。这一块有待继续研究，这个initBinderAdviceCache是如何初始化来的等等。针对目前的工程来说，initBinderAdviceCache是为空的。 关注点3：遍历所有找到的和handlerType有关的method,然后封装成InvocableHandlerMethod，如下： for (Method method : methods) { Object bean = handlerMethod.getBean(); initBinderMethods.add(createInitBinderMethod(bean, method)); } private InvocableHandlerMethod createInitBinderMethod(Object bean, Method method) { InvocableHandlerMethod binderMethod = new InvocableHandlerMethod(bean, method); binderMethod.setHandlerMethodArgumentResolvers(this.initBinderArgumentResolvers); binderMethod.setDataBinderFactory(new DefaultDataBinderFactory(this.webBindingInitializer)); binderMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer); return binderMethod; } 在封装的过程中，同时设置一些RequestMappingHandlerAdapter的一些参数进去initBinderArgumentResolvers、webBindingInitializer、parameterNameDiscoverer。 封装完所有的方法后，创建出最终的WebDataBinderFactory。如下： protected InitBinderDataBinderFactory createDataBinderFactory(ListgetWebBindingInitializer()也是RequestMappingHandlerAdapter的webBindingInitializer参数。 至此绑定数据的工厂完成了，包含了这个handlerType的所有的PropertyEditor。这是准备工作，然后就是等待执行这个我们自己的方法getFormData执行时来完成参数的绑定过程。 绑定参数过程即getFormData的执行过程如下：binderMethods) throws Exception { return new ServletRequestDataBinderFactory(binderMethods, getWebBindingInitializer()); }
ServletInvocableHandlerMethod requestMappingMethod = createRequestMappingMethod(handlerMethod, binderFactory);略requestMappingMethod.invokeAndHandle(webRequest, mavContainer);其中的requestMappingMethod经过了进一步的包装，已经包含刚才已经创建的绑定工厂。 执行过程如下：
public final Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs); if (logger.isTraceEnabled()) { StringBuilder sb = new StringBuilder("Invoking ["); sb.append(getBeanType().getSimpleName()).append("."); sb.append(getMethod().getName()).append("] method with arguments "); sb.append(Arrays.asList(args)); logger.trace(sb.toString()); } Object returnValue = invoke(args); if (logger.isTraceEnabled()) { logger.trace("Method [" + getMethod().getName() + "] returned [" + returnValue + "]"); } return returnValue; } 分两大步，绑定参数和执行方法体。最重要的就是如何来绑定参数呢？ private Object[] getMethodArgumentValues(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { MethodParameter[] parameters = getMethodParameters(); Object[] args = new Object[parameters.length]; for (int i = 0; i < parameters.length; i++) { MethodParameter parameter = parameters[i]; parameter.initParameterNameDiscovery(this.parameterNameDiscoverer); GenericTypeResolver.resolveParameterType(parameter, getBean().getClass()); args[i] = resolveProvidedArgument(parameter, providedArgs); if (args[i] != null) { continue; } if (this.argumentResolvers.supportsParameter(parameter)) { try { args[i] = this.argumentResolvers.resolveArgument( parameter, mavContainer, request, this.dataBinderFactory); continue; } catch (Exception ex) { if (logger.isTraceEnabled()) { logger.trace(getArgumentResolutionErrorMessage("Error resolving argument", i), ex); } throw ex; } } if (args[i] == null) { String msg = getArgumentResolutionErrorMessage("No suitable resolver for argument", i); throw new IllegalStateException(msg); } } return args; } 绑定参数又引出来另一个重要名词：HandlerMethodArgumentResolver。args[i] = this.argumentResolvers.resolveArgument( parameter, mavContainer, request, this.dataBinderFactory);的具体内容如下： /** * Iterate over registered {@link HandlerMethodArgumentResolver}s and invoke the one that supports it. * @exception IllegalStateException if no suitable {@link HandlerMethodArgumentResolver} is found. */ @Override public Object resolveArgument( MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter); Assert.notNull(resolver, "Unknown parameter type [" + parameter.getParameterType().getName() + "]"); return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory); } 遍历所有已注册的HandlerMethodArgumentResolver，然后找出一个适合的来进行参数绑定，对于本工程来说，getFormData(Date date)的参数date默认是request params级别的，所以使用RequestParamMethodArgumentResolver来处理这一过程。处理过程如下： @Override public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { Class paramType = parameter.getParameterType(); NamedValueInfo namedValueInfo = getNamedValueInfo(parameter); Object arg = resolveName(namedValueInfo.name, parameter, webRequest); if (arg == null) { if (namedValueInfo.defaultValue != null) { arg = resolveDefaultValue(namedValueInfo.defaultValue); } else if (namedValueInfo.required) { handleMissingValue(namedValueInfo.name, parameter); } arg = handleNullValue(namedValueInfo.name, arg, paramType); } else if ("".equals(arg) && (namedValueInfo.defaultValue != null)) { arg = resolveDefaultValue(namedValueInfo.defaultValue); } if (binderFactory != null) { WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name); arg = binder.convertIfNecessary(arg, paramType, parameter); } handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest); return arg; } NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);获取参数信息，就是按照@RequestParam的3个属性来收集的，即defaultValue=null、required=false、name=date, Object arg = resolveName(namedValueInfo.name, parameter, webRequest);然后就是获取原始数据,获取过程如下： @Override protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest webRequest) throws Exception { Object arg; HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class); MultipartHttpServletRequest multipartRequest = WebUtils.getNativeRequest(servletRequest, MultipartHttpServletRequest.class); if (MultipartFile.class.equals(parameter.getParameterType())) { assertIsMultipartRequest(servletRequest); Assert.notNull(multipartRequest, "Expected MultipartHttpServletRequest: is a MultipartResolver configured?"); arg = multipartRequest.getFile(name); } else if (isMultipartFileCollection(parameter)) { assertIsMultipartRequest(servletRequest); Assert.notNull(multipartRequest, "Expected MultipartHttpServletRequest: is a MultipartResolver configured?"); arg = multipartRequest.getFiles(name); } else if(isMultipartFileArray(parameter)) { assertIsMultipartRequest(servletRequest); Assert.notNull(multipartRequest, "Expected MultipartHttpServletRequest: is a MultipartResolver configured?"); arg = multipartRequest.getFiles(name).toArray(new MultipartFile[0]); } else if ("javax.servlet.http.Part".equals(parameter.getParameterType().getName())) { assertIsMultipartRequest(servletRequest); arg = servletRequest.getPart(name); } else if (isPartCollection(parameter)) { assertIsMultipartRequest(servletRequest); arg = new ArrayList 通过webRequest.getParameterValues(name)来获取原始的字符串。这里便有涉及到了容器如tomcat的处理过程，这一获取参数的过程在本系列的第五篇文章tomcat的获取参数中进行了详细的源码介绍，那一篇主要是介绍乱码的。本文章不再介绍，接着说，这样就可以获取到我们请求的原始字符串"2014---08---3 03:34:23"，接下来便是执行转换绑定的过程： if (binderFactory != null) { WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name); arg = binder.convertIfNecessary(arg, paramType, parameter); } 这一过程就是要寻找我们已经注册的所有的PropertyEditor来进行转换，如果还没有找到，则使用另一套转换流程，使用conversionService来进行转换。我们慢慢来看这一过程，有了binderFactory便可以创建出WebDataBinder，具体的创建过程如下： public final WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName) throws Exception { WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest); if (this.initializer != null) { this.initializer.initBinder(dataBinder, webRequest); } initBinder(dataBinder, webRequest); return dataBinder; } 先创建出WebDataBinder，然后使用initializer的initBinder方法来初始化一些PropertyEditor，initializer的类型为我们常见的ConfigurableWebBindingInitializer即在mvc:annotation-driven时默认注册的最终设置为RequestMappingHandlerAdapter的webBindingInitializer属性值。this.initializer.initBinder(dataBinder, webRequest);过程如下： @Override public void initBinder(WebDataBinder binder, WebRequest request) { binder.setAutoGrowNestedPaths(this.autoGrowNestedPaths); if (this.directFieldAccess) { binder.initDirectFieldAccess(); } if (this.messageCodesResolver != null) { binder.setMessageCodesResolver(this.messageCodesResolver); } if (this.bindingErrorProcessor != null) { binder.setBindingErrorProcessor(this.bindingErrorProcessor); } if (this.validator != null && binder.getTarget() != null && this.validator.supports(binder.getTarget().getClass())) { binder.setValidator(this.validator); } if (this.conversionService != null) { binder.setConversionService(this.conversionService); } if (this.propertyEditorRegistrars != null) { for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) { propertyEditorRegistrar.registerCustomEditors(binder); } } } 即设置一些我们conversionService、messageCodesResolver、validator 等，这些参数即我们在mvc:annotation中进行设置的，若无设置，采用默认的。 继续执行initBinder(dataBinder, webRequest); public void initBinder(WebDataBinder binder, NativeWebRequest request) throws Exception { for (InvocableHandlerMethod binderMethod : this.binderMethods) { if (isBinderMethodApplicable(binderMethod, binder)) { Object returnValue = binderMethod.invokeForRequest(request, null, binder); if (returnValue != null) { throw new IllegalStateException("@InitBinder methods should return void: " + binderMethod); } } } } 执行那些适合我们已经创建的WebDataBinder，怎样才叫适合的呢？看isBinderMethodApplicable(binderMethod, binder)方法 protected boolean isBinderMethodApplicable(HandlerMethod initBinderMethod, WebDataBinder binder) { InitBinder annot = initBinderMethod.getMethodAnnotation(InitBinder.class); Collection names = Arrays.asList(annot.value()); return (names.size() == 0 || names.contains(binder.getObjectName())); } 当initBinderMethod上的@InitBinder注解指定了value，该value可以是多个，当它包含了我们的方法的参数date,则这个initBinderMethod就会被执行。当@InitBinder注解没有指定value，则也会被执行。所以为了不用执行一些不必要的initBinderMethod，我们最好为这些initBinderMethod上的@InitBinder加上value限定。对于我们写的initBinder便因此开始执行了。 由binderFactory创建出来的WebDataBinder就此完成，然后才是详细的转换过程： public这里首先使用已注册的PropertyEditor，当仍然没有找到时才使用ConversionService。对于本工程来说，由于已经手动注册了对于Date的转换的PropertyEditor即CustomDateEditor，然后便会执行CustomDateEditor的具体的转换过程。至此，大体过程就算是完了。T convertIfNecessary(String propertyName, Object oldValue, Object newValue, Class requiredType, TypeDescriptor typeDescriptor) throws IllegalArgumentException { Object convertedValue = newValue; // Custom editor for this type? PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName); ConversionFailedException firstAttemptEx = null; // No custom editor but custom ConversionService specified? ConversionService conversionService = this.propertyEditorRegistry.getConversionService(); //略}