SpringBoot项目中什么情况下需要添加@ResponseBody注解

  @ApiOperation(value="分页查询")
  @RequestMapping(value = "/listPage",method = RequestMethod.POST)
  @ResponseBody
  public ResponseBean listPage(@RequestBody JSONObject params){
    Integer pageNum = params.getInteger("pageNum");
    Integer pageSize = params.getInteger("pageSize");
    String vagueParam = params.getString("vagueParam");
    IPage<TbSysGoodsCategory> indexPage = new Page<>(pageNum, pageSize);
    QueryWrapper<TbSysGoodsCategory> queryWrapper = new QueryWrapper<>();
    if (!StringUtils.isEmpty(vagueParam)){
      queryWrapper.like("name",vagueParam).or().like("code",vagueParam);
    }
    //排序
    queryWrapper.orderByDesc("id");
    indexPage = tbSysGoodsCategoryService.page(indexPage,queryWrapper);
    return new ResponseBean<>(true, indexPage, CommonEnum.SUCCESS_OPTION);
  }

@Override
@Nullable
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
		throws Exception {

	return handleInternal(request, response, (HandlerMethod) handler);
}

//1.检测请求方法是否支持；
//2.检测是否需要session但是没有获取到
	protected final void checkRequest(HttpServletRequest request) throws ServletException {
		// Check whether we should support the request method.
		String method = request.getMethod();
		if (this.supportedMethods != null && !this.supportedMethods.contains(method)) {
			throw new HttpRequestMethodNotSupportedException(method, this.supportedMethods);
		}

		// Check whether a session is required.
		if (this.requireSession && request.getSession(false) == null) {
			throw new HttpSessionRequiredException("Pre-existing session required but none found");
		}
	}

 @Nullable
  protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
  // 对应 2 
    ServletWebRequest webRequest = new ServletWebRequest(request, response);

    Object result;
    try {
// 对应 3
      WebDataBinderFactory binderFactory = this.getDataBinderFactory(handlerMethod);
  // 对应 4
      ModelFactory modelFactory = this.getModelFactory(handlerMethod, binderFactory);
  // 对应 5
      ServletInvocableHandlerMethod invocableMethod = this.createInvocableHandlerMethod(handlerMethod);
      if (this.argumentResolvers != null) {
        invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
      }

      if (this.returnValueHandlers != null) {
        invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
      }

      invocableMethod.setDataBinderFactory(binderFactory);
      invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
 // 对应 6
      ModelAndViewContainer mavContainer = new ModelAndViewContainer();
      mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
      modelFactory.initModel(webRequest, mavContainer, invocableMethod);
      mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
//对应 7
      AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
      asyncWebRequest.setTimeout(this.asyncRequestTimeout);
      WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
      asyncManager.setTaskExecutor(this.taskExecutor);
      asyncManager.setAsyncWebRequest(asyncWebRequest);
      asyncManager.registerCallableInterceptors(this.callableInterceptors);
      asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);
      if (asyncManager.hasConcurrentResult()) {
        result = asyncManager.getConcurrentResult();
        mavContainer = (ModelAndViewContainer)asyncManager.getConcurrentResultContext()[0];
        asyncManager.clearConcurrentResult();
        LogFormatUtils.traceDebug(this.logger, (traceOn) -> {
          String formatted = LogFormatUtils.formatValue(result, !traceOn);
          return "Resume with async result [" + formatted + "]";
        });
        invocableMethod = invocableMethod.wrapConcurrentResult(result);
      }
//这里会跳到【3】ServletInvocableHandlerMethod.invokeAndHandle
      invocableMethod.invokeAndHandle(webRequest, mavContainer, new Object[0]);
      
      if (!asyncManager.isConcurrentHandlingStarted()) {
//这里会跳到【4】RequestMappingHandlerAdapter.getModelAndView
        ModelAndView var15 = this.getModelAndView(mavContainer, modelFactory, webRequest);
        return var15;
      }

      result = null;
    } finally {
    //这里会跳到【5】ServletWebRequest.requestCompleted
      webRequest.requestCompleted();
    }

    return (ModelAndView)result;
  }

WebDataBinderFactory binderFactory = this.getDataBinderFactory(handlerMethod);

private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) throws Exception {
//获取handlerType 
		Class<&#63;> handlerType = handlerMethod.getBeanType();
		//根据handlerType 从initBinderCache获取到@InitBinder注解的方法
		Set<Method> methods = this.initBinderCache.get(handlerType);
		//如果initBinderCache中没有，就从handlerType查找@InitBinder注解的方法
		if (methods == null) {
			methods = MethodIntrospector.selectMethods(handlerType, INIT_BINDER_METHODS);
			this.initBinderCache.put(handlerType, methods);
		}
		List<InvocableHandlerMethod> initBinderMethods = new ArrayList<>();
		//遍历controllerAdviceBean的方法列表，从适合handlerType中拿到其方法列表
		//然后封装为一个个InvocableHandlerMethod放到initBinderMethods中
		// Global methods first
		this.initBinderAdviceCache.forEach((controllerAdviceBean, methodSet) -> {
			if (controllerAdviceBean.isApplicableToBeanType(handlerType)) {
				Object bean = controllerAdviceBean.resolveBean();
				for (Method method : methodSet) {
					initBinderMethods.add(createInitBinderMethod(bean, method));
				}
			}
		});
		for (Method method : methods) {
			Object bean = handlerMethod.getBean();
			initBinderMethods.add(createInitBinderMethod(bean, method));
		}
		return createDataBinderFactory(initBinderMethods);
	}

protected InitBinderDataBinderFactory createDataBinderFactory(List<InvocableHandlerMethod> binderMethods)
			throws Exception {
		return new ServletRequestDataBinderFactory(binderMethods, getWebBindingInitializer());
}

ModelFactory modelFactory = this.getModelFactory(handlerMethod, binderFactory);

private ModelFactory getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory) {
//获取当前handlerMethod对应的handlerType的SessionAttributesHandler 
//--如果没有就创建一个new SessionAttributesHandler(handlerType, this.sessionAttributeStore)
//参考④-①
		SessionAttributesHandler sessionAttrHandler = getSessionAttributesHandler(handlerMethod);
//获取handlerType 
		Class<&#63;> handlerType = handlerMethod.getBeanType();
//获取添加了@ModelAttribute注解的方法		
		Set<Method> methods = this.modelAttributeCache.get(handlerType);
		if (methods == null) {
			methods = MethodIntrospector.selectMethods(handlerType, MODEL_ATTRIBUTE_METHODS);
			this.modelAttributeCache.put(handlerType, methods);
		}
		List<InvocableHandlerMethod> attrMethods = new ArrayList<>();
//从controllerAdviceBean中获取适合当前handlerType的method，
//并封装为一个个InvocableHandlerMethod然后添加到attrMethods
		// Global methods first
		this.modelAttributeAdviceCache.forEach((controllerAdviceBean, methodSet) -> {
			if (controllerAdviceBean.isApplicableToBeanType(handlerType)) {
				Object bean = controllerAdviceBean.resolveBean();
				for (Method method : methodSet) {
					attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
				}
			}
		});
//遍历methods并封装为一个个InvocableHandlerMethod然后添加到attrMethods
		for (Method method : methods) {
			Object bean = handlerMethod.getBean();
			attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
		}
//根据attrMethods, binderFactory, sessionAttrHandler创建一个ModelFactory对象
		return new ModelFactory(attrMethods, binderFactory, sessionAttrHandler);
	}

private ModelFactory getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory) {
//获取当前handlerMethod对应的handlerType的SessionAttributesHandler 
//--如果没有就创建一个new SessionAttributesHandler(handlerType, this.sessionAttributeStore)
//参考④-①
		SessionAttributesHandler sessionAttrHandler = getSessionAttributesHandler(handlerMethod);
//获取handlerType 
		Class<&#63;> handlerType = handlerMethod.getBeanType();
//获取添加了@ModelAttribute注解的方法		
		Set<Method> methods = this.modelAttributeCache.get(handlerType);
		if (methods == null) {
			methods = MethodIntrospector.selectMethods(handlerType, MODEL_ATTRIBUTE_METHODS);
			this.modelAttributeCache.put(handlerType, methods);
		}
		List<InvocableHandlerMethod> attrMethods = new ArrayList<>();
//从controllerAdviceBean中获取适合当前handlerType的method，
//并封装为一个个InvocableHandlerMethod然后添加到attrMethods
		// Global methods first
		this.modelAttributeAdviceCache.forEach((controllerAdviceBean, methodSet) -> {
			if (controllerAdviceBean.isApplicableToBeanType(handlerType)) {
				Object bean = controllerAdviceBean.resolveBean();
				for (Method method : methodSet) {
					attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
				}
			}
		});
//遍历methods并封装为一个个InvocableHandlerMethod然后添加到attrMethods
		for (Method method : methods) {
			Object bean = handlerMethod.getBean();
			attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
		}
//根据attrMethods, binderFactory, sessionAttrHandler创建一个ModelFactory对象
		return new ModelFactory(attrMethods, binderFactory, sessionAttrHandler);
	}

public SessionAttributesHandler(Class<&#63;> handlerType, SessionAttributeStore sessionAttributeStore) {
		Assert.notNull(sessionAttributeStore, "SessionAttributeStore may not be null");
		this.sessionAttributeStore = sessionAttributeStore;
//尝试从handlerType获取@SessionAttributes注解
		SessionAttributes ann = AnnotatedElementUtils.findMergedAnnotation(handlerType, SessionAttributes.class);
		if (ann != null) {
		//注解的name属性值放入attributeNames中
			Collections.addAll(this.attributeNames, ann.names());
		//注解的type属性值放入	attributeTypes
			Collections.addAll(this.attributeTypes, ann.types());
		}
		//把所有的attributeNames放入knownAttributeNames
		//在初始化model方法initModel将会使用这些数据
		this.knownAttributeNames.addAll(this.attributeNames);
	}

ServletInvocableHandlerMethod invocableMethod = this.createInvocableHandlerMethod(handlerMethod);
if (this.argumentResolvers != null) {
   invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
 }

 if (this.returnValueHandlers != null) {
   invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
 }

 invocableMethod.setDataBinderFactory(binderFactory);
 invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);

protected HandlerMethod(HandlerMethod handlerMethod) {
		Assert.notNull(handlerMethod, "HandlerMethod is required");
		this.bean = handlerMethod.bean;
		this.beanFactory = handlerMethod.beanFactory;
		this.beanType = handlerMethod.beanType;
		this.method = handlerMethod.method;
		this.bridgedMethod = handlerMethod.bridgedMethod;
		this.parameters = handlerMethod.parameters;
		this.responseStatus = handlerMethod.responseStatus;
		this.responseStatusReason = handlerMethod.responseStatusReason;
		this.description = handlerMethod.description;
		this.resolvedFromHandlerMethod = handlerMethod.resolvedFromHandlerMethod;
	}

//创建ModelAndViewContainer 实例对象
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
//从请求中获取InputFlashMap并把其数据放入defaultModel中，flashmap的作用是在redirect中传递参数
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
//调用modelFactory对model进行初始化
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
//重定向时忽略默认Model
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

public void initModel(NativeWebRequest request, ModelAndViewContainer container, HandlerMethod handlerMethod)
			throws Exception {
	//获取会话属性键值对
		Map<String, &#63;> sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
		
		//对model中属性-值进行合并处理：称之为补缺更合适
		//如果model中不存在，则放入---这个很重要
		container.mergeAttributes(sessionAttributes);
		
		//调用标注了@ModelAttribute注解的方法
		invokeModelAttributeMethods(request, container);

		//如果handlerMethod的方法参数标注了@ModelAttribute注解并且在sessionAttributetes存在/或类型匹配，则对其进行遍历
		//尝试获取值，如果获取不到值就会抛出异常；如果获取到值就会放到model-defaultModel中
		for (String name : findSessionAttributeArguments(handlerMethod)) {
			if (!container.containsAttribute(name)) {
				Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
				if (value == null) {
					throw new HttpSessionRequiredException("Expected session attribute '" + name + "'", name);
				}
				container.addAttribute(name, value);
			}
		}
	}

public Map<String, Object> retrieveAttributes(WebRequest request) {
		Map<String, Object> attributes = new HashMap<>();
		//遍历通过@SessionAttributes注解获取的name
		for (String name : this.knownAttributeNames) {
		//从session中获取name对应的值
			Object value = this.sessionAttributeStore.retrieveAttribute(request, name);
			if (value != null) {
			//如果值存在，则放入attributes
				attributes.put(name, value);
			}
		}
		return attributes;
	}

#也就是说遍历sessionAttributes ，如果model中不存在，就放入。如果存在，就跳过！注意，不会进行值覆盖
 public ModelMap mergeAttributes(@Nullable Map<String, &#63;> attributes) {
    if (attributes != null) {
      attributes.forEach((key, value) -> {
        if (!this.containsKey(key)) {
          this.put(key, value);//this这里值的是modelMap，也就是defaultModel
        }
      });
    }
    return this;
  }

private void invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer container)
			throws Exception {
//循环调用modelMethod 
		while (!this.modelMethods.isEmpty()) {
			InvocableHandlerMethod modelMethod = getNextModelMethod(container).getHandlerMethod();
			ModelAttribute ann = modelMethod.getMethodAnnotation(ModelAttribute.class);
			Assert.state(ann != null, "No ModelAttribute annotation");
			if (container.containsAttribute(ann.name())) {
				if (!ann.binding()) {
					container.setBindingDisabled(ann.name());
				}
				continue;
			}
			//反射调用方法并获取返回值
			Object returnValue = modelMethod.invokeForRequest(request, container);
			//如果返回值不为空，就放入model-(returnValueName, returnValue)
			if (!modelMethod.isVoid()){
				String returnValueName = getNameForReturnValue(returnValue, modelMethod.getReturnType());
				if (!ann.binding()) {
					container.setBindingDisabled(returnValueName);
				}
				if (!container.containsAttribute(returnValueName)) {
					container.addAttribute(returnValueName, returnValue);
				}
			}
		}
	}

//从方法参数中找到在(@SessionAttributes注解的属性/参数)中存在的或者类型匹配
	 // 且方法参数上标注了@ModelAttribute注解的属性名集合
	private List<String> findSessionAttributeArguments(HandlerMethod handlerMethod) {
		List<String> result = new ArrayList<>();
		for (MethodParameter parameter : handlerMethod.getMethodParameters()) {
			if (parameter.hasParameterAnnotation(ModelAttribute.class)) {
				String name = getNameForParameter(parameter);
				Class<&#63;> paramType = parameter.getParameterType();
				if (this.sessionAttributesHandler.isHandlerSessionAttribute(name, paramType)) {
					result.add(name);
				}
			}
		}
		return result;
	}

AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout);

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();
	LogFormatUtils.traceDebug(logger, traceOn -> {
		String formatted = LogFormatUtils.formatValue(result, !traceOn);
		return "Resume with async result [" + formatted + "]";
	});
	invocableMethod = invocableMethod.wrapConcurrentResult(result);
}

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
//调用目标方法并获取返回值，这里对应 【3.1】 InvocableHandlerMethod.invokeForRequest调用目标方法
		Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);

//设置响应状态
		setResponseStatus(webRequest);

//如果返回值为null，则将mavContainer.RequestHandled设置为true，表示已经处理不需要视图解析
		if (returnValue == null) {
			if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
				disableContentCachingIfNecessary(webRequest);
				mavContainer.setRequestHandled(true);
				return;
			}
		}
		else if (StringUtils.hasText(getResponseStatusReason())) {
			mavContainer.setRequestHandled(true);
			return;
		}
//将mavContainer.RequestHandled设置为false
		mavContainer.setRequestHandled(false);
		Assert.state(this.returnValueHandlers != null, "No return value handlers");

//返回值进行处理 ，这里对应【3.2】
		try {
			this.returnValueHandlers.handleReturnValue(
					returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
		}
		catch (Exception ex) {
			if (logger.isTraceEnabled()) {
				logger.trace(formatErrorForReturnValue(returnValue), ex);
			}
			throw ex;
		}
	}

public void setRequestHandled(boolean requestHandled) {
		this.requestHandled = requestHandled;
	}

public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
		Object... providedArgs) throws Exception {
//解析参数--这里对应 1
	Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
	if (logger.isTraceEnabled()) {
		logger.trace("Arguments: " + Arrays.toString(args));
	}
	//根据上面得到的参数值调用目标方法 这里对应 2 
	return doInvoke(args);
}

protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
//获取到方法的参数对象  MethodParameter[]数组
		MethodParameter[] parameters = getMethodParameters();

//如果为空，返回空参数组
		if (ObjectUtils.isEmpty(parameters)) {
			return EMPTY_ARGS;
		}
		Object[] args = new Object[parameters.length];
		
		//遍历MethodParameter[] parameters，对每一个方法参数对象获取到具体参数并解析得到参数值
		for (int i = 0; i < parameters.length; i++) {
			MethodParameter parameter = parameters[i];
			//绑定参数名称发现器
			parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
			
			//从providedArgs中尝试获取到参数名
			args[i] = findProvidedArgument(parameter, providedArgs);
			if (args[i] != null) {
				continue;
			}
			//如果方法参数解析器不支持parameter，则抛出异常
			if (!this.resolvers.supportsParameter(parameter)) {
				throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
			}
			try {
			//使用参数解析器解析参数获取到值，下面会重点分析
				args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
			}
			catch (Exception ex) {
				// Leave stack trace for later, exception may actually be resolved and handled...
				if (logger.isDebugEnabled()) {
					String exMsg = ex.getMessage();
					if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {
						logger.debug(formatArgumentError(parameter, exMsg));
					}
				}
				throw ex;
			}
		}
		return args;
	}

private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache =
			new ConcurrentHashMap<>(256);

private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
//如果缓存中有，则直接返回
		HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
		//如果缓存中没有就尝试从解析器列表中获取一个支持parameter的，并将解析器 parameter放入缓存
		if (result == null) {
			for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
				if (resolver.supportsParameter(parameter)) {
					result = resolver;
					this.argumentResolverCache.put(parameter, result);
					break;
				}
			}
		}
		return result;
	}

args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);

public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
		//这里获取具体的、实际的参数解析器！
		HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
		if (resolver == null) {
			throw new IllegalArgumentException("Unsupported parameter type [" +
					parameter.getParameterType().getName() + "]. supportsParameter should be called first.");
		}
		return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
	}

public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
		//这里获取具体的、实际的参数解析器！
		HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
		if (resolver == null) {
			throw new IllegalArgumentException("Unsupported parameter type [" +
					parameter.getParameterType().getName() + "]. supportsParameter should be called first.");
		}
		return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
	}

public static String getVariableNameForParameter(MethodParameter parameter) {
		Assert.notNull(parameter, "MethodParameter must not be null");
		Class<&#63;> valueClass;
		boolean pluralize = false;
		String reactiveSuffix = "";
//判断参数类型是不是数组
		if (parameter.getParameterType().isArray()) {
			valueClass = parameter.getParameterType().getComponentType();
			pluralize = true;
		}
		// 判断是不是集合类型
		else if (Collection.class.isAssignableFrom(parameter.getParameterType())) {
			valueClass = ResolvableType.forMethodParameter(parameter).asCollection().resolveGeneric();
			if (valueClass == null) {
				throw new IllegalArgumentException(
						"Cannot generate variable name for non-typed Collection parameter type");
			}
			pluralize = true;
		}
		else {
		//获取参数类型，这里是com.alibaba.fastjson.JSONObject
			valueClass = parameter.getParameterType();
			ReactiveAdapter adapter = ReactiveAdapterRegistry.getSharedInstance().getAdapter(valueClass);
			if (adapter != null && !adapter.getDescriptor().isNoValue()) {
				reactiveSuffix = ClassUtils.getShortName(valueClass);
				valueClass = parameter.nested().getNestedParameterType();
			}
		}
		String name = ClassUtils.getShortNameAsProperty(valueClass);
		return (pluralize &#63; pluralize(name) : name + reactiveSuffix);
	}

if (binderFactory != null) {
			WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
			if (arg != null) {
				validateIfApplicable(binder, parameter);
				if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
					throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
				}
			}
			if (mavContainer != null) {
				mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
			}
		}

public final WebDataBinder createBinder(
			NativeWebRequest webRequest, @Nullable Object target, String objectName) throws Exception {
//创建WebDataBinder 实例
		WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest);
		//如果初始化器不为null，进行初始化
		if (this.initializer != null) {
			this.initializer.initBinder(dataBinder, webRequest);
		}
		//这是扩展接口，可以用户自定义以进行更深入的初始化
		initBinder(dataBinder, webRequest);
		return dataBinder;
	}

public DataBinder(@Nullable Object target, String objectName) {
    this.ignoreUnknownFields = true;
    this.ignoreInvalidFields = false;
    this.autoGrowNestedPaths = true;
    this.autoGrowCollectionLimit = 256;
    this.bindingErrorProcessor = new DefaultBindingErrorProcessor();
    this.validators = new ArrayList();
    this.target = ObjectUtils.unwrapOptional(target);
    this.objectName = objectName;
  }

public void initBinder(WebDataBinder binder) {
		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);
		}
		//如果target不为null且校验器不为空，就绑定校验器
		if (this.validator != null && binder.getTarget() != null &&
				this.validator.supports(binder.getTarget().getClass())) {
			binder.setValidator(this.validator);
		}
		//绑定类型转换服务类
		if (this.conversionService != null) {
			binder.setConversionService(this.conversionService);
		}
		if (this.propertyEditorRegistrars != null) {
			for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) {
				propertyEditorRegistrar.registerCustomEditors(binder);
			}
		}
	}

public void initBinder(WebDataBinder binder) {
		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);
		}
		//如果target不为null且校验器不为空，就绑定校验器
		if (this.validator != null && binder.getTarget() != null &&
				this.validator.supports(binder.getTarget().getClass())) {
			binder.setValidator(this.validator);
		}
		//绑定类型转换服务类
		if (this.conversionService != null) {
			binder.setConversionService(this.conversionService);
		}
		if (this.propertyEditorRegistrars != null) {
			for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) {
				propertyEditorRegistrar.registerCustomEditors(binder);
			}
		}
	}

protected Object doInvoke(Object... args) throws Exception {
//获取桥接方法并使方法可以调用
		ReflectionUtils.makeAccessible(getBridgedMethod());
		try {
//		获取桥接方法以及对应的bean 参数值，然后反射调用
			return getBridgedMethod().invoke(getBean(), args);
		}
		catch (IllegalArgumentException ex) {
			assertTargetBean(getBridgedMethod(), getBean(), args);
			String text = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument");
			throw new IllegalStateException(formatInvokeError(text, args), ex);
		}
		catch (InvocationTargetException ex) {
			// Unwrap for HandlerExceptionResolvers ...
			Throwable targetException = ex.getTargetException();
			if (targetException instanceof RuntimeException) {
				throw (RuntimeException) targetException;
			}
			else if (targetException instanceof Error) {
				throw (Error) targetException;
			}
			else if (targetException instanceof Exception) {
				throw (Exception) targetException;
			}
			else {
				throw new IllegalStateException(formatInvokeError("Invocation failure", args), targetException);
			}
		}
	}

this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);

public MethodParameter getReturnValueType(@Nullable Object returnValue) {
		return new ReturnValueMethodParameter(returnValue);
	}

private class ReturnValueMethodParameter extends HandlerMethodParameter {

		@Nullable
		private final Object returnValue;

		public ReturnValueMethodParameter(@Nullable Object returnValue) {
			super(-1);
			this.returnValue = returnValue;
		}

		protected ReturnValueMethodParameter(ReturnValueMethodParameter original) {
			super(original);
			this.returnValue = original.returnValue;
		}

		@Override
		public Class<&#63;> getParameterType() {
			return (this.returnValue != null &#63; this.returnValue.getClass() : super.getParameterType());
		}

		@Override
		public ReturnValueMethodParameter clone() {
			return new ReturnValueMethodParameter(this);
		}
	}

private class ReturnValueMethodParameter extends HandlerMethodParameter {

		@Nullable
		private final Object returnValue;

		public ReturnValueMethodParameter(@Nullable Object returnValue) {
			super(-1);
			this.returnValue = returnValue;
		}

		protected ReturnValueMethodParameter(ReturnValueMethodParameter original) {
			super(original);
			this.returnValue = original.returnValue;
		}

		@Override
		public Class<&#63;> getParameterType() {
			return (this.returnValue != null &#63; this.returnValue.getClass() : super.getParameterType());
		}

		@Override
		public ReturnValueMethodParameter clone() {
			return new ReturnValueMethodParameter(this);
		}
	}

@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
	ModelAndViewContainer mavContainer, NativeWebRequest webRequest)
	throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
//设置请求已经被处理
mavContainer.setRequestHandled(true);

//获取一个ServletServerHttpRequest实例-构造函数参数为HttpServletRequest
ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
//获取一个 实例ServletServerHttpResponse ，构造函数参数为HttpServletResponse
ServletServerHttpResponse outputMessage = createOutputMessage(webRequest);

// Try even with null return value. ResponseBodyAdvice could get involved.
writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
}

protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
			ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
			throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {

		Object body;
		Class<&#63;> valueType;
		Type targetType;

		if (value instanceof CharSequence) {
			body = value.toString();
			valueType = String.class;
			targetType = String.class;
		}
		else {
			body = value;
//值类型，这里是class com.baby.healthcare.common.ResponseBean
			valueType = getReturnValueType(body, returnType);
			targetType = GenericTypeResolver.resolveType(getGenericType(returnType), returnType.getContainingClass());
		}
//判断是否Resource 或InputStreamSource
		if (isResourceType(value, returnType)) {
			outputMessage.getHeaders().set(HttpHeaders.ACCEPT_RANGES, "bytes");
			if (value != null && inputMessage.getHeaders().getFirst(HttpHeaders.RANGE) != null &&
					outputMessage.getServletResponse().getStatus() == 200) {
				Resource resource = (Resource) value;
				try {
					List<HttpRange> httpRanges = inputMessage.getHeaders().getRange();
					outputMessage.getServletResponse().setStatus(HttpStatus.PARTIAL_CONTENT.value());
					body = HttpRange.toResourceRegions(httpRanges, resource);
					valueType = body.getClass();
					targetType = RESOURCE_REGION_LIST_TYPE;
				}
				catch (IllegalArgumentException ex) {
					outputMessage.getHeaders().set(HttpHeaders.CONTENT_RANGE, "bytes */" + resource.contentLength());
					outputMessage.getServletResponse().setStatus(HttpStatus.REQUESTED_RANGE_NOT_SATISFIABLE.value());
				}
			}
		}

		MediaType selectedMediaType = null;
//响应内容类型
		MediaType contentType = outputMessage.getHeaders().getContentType();
		boolean isContentTypePreset = contentType != null && contentType.isConcrete();
		if (isContentTypePreset) {
			if (logger.isDebugEnabled()) {
				logger.debug("Found 'Content-Type:" + contentType + "' in response");
			}
			selectedMediaType = contentType;
		}
		else {
			HttpServletRequest request = inputMessage.getServletRequest();
			//获取接收的MediaType
			List<MediaType> acceptableTypes = getAcceptableMediaTypes(request);
			//获取返回结果的MediaType
			List<MediaType> producibleTypes = getProducibleMediaTypes(request, valueType, targetType);
//如果body不为空，但是没有合适的返回结果类型，则抛出异常
			if (body != null && producibleTypes.isEmpty()) {
				throw new HttpMessageNotWritableException(
						"No converter found for return value of type: " + valueType);
			}
//循环比较，从acceptableTypes找到适配producibleTypes的
			List<MediaType> mediaTypesToUse = new ArrayList<>();
			for (MediaType requestedType : acceptableTypes) {
				for (MediaType producibleType : producibleTypes) {
					if (requestedType.isCompatibleWith(producibleType)) {
						mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType));
					}
				}
			}
			if (mediaTypesToUse.isEmpty()) {
				if (body != null) {
					throw new HttpMediaTypeNotAcceptableException(producibleTypes);
				}
				if (logger.isDebugEnabled()) {
					logger.debug("No match for " + acceptableTypes + ", supported: " + producibleTypes);
				}
				return;
			}
//对MediaType进行排序
			MediaType.sortBySpecificityAndQuality(mediaTypesToUse);

			for (MediaType mediaType : mediaTypesToUse) {
				if (mediaType.isConcrete()) {
					selectedMediaType = mediaType;
					break;
				}
				else if (mediaType.isPresentIn(ALL_APPLICATION_MEDIA_TYPES)) {
					selectedMediaType = MediaType.APPLICATION_OCTET_STREAM;
					break;
				}
			}

			if (logger.isDebugEnabled()) {
				logger.debug("Using '" + selectedMediaType + "', given " +
						acceptableTypes + " and supported " + producibleTypes);
			}
		}

		if (selectedMediaType != null) {
			selectedMediaType = selectedMediaType.removeQualityValue();
			for (HttpMessageConverter<&#63;> converter : this.messageConverters) {
				GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter &#63;
						(GenericHttpMessageConverter<&#63;>) converter : null);
				if (genericConverter != null &#63;
						((GenericHttpMessageConverter) converter).canWrite(targetType, valueType, selectedMediaType) :
						converter.canWrite(valueType, selectedMediaType)) {
					body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType,
							(Class<&#63; extends HttpMessageConverter<&#63;>>) converter.getClass(),
							inputMessage, outputMessage);
					if (body != null) {
						Object theBody = body;
						LogFormatUtils.traceDebug(logger, traceOn ->
								"Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]");
						addContentDispositionHeader(inputMessage, outputMessage);
						if (genericConverter != null) {
							genericConverter.write(body, targetType, selectedMediaType, outputMessage);
						}
						else {
							((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage);
						}
					}
					else {
						if (logger.isDebugEnabled()) {
							logger.debug("Nothing to write: null body");
						}
					}
					return;
				}
			}
		}

		if (body != null) {
			Set<MediaType> producibleMediaTypes =
					(Set<MediaType>) inputMessage.getServletRequest()
							.getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);

			if (isContentTypePreset || !CollectionUtils.isEmpty(producibleMediaTypes)) {
				throw new HttpMessageNotWritableException(
						"No converter for [" + valueType + "] with preset Content-Type '" + contentType + "'");
			}
			throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes);
		}
	}

//循环比较，从acceptableTypes找到适配producibleTypes的
			List<MediaType> mediaTypesToUse = new ArrayList<>();
			for (MediaType requestedType : acceptableTypes) {
				for (MediaType producibleType : producibleTypes) {
					if (requestedType.isCompatibleWith(producibleType)) {
						mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType));
					}
				}
			}

for (HttpMessageConverter<&#63;> converter : this.messageConverters) {
GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter &#63;
			(GenericHttpMessageConverter<&#63;>) converter : null);
	if (genericConverter != null &#63;
			((GenericHttpMessageConverter) converter).canWrite(targetType, valueType, selectedMediaType) :
			converter.canWrite(valueType, selectedMediaType)) {
		body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType,
				(Class<&#63; extends HttpMessageConverter<&#63;>>) converter.getClass(),
				inputMessage, outputMessage);
		if (body != null) {
			Object theBody = body;
			LogFormatUtils.traceDebug(logger, traceOn ->
					"Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]");
			addContentDispositionHeader(inputMessage, outputMessage);
			if (genericConverter != null) {
				genericConverter.write(body, targetType, selectedMediaType, outputMessage);
			}
			else {
				((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage);
			}
		}
		else {
			if (logger.isDebugEnabled()) {
				logger.debug("Nothing to write: null body");
			}
		}
		return;
	}
}

@Nullable
private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
		ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception {
//更新model
	modelFactory.updateModel(webRequest, mavContainer);
	//如果请求已经处理完，则直接返回，不会再尝试创建mav 
	if (mavContainer.isRequestHandled()) {
		return null;
	}
	ModelMap model = mavContainer.getModel();
	ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
	if (!mavContainer.isViewReference()) {
		mav.setView((View) mavContainer.getView());
	}
	if (model instanceof RedirectAttributes) {
		Map<String, &#63;> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();
		HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
		if (request != null) {
			RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
		}
	}
	return mav;
}

#标记这个请求已经被完成
##调用所有的销毁回调方法
##更新请求过程中访问到的会话属性
public void requestCompleted() {
		executeRequestDestructionCallbacks();
		updateAccessedSessionAttributes();
		this.requestActive = false;
	}

private void executeRequestDestructionCallbacks() {
//这里使用synchronized 保证每个runnable 只被调用一次
	synchronized (this.requestDestructionCallbacks) {
		for (Runnable runnable : this.requestDestructionCallbacks.values()) {
			runnable.run();
		}
		this.requestDestructionCallbacks.clear();
	}
}

if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
	if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
			applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
		}
		else {
			prepareResponse(response);
		}
}

private void applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv) throws Exception {
		if (mv != null && !mv.hasView()) {
			String defaultViewName = getDefaultViewName(request);
			if (defaultViewName != null) {
				mv.setViewName(defaultViewName);
			}
		}
	}

void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
			throws Exception {

		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				interceptor.postHandle(request, response, this.handler, mv);
			}
		}
	}

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
			@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
			@Nullable Exception exception) throws Exception {

		boolean errorView = false;

		if (exception != null) {
			if (exception instanceof ModelAndViewDefiningException) {
				logger.debug("ModelAndViewDefiningException encountered", exception);
				mv = ((ModelAndViewDefiningException) exception).getModelAndView();
			}
			else {
				Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
				mv = processHandlerException(request, response, handler, exception);
				errorView = (mv != null);
			}
		}

		// Did the handler return a view to render?
		if (mv != null && !mv.wasCleared()) {
			render(mv, request, response);
			if (errorView) {
				WebUtils.clearErrorRequestAttributes(request);
			}
		}
		else {
			if (logger.isTraceEnabled()) {
				logger.trace("No view rendering, null ModelAndView returned.");
			}
		}

		if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
			// Concurrent handling started during a forward
			return;
		}

		if (mappedHandler != null) {
			// Exception (if any) is already handled..
			mappedHandler.triggerAfterCompletion(request, response, null);
		}
	}

void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
		throws Exception {

	HandlerInterceptor[] interceptors = getInterceptors();
	if (!ObjectUtils.isEmpty(interceptors)) {
		for (int i = this.interceptorIndex; i >= 0; i--) {
			HandlerInterceptor interceptor = interceptors[i];
			try {
				interceptor.afterCompletion(request, response, this.handler, ex);
			}
			catch (Throwable ex2) {
				logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
			}
		}
	}
}

if (asyncManager.isConcurrentHandlingStarted()) {
	// Instead of postHandle and afterCompletion
	if (mappedHandler != null) {
		mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
	}
}else {
	// Clean up any resources used by a multipart request.
	if (multipartRequestParsed) {
		cleanupMultipart(processedRequest);
	}
}