springmvc--4--HandlerAdapter处理器适配器

朴灿烈づ我的快乐病毒、 2022-10-29 06:27 152阅读 0赞

# springmvc–`HandlerAdapter`处理器适配器 #

### 文章目录 ###

* springmvc--\`HandlerAdapter\`处理器适配器
 * 1 用途
 * 2 \`springmvc\`默认的\`HandlerAdapter\`
 * 3 \`HandlerAdapter\`接口
 * 4 \`RequestMappingHandlerAdapter\`的构造方法
 * 5 \`afterPropertiesSet()\`方法（\`InitializingBean\`接口唯一方法）
 * * 5.1 找出所有标注\`@ControllerAdvice\`注解的\`bean\`，并进行初步处理
 * 5.2 \`springmvc\`三种解析器(参数，绑定器，返回值）的默认配置
 * 6 \`supports(Object handler)\`方法，判断处理器适配器是否支持该处理器方法
 * 7 \`getLastModified(HttpServletRequest request, Object handler)\`方法，获取上一次修改请求的时间
 * 8 \`handle(HttpServletRequest request, HttpServletResponse response, Object handler)\`方法， 完成处理器方法的调用
 * * 8.1 \`checkRequest(HttpServletRequest request) \`方法，检查请求
 * 8.2 \`invokeHandlerMethod()\`方法，执行处理器方法并返回一个\`ModelAndView\`对象
 * * 8.2.1 \`getDataBinderFactory(handlerMethod)\`方法， 获取数据绑定器工厂
 * * 8.2.1.1 创建并初始化一个绑定器方法\`InvocableHandlerMethod\`
 * 8.2.1.2 创建数据绑定器工厂\`ServletRequestDataBinderFactory\`
 * 8.2.2 \`getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory)\`方法，获取模型工厂
 * * 8.2.2.1 获取\`session属性处理器\`
 * 8.2.2.2 创建并初始化一个模型属性方法\`InvocableHandlerMethod\`
 * 8.2.3 创建\`ServletInvocableHandlerMethod\`
 * 8.2.4 获取\`ModelAndView\`对象
 * 9 \`ControllerAdviceBean\`类，封装\`@ControllerAdvice\`注解的\`bean\`
 * * 9.1 构造方法
 * 9.2 获取容器中有\`@ControllerAdvice\`注解的\`bean\`，并封装为\`ControllerAdviceBean\`
 * 9.3 判断\`@ControllerAdvice\`中的方法是否对该处理器方法所在类生效
 * 9.4 获取\`ControllerAdviceBean\`对应的\`bean\`对象
 * 10 \`HandlerTypePredicate\`，断言器，用来匹配请求处理组件的类型
 * * 10.1 嵌套类\`Builder\`（建造者模式）
 * 10.2 \`test()\`方法（\`Predicate\`断言接口的唯一方法）
 * 11 \`ServletWebRequest\`类，适配\`HttpServletRequest\`
 * * 11.1 \`requestCompleted()\`方法，设置请求已完成
 * 12 \`WebDataBinderFactory\`数据绑定器工厂
 * * 12.1 \`ServletRequestDataBinderFactory\`的构造方法
 * 12.2 \`createBinder(NativeWebRequest webRequest, @Nullable Object target, String objectName)\`方法，创建属性对应的数据绑定器
 * 13 \`SessionAttributesHandler\` 会话属性处理器
 * * 13.1 \`SessionAttributeStore\`策略接口，定义操作\`session域属性\`的规范
 * 13.2 \`SessionAttributesHandler\`的构造方法
 * 13.3 \`retrieveAttributes(WebRequest request)\`方法，得到\`session\`中的已知属性的值
 * 13.4 \`isHandlerSessionAttribute(String attributeName, Class<?> attributeType)\`方法，判断属性名称或属性类型是否与用户通过\`@SessionAttributes\`注解指定的属性匹配
 * 13.5 \`cleanupAttributes(WebRequest request)\`方法，清理会话属性
 * 13.6 \`storeAttributes(WebRequest request, Map

# 1 用途 #

> 帮助`DispatcherServlet`调用处理器方法。
> 
> `DispatcherServlet`不管实际如何调用该处理器方法，它只需要调用`handlerAdapter.handle(processedRequest, response, mappedHandler.getHandler())`方法，即完成了处理器方法调用。具体的调用逻辑由`HandlerAdapter`实现类完成。

# 2 `springmvc`默认的`HandlerAdapter` #

`springmvc`会自动的注册`4`种类型的`HandlerAdapter`，它们之间的关系如下面类图所示

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMDEyOTgx_size_16_color_FFFFFF_t_70_pic_center]

> 注意：`HandlerMapping`与`HandlerAdapter`是一一对应的，而上篇文章说的是`RequestMappingHandlerMapping`，所以这里只看`RequestMappingHandlerAdapter`（支持`@RequestMapping`注解）。况且另外`3`种方式基本上被淘汰了。

# 3 `HandlerAdapter`接口 #

public interface HandlerAdapter { 
    
        /** * 该处理器适配器是否支持该处理器方法 */
        boolean supports(Object handler);
    
        /** * 完成该处理器方法的调用 */
        @Nullable
        ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
    
        /** * Same contract as for HttpServlet's {@code getLastModified} method. * Can simply return -1 if there's no support in the handler class. * @param request current HTTP request * @param handler the handler to use * @return the lastModified value for the given handler * @see javax.servlet.http.HttpServlet#getLastModified * @see org.springframework.web.servlet.mvc.LastModified#getLastModified */
        long getLastModified(HttpServletRequest request, Object handler);
    
    }

> 该接口中有`3`个方法，下面我们就来看一下这`3`个方法的具体原理

# 4 `RequestMappingHandlerAdapter`的构造方法 #

//消息转换器
 private List<HttpMessageConverter<?>> messageConverters;
 
 public RequestMappingHandlerAdapter() { 
 this.messageConverters = new ArrayList<>(4);
 this.messageConverters.add(new ByteArrayHttpMessageConverter());
 this.messageConverters.add(new StringHttpMessageConverter());
 try { 
 this.messageConverters.add(new SourceHttpMessageConverter<>());
 }
 catch (Error err) { 
 // Ignore when no TransformerFactory implementation is available
 }
 this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
 }

> 构造方法只是向里面放入几个`HttpMessageConverter`
> 
>  *  `ByteArrayHttpMessageConverter`
>  *  `StringHttpMessageConverter`
>  *  `SourceHttpMessageConverter`
>  *  `AllEncompassingFormHttpMessageConverter`

# 5 `afterPropertiesSet()`方法（`InitializingBean`接口唯一方法） #

> 该方法在`bean`初始化阶段被调用

/** * 这3个属性类型是典型的组合模式。 * XXXResolverComposite持有多个解析器，内部通过遍历这些解析器，使用第一个可以完成解析的解析器 * 进行解析 */
 @Nullable
 private HandlerMethodArgumentResolverComposite argumentResolvers;
 @Nullable
 private HandlerMethodArgumentResolverComposite initBinderArgumentResolvers;
 @Nullable
 private HandlerMethodReturnValueHandlerComposite returnValueHandlers;
 
 
 @Override
 public void afterPropertiesSet() { 
 // Do this first, it may add ResponseBody advice beans
 //找出所有标注@ControllerAdvice注解的bean，并进行初步处理,见5.1
 initControllerAdviceCache();
 
 //用户未进行手动配置，就会使用springmvc默认配置的解析器，见5.2
 if (this.argumentResolvers == null) { 
 List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
 this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
 }
 if (this.initBinderArgumentResolvers == null) { 
 List<HandlerMethodArgumentResolver> resolvers = getDefaultInitBinderArgumentResolvers();
 this.initBinderArgumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
 }
 if (this.returnValueHandlers == null) { 
 List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers();
 this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
 }
 }

## 5.1 找出所有标注`@ControllerAdvice`注解的`bean`，并进行初步处理 ##

//过滤器，有@ModelAttribute注解没有@RequestMapping注解的方法
 public static final MethodFilter MODEL_ATTRIBUTE_METHODS = method ->
 (!AnnotatedElementUtils.hasAnnotation(method, RequestMapping.class) &&
 AnnotatedElementUtils.hasAnnotation(method, ModelAttribute.class));
 //过滤器，有@InitBinder注解的方法
 public static final MethodFilter INIT_BINDER_METHODS = method ->
 AnnotatedElementUtils.hasAnnotation(method, InitBinder.class);
 
 //保存RequestBodyAdvice对象和ResponseBodyAdvice
 private final List<Object> requestResponseBodyAdvice = new ArrayList<>();
 
 
 private void initControllerAdviceCache() { 
 if (getApplicationContext() == null) { 
 return;
 }
 
 //获取容器中有@ControllerAdvice注解的bean，并封装为ControllerAdviceBean,见9
 List<ControllerAdviceBean> adviceBeans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
 
 List<Object> requestResponseBodyAdviceBeans = new ArrayList<>();
 
 //下面开始对@ControllerAdvice注解的bean进行处理
 for (ControllerAdviceBean adviceBean : adviceBeans) { 
 Class<?> beanType = adviceBean.getBeanType();
 if (beanType == null) { 
 throw new IllegalStateException("Unresolvable type for ControllerAdviceBean: " + adviceBean);
 }
 /** * 会对@ControllerAdvice注解标注的bean过滤 * 得到有@ModelAttribute注解没有@RequestMapping注解的方法 */
 Set<Method> attrMethods = MethodIntrospector.selectMethods(beanType, MODEL_ATTRIBUTE_METHODS);
 //缓存
 if (!attrMethods.isEmpty()) { 
 this.modelAttributeAdviceCache.put(adviceBean, attrMethods);
 }
 /** * 会对@ControllerAdvice注解标注的bean过滤 * 得到有@InitBinder注解的方法 */
 Set<Method> binderMethods = MethodIntrospector.selectMethods(beanType, INIT_BINDER_METHODS);
 //缓存
 if (!binderMethods.isEmpty()) { 
 this.initBinderAdviceCache.put(adviceBean, binderMethods);
 }
 /** * RequestBodyAdvice允许用户在读取和类型转换之前自定义请求体 * ResponseBodyAdvice允许用户@ResponseBody方法之后，HttpMessageConverter写入正文之前 * 自定义响应体 */
 if (RequestBodyAdvice.class.isAssignableFrom(beanType) || ResponseBodyAdvice.class.isAssignableFrom(beanType)) { 
 requestResponseBodyAdviceBeans.add(adviceBean);
 }
 }
 
 /** * 使用<mvc:annotation-driven>，会自动向requestResponseBodyAdvice属性中填充两个值 * JsonViewRequestBodyAdvice和JsonViewResponseBodyAdvice */
 if (!requestResponseBodyAdviceBeans.isEmpty()) { 
 this.requestResponseBodyAdvice.addAll(0, requestResponseBodyAdviceBeans);
 }
 
 if (logger.isDebugEnabled()) { 
 int modelSize = this.modelAttributeAdviceCache.size();
 int binderSize = this.initBinderAdviceCache.size();
 int reqCount = getBodyAdviceCount(RequestBodyAdvice.class);
 int resCount = getBodyAdviceCount(ResponseBodyAdvice.class);
 if (modelSize == 0 && binderSize == 0 && reqCount == 0 && resCount == 0) { 
 logger.debug("ControllerAdvice beans: none");
 }
 else { 
 logger.debug("ControllerAdvice beans: " + modelSize + " @ModelAttribute, " + binderSize +
 " @InitBinder, " + reqCount + " RequestBodyAdvice, " + resCount + " ResponseBodyAdvice");
 }
 }
 }

> 总结一下该方法做的事情
> 
> * 找到容器中有`@ControllerAdvice`注解的`bean`，并封装为`ControllerAdviceBean`
> * 对这些`bean`中的方法分类
> 
> * 有`@ModelAttribute`注解没有`@RequestMapping`注解的方法，保存到`modelAttributeAdviceCache`属性中
> * 有`@InitBinder`注解的方法，保存到`initBinderAdviceCache`属性中
> * 实现了`RequestBodyAdvice`接口或`ResponseBodyAdvice`接口的方法，保存到`requestResponseBodyAdvice`属性中
> 
> 注意:`springmvc`配置文件中使用`<mvc:annotation-driven>`，会自动向`requestResponseBodyAdvice`属性中填充两个值
> 
> * `JsonViewRequestBodyAdvice`
> * `JsonViewResponseBodyAdvice`

## 5.2 `springmvc`三种解析器(参数，绑定器，返回值）的默认配置 ##

/** * Return the list of argument resolvers to use including built-in resolvers * and custom resolvers provided via {@link #setCustomArgumentResolvers}. */
 private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() { 
 List<HandlerMethodArgumentResolver> resolvers = new ArrayList<>(30);
 
 // Annotation-based argument resolution
 resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));
 resolvers.add(new RequestParamMapMethodArgumentResolver());
 resolvers.add(new PathVariableMethodArgumentResolver());
 resolvers.add(new PathVariableMapMethodArgumentResolver());
 resolvers.add(new MatrixVariableMethodArgumentResolver());
 resolvers.add(new MatrixVariableMapMethodArgumentResolver());
 resolvers.add(new ServletModelAttributeMethodProcessor(false));
 resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));
 resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters(), this.requestResponseBodyAdvice));
 resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));
 resolvers.add(new RequestHeaderMapMethodArgumentResolver());
 resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory()));
 resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));
 resolvers.add(new SessionAttributeMethodArgumentResolver());
 resolvers.add(new RequestAttributeMethodArgumentResolver());
 
 // Type-based argument resolution
 resolvers.add(new ServletRequestMethodArgumentResolver());
 resolvers.add(new ServletResponseMethodArgumentResolver());
 resolvers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));
 resolvers.add(new RedirectAttributesMethodArgumentResolver());
 resolvers.add(new ModelMethodProcessor());
 resolvers.add(new MapMethodProcessor());
 resolvers.add(new ErrorsMethodArgumentResolver());
 resolvers.add(new SessionStatusMethodArgumentResolver());
 resolvers.add(new UriComponentsBuilderMethodArgumentResolver());
 
 // Custom arguments
 if (getCustomArgumentResolvers() != null) { 
 resolvers.addAll(getCustomArgumentResolvers());
 }
 
 // Catch-all
 resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));
 resolvers.add(new ServletModelAttributeMethodProcessor(true));
 
 return resolvers;
 }
 
 
 /** * Return the list of argument resolvers to use for {@code @InitBinder} * methods including built-in and custom resolvers. */
 private List<HandlerMethodArgumentResolver> getDefaultInitBinderArgumentResolvers() { 
 List<HandlerMethodArgumentResolver> resolvers = new ArrayList<>(20);
 
 // Annotation-based argument resolution
 resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));
 resolvers.add(new RequestParamMapMethodArgumentResolver());
 resolvers.add(new PathVariableMethodArgumentResolver());
 resolvers.add(new PathVariableMapMethodArgumentResolver());
 resolvers.add(new MatrixVariableMethodArgumentResolver());
 resolvers.add(new MatrixVariableMapMethodArgumentResolver());
 resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));
 resolvers.add(new SessionAttributeMethodArgumentResolver());
 resolvers.add(new RequestAttributeMethodArgumentResolver());
 
 // Type-based argument resolution
 resolvers.add(new ServletRequestMethodArgumentResolver());
 resolvers.add(new ServletResponseMethodArgumentResolver());
 
 // Custom arguments
 if (getCustomArgumentResolvers() != null) { 
 resolvers.addAll(getCustomArgumentResolvers());
 }
 
 // Catch-all
 resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));
 
 return resolvers;
 }
 
 
 /** * Return the list of return value handlers to use including built-in and * custom handlers provided via {@link #setReturnValueHandlers}. */
 private List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers() { 
 List<HandlerMethodReturnValueHandler> handlers = new ArrayList<>(20);
 
 // Single-purpose return value types
 handlers.add(new ModelAndViewMethodReturnValueHandler());
 handlers.add(new ModelMethodProcessor());
 handlers.add(new ViewMethodReturnValueHandler());
 handlers.add(new ResponseBodyEmitterReturnValueHandler(getMessageConverters(),
 this.reactiveAdapterRegistry, this.taskExecutor, this.contentNegotiationManager));
 handlers.add(new StreamingResponseBodyReturnValueHandler());
 handlers.add(new HttpEntityMethodProcessor(getMessageConverters(),
 this.contentNegotiationManager, this.requestResponseBodyAdvice));
 handlers.add(new HttpHeadersReturnValueHandler());
 handlers.add(new CallableMethodReturnValueHandler());
 handlers.add(new DeferredResultMethodReturnValueHandler());
 handlers.add(new AsyncTaskMethodReturnValueHandler(this.beanFactory));
 
 // Annotation-based return value types
 handlers.add(new ModelAttributeMethodProcessor(false));
 handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(),
 this.contentNegotiationManager, this.requestResponseBodyAdvice));
 
 // Multi-purpose return value types
 handlers.add(new ViewNameMethodReturnValueHandler());
 handlers.add(new MapMethodProcessor());
 
 // Custom return value types
 if (getCustomReturnValueHandlers() != null) { 
 handlers.addAll(getCustomReturnValueHandlers());
 }
 
 // Catch-all
 if (!CollectionUtils.isEmpty(getModelAndViewResolvers())) { 
 handlers.add(new ModelAndViewResolverMethodReturnValueHandler(getModelAndViewResolvers()));
 }
 else { 
 handlers.add(new ModelAttributeMethodProcessor(true));
 }
 
 return handlers;
 }

> 这么多的解析器，不需要知道原理，看看名字，知道它对应的解析类型就行了。

# 6 `supports(Object handler)`方法，判断处理器适配器是否支持该处理器方法 #

> 该方法在`AbstractHandlerMethodAdapter`中实现

/** * This implementation expects the handler to be an {@link HandlerMethod}. * @param handler the handler instance to check * @return whether or not this adapter can adapt the given handler */
    @Override
    public final boolean supports(Object handler) { 
        //只要这两个条件成立，就表明支持该处理器方法
        return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
    }

`RequestMappingHandlerAdapter`中实现`supportsInternal()`方法

/** * Always return {@code true} since any method argument and return value * type will be processed in some way. A method argument not recognized * by any HandlerMethodArgumentResolver is interpreted as a request parameter * if it is a simple type, or as a model attribute otherwise. A return value * not recognized by any HandlerMethodReturnValueHandler will be interpreted * as a model attribute. */
    @Override
    protected boolean supportsInternal(HandlerMethod handlerMethod) { 
       return true;
    }

> 从上面代码我们可以发现，只要处理器方法是`HandlerMethod`类型的，就支持

# 7 `getLastModified(HttpServletRequest request, Object handler)`方法，获取上一次修改请求的时间 #

> 该方法在`AbstractHandlerMethodAdapter`中实现

/** * This implementation expects the handler to be an {@link HandlerMethod}. */
    @Override
    public final long getLastModified(HttpServletRequest request, Object handler) { 
        return getLastModifiedInternal(request, (HandlerMethod) handler);
    }

`RequestMappingHandlerAdapter`中实现`getLastModifiedInternal()`方法

/** * This implementation always returns -1. An {@code @RequestMapping} method can * calculate the lastModified value, call {@link WebRequest#checkNotModified(long)}, * and return {@code null} if the result of that call is {@code true}. */
    @Override
    protected long getLastModifiedInternal(HttpServletRequest request, HandlerMethod handlerMethod) { 
       return -1;
    }

> 总是返回`-1`，不支持这个功能

# 8 `handle(HttpServletRequest request, HttpServletResponse response, Object handler)`方法， 完成处理器方法的调用 #

> 该方法在`AbstractHandlerMethodAdapter`中实现

/** * This implementation expects the handler to be an {@link HandlerMethod}. */
    @Override
    @Nullable
    public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
        throws Exception { 
    
        return handleInternal(request, response, (HandlerMethod) handler);
    }

`RequestMappingHandlerAdapter`中实现`handleInternal()`方法，真正的方法调用逻辑

//一个响应头属性
    protected static final String HEADER_CACHE_CONTROL = "Cache-Control";
    
    //缓存的秒数，0表示不缓存
    private int cacheSecondsForSessionAttributeHandlers = 0;
    
    @Override
    protected ModelAndView handleInternal(HttpServletRequest request,
                                          HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { 
    
        ModelAndView mav;
        //检查请求，见8.1
        checkRequest(request);
    
        // Execute invokeHandlerMethod in synchronized block if required.
        /** * 会话同步 * synchronizeOnSession默认是false */
        if (this.synchronizeOnSession) { 
            HttpSession session = request.getSession(false);
            if (session != null) { 
                Object mutex = WebUtils.getSessionMutex(session);
                synchronized (mutex) { 
                    mav = invokeHandlerMethod(request, response, handlerMethod);
                }
            }
            else { 
                // No HttpSession available -> no mutex necessary
                mav = invokeHandlerMethod(request, response, handlerMethod);
            }
        }
        //非同步
        else { 
            // No synchronization on session demanded at all...
            //执行处理器方法，返回一个ModelAndView对象，见8.2
            mav = invokeHandlerMethod(request, response, handlerMethod);
        }
    
        //不包含此响应头
        if (!response.containsHeader(HEADER_CACHE_CONTROL)) { 
            //用户使用@SessionAttributes注解指定了属性
            if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) { 
                //为资源设置缓存时间
                applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
            }
            else { 
                prepareResponse(response);
            }
        }
    
        return mav;
    }

## 8.1 `checkRequest(HttpServletRequest request)`方法，检查请求 ##

//支持的请求方式，默认为null，表示支持所有
 @Nullable
 private Set<String> supportedMethods;
 //session是否必须
 private boolean requireSession = false;
 
 /** * Check the given request for supported methods and a required session, if any. * @param request current HTTP request * @throws ServletException if the request cannot be handled because a check failed * @since 4.2 */
 protected final void checkRequest(HttpServletRequest request) throws ServletException { 
 // Check whether we should support the request method.
 //当前请求方式
 String method = request.getMethod();
 /** * 如果用户设置了supportedMethods属性，表明用户只想支持它指定的方法 * 比如，如果设置POST，GET，那么将只能处理POST，GET，其他方式的请求过来，就会抛出异常 */
 if (this.supportedMethods != null && !this.supportedMethods.contains(method)) { 
 throw new HttpRequestMethodNotSupportedException(method, this.supportedMethods);
 }
 
 // Check whether a session is required.
 /** * request.getSession(false)获取当前请求对应的session， * false表示如果不存在不会创建新的session */
 if (this.requireSession && request.getSession(false) == null) { 
 throw new HttpSessionRequiredException("Pre-existing session required but none found");
 }
 }

> 检查是否支持该请求方式
> 
> 检查该请求是否必须存在`session`

## 8.2 `invokeHandlerMethod()`方法，执行处理器方法并返回一个`ModelAndView`对象 ##

//忽略重定向时的默认模型
    private boolean ignoreDefaultModelOnRedirect = false;
    
    /** * Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView} * if view resolution is required. * @since 4.2 * @see #createInvocableHandlerMethod(HandlerMethod) */
    @Nullable
    protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
                                               HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { 
    
        //创建一个请求的适配器对象，见11
        ServletWebRequest webRequest = new ServletWebRequest(request, response);
        try { 
            //获取数据绑定器工厂，见8.2.1
            WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
            //获取模型工厂，见8.2.2
            ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);
    
            //扩展HandlerMethod，使其支持处理方法返回值，见8.2.3
            ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
            //参数解析器
            if (this.argumentResolvers != null) { 
                invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
            }
            //返回值处理器
            if (this.returnValueHandlers != null) { 
                invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
            }
            invocableMethod.setDataBinderFactory(binderFactory);
            invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
    
            //创建模型视图容器,见15
            ModelAndViewContainer mavContainer = new ModelAndViewContainer();
            /** * RequestContextUtils.getInputFlashMap(request)方法会得到 * org.springframework.web.servlet.DispatcherServlet.INPUT_FLASH_MAP * 中的域属性值，见15.1 * 而addAllAttributes()方法则会将上面得到的域属性值保存到模型中，见15.2 */
            mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
            //初始化模型，见14.3
            modelFactory.initModel(webRequest, mavContainer, invocableMethod);
            //设置忽略重定向时的默认模型
            mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
    
            /***************************异步web请求start*********************************/
            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);
            }
            /*****************************end***************************************/
    
            /** * 执行处理器方法和处理返回值 * * 这里面又是一大段的逻辑，我们放到下一篇文章讲解 * 见springmvc--5--ServletInvocableHandlerMethod增强的处理器方法 */
            invocableMethod.invokeAndHandle(webRequest, mavContainer);
            if (asyncManager.isConcurrentHandlingStarted()) { 
                return null;
            }
    
            //获取ModelAndView对象，见8.2.4
            return getModelAndView(mavContainer, modelFactory, webRequest);
        }
        finally { 
            //设置请求已处理完成，见11.1
            webRequest.requestCompleted();
        }
    }

> 该方法是核心方法，它会完成请求处理的大部分工作
> 
>  *  创建数据绑定器工厂（解析`@InitBinder`注解）
>  *  创建模型工厂（解析`@ModelAttribute`注解）
>  *  解析`@SessionAttributes`注解
>  *  解析处理器方法参数
>  *  调用处理器方法
>  *  解析处理器方法的返回值
>  *  创建对应的`ModelAndView`对象

### 8.2.1 `getDataBinderFactory(handlerMethod)`方法， 获取数据绑定器工厂 ###

//缓存有@InitBinder注解的方法
 private final Map<Class<?>, Set<Method>> initBinderCache = new ConcurrentHashMap<>(84);
 
 //方法过滤器，过滤得到有@InitBinder注解的方法
 public static final MethodFilter INIT_BINDER_METHODS = method ->
 AnnotatedElementUtils.hasAnnotation(method, InitBinder.class);
 
 /** * 全局方法，实际上就是@ControllerAdvice注解类中有@InitBinder注解的方法， * 见5.1，搜索容器中@ControllerAdvice注解类中有@InitBinder注解的方法 * 这种方式配置数据绑定器对所有的处理器方法生效 */
 private final Map<ControllerAdviceBean, Set<Method>> initBinderAdviceCache = new LinkedHashMap<>();
 
 
 private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) throws Exception { 
 //获取处理器方法所在类的clazz对象
 Class<?> handlerType = handlerMethod.getBeanType();
 //先从缓存中获取该类拥有@InitBinder注解的方法对象
 Set<Method> methods = this.initBinderCache.get(handlerType);
 //第一次，使用内省得到所有有@InitBinder注解的方法，并放入缓存中
 if (methods == null) { 
 methods = MethodIntrospector.selectMethods(handlerType, INIT_BINDER_METHODS);
 this.initBinderCache.put(handlerType, methods);
 }
 
 List<InvocableHandlerMethod> initBinderMethods = new ArrayList<>();
 // Global methods first
 //首先是全局@InitBinder注解方法，遍历
 this.initBinderAdviceCache.forEach((controllerAdviceBean, methodSet) -> { 
 //判断@ControllerAdvice中的方法是否对该处理器方法生效，见9.3
 if (controllerAdviceBean.isApplicableToBeanType(handlerType)) { 
 //获取ControllerAdviceBean对应的bean对象，见9.4
 Object bean = controllerAdviceBean.resolveBean();
 for (Method method : methodSet) { 
 //创建并初始化一个绑定器方法，见8.2.1.1
 initBinderMethods.add(createInitBinderMethod(bean, method));
 }
 }
 });
 
 //其次是拥有@InitBinder注解的方法
 for (Method method : methods) { 
 //获取处理器方法所在类的对象
 Object bean = handlerMethod.getBean();
 //创建并初始化一个绑定器方法，见8.2.1.1
 initBinderMethods.add(createInitBinderMethod(bean, method));
 }
 //创建数据绑定工厂，见8.2.1.2
 return createDataBinderFactory(initBinderMethods);
 }

> 总结：
> 
>  *  首先将全局`@InitBinder`注解方法和其所在类对象封装为`InvocableHandlerMethod`
>  *  接下来将当前处理器方法所在类对象和这个对象中的`@InitBinder`注解方法封装为`InvocableHandlerMethod`
>  *  根据这些`InvocableHandlerMethod`构建一个`ServletRequestDataBinderFactory`工厂对象，用来创建`ServletRequestDataBinder`数据绑定器对象

#### 8.2.1.1 创建并初始化一个绑定器方法`InvocableHandlerMethod` ####

//默认的参数名发现器
 private ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();
 
 /** * 默认为ConfigurableWebBindingInitializer * springmvc配置文件中使用`<mvc:annotation-driven>`，会自动向该属性中填充一个对象 */
 @Nullable
 private WebBindingInitializer webBindingInitializer;
 
 
 private InvocableHandlerMethod createInitBinderMethod(Object bean, Method method) { 
 /** * 可调用的处理器方法，扩展了HandlerMethod * 添加了解析处理器方法参数和数据绑定器工厂的功能 */
 InvocableHandlerMethod binderMethod = new InvocableHandlerMethod(bean, method);
 /** * 设置绑定器的参数解析器 * 类型为HandlerMethodArgumentResolverComposite */
 if (this.initBinderArgumentResolvers != null) { 
 binderMethod.setHandlerMethodArgumentResolvers(this.initBinderArgumentResolvers);
 }
 /** * 设置数据绑定器工厂 * 类型为DefaultDataBinderFactory */
 binderMethod.setDataBinderFactory(new DefaultDataBinderFactory(this.webBindingInitializer));
 //设置参数名发现器
 binderMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
 return binderMethod;
 }

#### 8.2.1.2 创建数据绑定器工厂`ServletRequestDataBinderFactory` ####

/** * Template method to create a new InitBinderDataBinderFactory instance. * The default implementation creates a ServletRequestDataBinderFactory. * This can be overridden for custom ServletRequestDataBinder subclasses. * @param binderMethods {@code @InitBinder} methods * @return the InitBinderDataBinderFactory instance to use * @throws Exception in case of invalid state or arguments */
 protected InitBinderDataBinderFactory createDataBinderFactory(List<InvocableHandlerMethod> binderMethods)
 throws Exception { 
 
 //具体的构造过程见12.1
 return new ServletRequestDataBinderFactory(binderMethods, getWebBindingInitializer());
 }

### 8.2.2 `getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory)`方法，获取模型工厂 ###

//缓存controller中没有@RequestMapping注解且有@ModelAttribute注解的方法列表
 private final Map<Class<?>, Set<Method>> modelAttributeCache = new ConcurrentHashMap<>(64);
 
 //过滤得到没有@RequestMapping注解且有@ModelAttribute注解的方法
 public static final MethodFilter MODEL_ATTRIBUTE_METHODS = method ->
 (!AnnotatedElementUtils.hasAnnotation(method, RequestMapping.class) &&
 AnnotatedElementUtils.hasAnnotation(method, ModelAttribute.class));
 
 
 private ModelFactory getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory) { 
 //获取session属性处理器，见8.2.2.1
 SessionAttributesHandler sessionAttrHandler = getSessionAttributesHandler(handlerMethod);
 //获取处理器方法所在类的clazz对象
 Class<?> handlerType = handlerMethod.getBeanType();
 //下面实际上就是得到有特定条件的方法，并缓存
 Set<Method> methods = this.modelAttributeCache.get(handlerType);
 if (methods == null) { 
 methods = MethodIntrospector.selectMethods(handlerType, MODEL_ATTRIBUTE_METHODS);
 //缓存
 this.modelAttributeCache.put(handlerType, methods);
 }
 List<InvocableHandlerMethod> attrMethods = new ArrayList<>();
 // Global methods first
 //全局方法 @ControllerAdvice注解中的方法
 this.modelAttributeAdviceCache.forEach((controllerAdviceBean, methodSet) -> { 
 if (controllerAdviceBean.isApplicableToBeanType(handlerType)) { 
 Object bean = controllerAdviceBean.resolveBean();
 for (Method method : methodSet) { 
 //创建并初始化一个模型属性方法，见8.2.2.2
 attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
 }
 }
 });
 //当前处理器方法所在类中的方法
 for (Method method : methods) { 
 Object bean = handlerMethod.getBean();
 //创建并初始化一个模型属性方法，见8.2.2.2
 attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
 }
 //创建模型工厂，见14.2
 return new ModelFactory(attrMethods, binderFactory, sessionAttrHandler);
 }

> 总结该方法的流程大致如下所示：
> 
>  *  首先得到当前处理器方法所在类的会话属性处理器`SessionAttributesHandler`
>  *  得到当前处理器方法所在类中没有`@RequestMapping`注解且有`@ModelAttribute`注解的方法列表
>  *  创建并初始化一个模型属性方法（再次封装方法列表中的每一个方法）
>  *  创建模型工厂对象

#### 8.2.2.1 获取`session属性处理器` ####

/** * session属性处理器缓存 * 保存了每一个controller中@SessionAttributes注解信息 */
 private final Map<Class<?>, SessionAttributesHandler> sessionAttributesHandlerCache = new ConcurrentHashMap<>(64);
 
 //session属性操作策略
 private SessionAttributeStore sessionAttributeStore = new DefaultSessionAttributeStore();
 
 
 /** * Return the {@link SessionAttributesHandler} instance for the given handler type * (never {@code null}). */
 private SessionAttributesHandler getSessionAttributesHandler(HandlerMethod handlerMethod) { 
 
 //是以controller的clazz对象为键存储的
 return this.sessionAttributesHandlerCache.computeIfAbsent(
 handlerMethod.getBeanType(),
 type -> new SessionAttributesHandler(type, this.sessionAttributeStore));
 }

#### 8.2.2.2 创建并初始化一个模型属性方法`InvocableHandlerMethod` ####

private InvocableHandlerMethod createModelAttributeMethod(WebDataBinderFactory factory, Object bean, Method method) { 
        InvocableHandlerMethod attrMethod = new InvocableHandlerMethod(bean, method);
        /** * 设置模型属性方法的参数解析器 * 类型为HandlerMethodArgumentResolverComposite */
        if (this.argumentResolvers != null) { 
            attrMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
        }
        /** * 设置模型属性方法的参数名发现器 * 类型为DefaultParameterNameDiscoverer */
        attrMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
        /** * 设置模型属性方法的数据绑定器工厂 * 类型为ServletRequestDataBinderFactory，见8.2.1.2 */
        attrMethod.setDataBinderFactory(factory);
        return attrMethod;
    }

### 8.2.3 创建`ServletInvocableHandlerMethod` ###

/** * Create a {@link ServletInvocableHandlerMethod} from the given {@link HandlerMethod} definition. * @param handlerMethod the {@link HandlerMethod} definition * @return the corresponding {@link ServletInvocableHandlerMethod} (or custom subclass thereof) * @since 4.2 */
    protected ServletInvocableHandlerMethod createInvocableHandlerMethod(HandlerMethod handlerMethod) { 
        return new ServletInvocableHandlerMethod(handlerMethod);
    }

> 只是简单的将`HandlerMethod`处理器方法包装为一个`web`环境的处理器方法`ServletInvocableHandlerMethod`

### 8.2.4 获取`ModelAndView`对象 ###

@Nullable
 private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
 ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception { 
 
 /** * 将模型中与用户通过@SessionAttributes注解声明的匹配的属性存储到session域中 * 有必要的话就将数据绑定属性保存到模型中，见14.6 */
 modelFactory.updateModel(webRequest, mavContainer);
 //请求已被完全处理
 if (mavContainer.isRequestHandled()) { 
 return null;
 }
 /** * 获取当前使用的模型，见15.2 * 重定向使用重定向模型，否则使用默认模型 */
 ModelMap model = mavContainer.getModel();
 //初始化一个ModelAndView对象，见16.1
 ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
 //非视图名，即视图对象
 if (!mavContainer.isViewReference()) { 
 //强转为视图对象并设置到ModelAndView中
 mav.setView((View) mavContainer.getView());
 }
 
 //重定向
 if (model instanceof RedirectAttributes) { 
 Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();
 HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
 if (request != null) { 
 RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
 }
 }
 return mav;
 }

>  *  对于需要响应视图的请求，在此方法中会创建一个`ModelAndView`对象，同时保存模型数据，视图和响应状态
>  *  对于不需要响应视图的请求，比如有`@ResponseBody`注解，就直接返回`null`

# 9 `ControllerAdviceBean`类，封装`@ControllerAdvice`注解的`bean` #

下面是属性

public class ControllerAdviceBean implements Ordered { 
 
 /** * Reference to the actual bean instance or a {@code String} representing * the bean name. */
 private final Object beanOrName;
 
 private final boolean isSingleton;
 
 /** * Reference to the resolved bean instance, potentially lazily retrieved * via the {@code BeanFactory}. */
 @Nullable
 private Object resolvedBean;
 
 @Nullable
 private final Class<?> beanType;
 
 private final HandlerTypePredicate beanTypePredicate;
 
 @Nullable
 private final BeanFactory beanFactory;
 
 @Nullable
 private Integer order;
 }

## 9.1 构造方法 ##

/** * Create a {@code ControllerAdviceBean} using the given bean name, * {@code BeanFactory}, and {@link ControllerAdvice @ControllerAdvice} * annotation. * @param beanName the name of the bean * @param beanFactory a {@code BeanFactory} to retrieve the bean type initially * and later to resolve the actual bean * @param controllerAdvice the {@code @ControllerAdvice} annotation for the * bean, or {@code null} if not yet retrieved * @since 5.2 */
    public ControllerAdviceBean(String beanName, BeanFactory beanFactory, @Nullable ControllerAdvice controllerAdvice) { 
        Assert.hasText(beanName, "Bean name must contain text");
        Assert.notNull(beanFactory, "BeanFactory must not be null");
        Assert.isTrue(beanFactory.containsBean(beanName), () -> "BeanFactory [" + beanFactory +
                      "] does not contain specified controller advice bean '" + beanName + "'");
        //保存beanName
        this.beanOrName = beanName;
        //是否单例
        this.isSingleton = beanFactory.isSingleton(beanName);
        //bean的类型
        this.beanType = getBeanType(beanName, beanFactory);
        //bean对象类型断言
        this.beanTypePredicate = (controllerAdvice != null ? createBeanTypePredicate(controllerAdvice) :
                                  createBeanTypePredicate(this.beanType));
        this.beanFactory = beanFactory;
    }
    
    //根据@ControllerAdvice注解信息构建一个HandlerTypePredicate
    private static HandlerTypePredicate createBeanTypePredicate(@Nullable ControllerAdvice controllerAdvice) { 
        if (controllerAdvice != null) { 
            return HandlerTypePredicate.builder()
                .basePackage(controllerAdvice.basePackages())
                .basePackageClass(controllerAdvice.basePackageClasses())
                .assignableType(controllerAdvice.assignableTypes())
                .annotation(controllerAdvice.annotations())
                .build();
        }
        return HandlerTypePredicate.forAnyHandlerType();
    }

> 该构造方法解析得到`@ControllerAdvice`注解的`bean`的名字和类型，并创建对应的`HandlerTypePredicate`

## 9.2 获取容器中有`@ControllerAdvice`注解的`bean`，并封装为`ControllerAdviceBean` ##

/** * Find beans annotated with {@link ControllerAdvice @ControllerAdvice} in the * given {@link ApplicationContext} and wrap them as {@code ControllerAdviceBean} * instances. * As of Spring Framework 5.2, the {@code ControllerAdviceBean} instances * in the returned list are sorted using {@link OrderComparator#sort(List)}. * @see #getOrder() * @see OrderComparator * @see Ordered */
 public static List<ControllerAdviceBean> findAnnotatedBeans(ApplicationContext context) { 
 List<ControllerAdviceBean> adviceBeans = new ArrayList<>();
 //获取容器中所有bean的名字并遍历
 for (String name : BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context, Object.class)) { 
 //非代理类（没有使用作用域代理模式，@Scope注解指定）
 if (!ScopedProxyUtils.isScopedTarget(name)) { 
 //得到bean中@ControllerAdvice注解信息
 ControllerAdvice controllerAdvice = context.findAnnotationOnBean(name, ControllerAdvice.class);
 //有@ControllerAdvice注解
 if (controllerAdvice != null) { 
 // Use the @ControllerAdvice annotation found by findAnnotationOnBean()
 // in order to avoid a subsequent lookup of the same annotation.
 //构建ControllerAdviceBean，见9.1
 adviceBeans.add(new ControllerAdviceBean(name, context, controllerAdvice));
 }
 }
 }
 //根据PriorityOrdered接口和Order接口排序
 OrderComparator.sort(adviceBeans);
 return adviceBeans;
 }

> 该方法会获取到容器中所有`@ControllerAdvice`注解的`bean`，并封装为`ControllerAdviceBean`，然后根据`PriorityOrdered`接口和`Order`接口排序。

## 9.3 判断`@ControllerAdvice`中的方法是否对该处理器方法所在类生效 ##

/** * Check whether the given bean type should be advised by this * {@code ControllerAdviceBean}. * @param beanType the type of the bean to check * @since 4.0 * @see ControllerAdvice */
 public boolean isApplicableToBeanType(@Nullable Class<?> beanType) { 
 //使用断言器，判断是否对该类生效，见10.2
 return this.beanTypePredicate.test(beanType);
 }

## 9.4 获取`ControllerAdviceBean`对应的`bean`对象 ##

/** * Get the bean instance for this {@code ControllerAdviceBean}, if necessary * resolving the bean name through the {@link BeanFactory}. * As of Spring Framework 5.2, once the bean instance has been resolved it * will be cached if it is a singleton, thereby avoiding repeated lookups in * the {@code BeanFactory}. */
 public Object resolveBean() { 
 if (this.resolvedBean == null) { 
 // this.beanOrName must be a String representing the bean name if
 // this.resolvedBean is null.
 //调用工厂的getBean()方法实例化
 Object resolvedBean = obtainBeanFactory().getBean((String) this.beanOrName);
 // Don't cache non-singletons (e.g., prototypes).
 //非单例的就不缓存
 if (!this.isSingleton) { 
 return resolvedBean;
 }
 //单例的缓存
 this.resolvedBean = resolvedBean;
 }
 return this.resolvedBean;
 }

# 10 `HandlerTypePredicate`，断言器，用来匹配请求处理组件的类型 #

它是专门用来匹配`@ControllerAdvice`注解指定类的一个断言器，它有一个嵌套类`Builder`（建造者模式），方便创建一个`HandlerTypePredicate`对象。

public final class HandlerTypePredicate implements Predicate<Class<?>> { 
 //包名
 private final Set<String> basePackages;
 //类型
 private final List<Class<?>> assignableTypes;
 //注解
 private final List<Class<? extends Annotation>> annotations;
 }

> 很明显，它的三个属性分别对应的`@ControllerAdvice`注解中的三个属性，这`3`个属性用来指定`@ControllerAdvice`注解类中方法的生效类，比如我们常用的`@ExceptionHandler`（全局异常处理器），可以在`ControllerAdvice`注解中指定能够捕获哪些类抛出的异常。
> 
> 并且它实现了`spring`定义的`Predicate`断言接口，所以它的核心方法是`test()`方法。

## 10.1 嵌套类`Builder`（建造者模式） ##

public static class Builder { 
 
 //这三个属性分别对应的@ControllerAdvice注解中的三个 
 private final Set<String> basePackages = new LinkedHashSet<>();
 
 private final List<Class<?>> assignableTypes = new ArrayList<>();
 
 private final List<Class<? extends Annotation>> annotations = new ArrayList<>();
 
 /** * Match handlers declared under a base package, e.g. "org.example". * @param packages one or more base package classes */
 public Builder basePackage(String... packages) { 
 Arrays.stream(packages).filter(StringUtils::hasText).forEach(this::addBasePackage);
 return this;
 }
 
 /** * Type-safe alternative to {@link #forBasePackage(String...)} to specify a * base package through a class. * @param packageClasses one or more base package names */
 public Builder basePackageClass(Class<?>... packageClasses) { 
 Arrays.stream(packageClasses).forEach(clazz -> addBasePackage(ClassUtils.getPackageName(clazz)));
 return this;
 }
 
 private void addBasePackage(String basePackage) { 
 this.basePackages.add(basePackage.endsWith(".") ? basePackage : basePackage + ".");
 }
 
 /** * Match handlers that are assignable to a given type. * @param types one or more handler super types */
 public Builder assignableType(Class<?>... types) { 
 this.assignableTypes.addAll(Arrays.asList(types));
 return this;
 }
 
 /** * Match types that are annotated with one of the given annotations. * @param annotations one or more annotations to check for */
 @SuppressWarnings("unchecked")
 public final Builder annotation(Class<? extends Annotation>... annotations) { 
 this.annotations.addAll(Arrays.asList(annotations));
 return this;
 }
 
 //最后这个build()方法中创建一个HandlerTypePredicate对象
 public HandlerTypePredicate build() { 
 return new HandlerTypePredicate(this.basePackages, this.assignableTypes, this.annotations);
 }
 }

> 这就是`9.1`中使用的一种类似于`Stream`的原理

## 10.2 `test()`方法（`Predicate`断言接口的唯一方法） ##

@Override
 public boolean test(Class<?> controllerType) { 
 /** * 未在@ControllerAdvice注解中指定生效类 * 说明对所有的类都生效 */
 if (!hasSelectors()) { 
 return true;
 }
 
 //部分类生效，进行三种方式的判断
 else if (controllerType != null) { 
 //包名
 for (String basePackage : this.basePackages) { 
 if (controllerType.getName().startsWith(basePackage)) { 
 return true;
 }
 }
 //类型
 for (Class<?> clazz : this.assignableTypes) { 
 if (ClassUtils.isAssignable(clazz, controllerType)) { 
 return true;
 }
 }
 //注解
 for (Class<? extends Annotation> annotationClass : this.annotations) { 
 if (AnnotationUtils.findAnnotation(controllerType, annotationClass) != null) { 
 return true;
 }
 }
 }
 return false;
 }
 
 
 //判断是否配置@ControllerAdvice注解属性
 private boolean hasSelectors() { 
 return (!this.basePackages.isEmpty() || !this.assignableTypes.isEmpty() || !this.annotations.isEmpty());
 }

# 11 `ServletWebRequest`类，适配`HttpServletRequest` #

下面是它的类图

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMDEyOTgx_size_16_color_FFFFFF_t_70_pic_center 1]

我们再来看一下这`3`个接口提供的方法

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMDEyOTgx_size_16_color_FFFFFF_t_70_pic_center 2]

>  *  `RequestAttributes`接口，它提供了对请求域属性操作的方法和获取`Session`信息的相关方法。它的实现类`ServletRequestAttributes`持有一个`HttpServletRequest`、`HttpServletResponse`、`HttpSession`对象，这些接口方法的实现最终是借助原生的`HttpServletRequest`方法实现的。
>  *  `WebRequest`接口，进一步扩展，它提供了很多方法，比如访问请求参数、请求头信息、请求描述、上下文路径，这些都可以通过`HttpServletRequest`对象的原生方法得到
>  *  `NativeWebRequest`接口，提供获取本次请求响应对象的方法，后面两种方法可以获取指定请求响应对象的上级包装对象

下面是`getNativeRequest()`方法内部实现

/** * Return an appropriate request object of the specified type, if available, * unwrapping the given request as far as necessary. * @param request the servlet request to introspect * @param requiredType the desired type of request object * @return the matching request object, or {@code null} if none * of that type is available */
 @SuppressWarnings("unchecked")
 @Nullable
 public static <T> T getNativeRequest(ServletRequest request, @Nullable Class<T> requiredType) { 
 if (requiredType != null) { 
 if (requiredType.isInstance(request)) { 
 return (T) request;
 }
 else if (request instanceof ServletRequestWrapper) { 
 //递归，获取匹配的类型
 return getNativeRequest(((ServletRequestWrapper) request).getRequest(), requiredType);
 }
 }
 return null;
 }

## 11.1 `requestCompleted()`方法，设置请求已完成 ##

> 该方法定义在`AbstractRequestAttributes`类中

//请求是否活跃，完成了就不活跃为false
 private volatile boolean requestActive = true;
 
 /** * Signal that the request has been completed. * Executes all request destruction callbacks and updates the * session attributes that have been accessed during request processing. */
 public void requestCompleted() { 
 executeRequestDestructionCallbacks();
 updateAccessedSessionAttributes();
 //设置本次请求状态为已完成
 this.requestActive = false;
 }

# 12 `WebDataBinderFactory`数据绑定器工厂 #

默认使用的是`ServletRequestDataBinderFactory`，它的类图如下

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMDEyOTgx_size_16_color_FFFFFF_t_70_pic_center 3]

我们看一下`WebDataBinderFactory`接口

public interface WebDataBinderFactory { 
    
        /** * Create a {@link WebDataBinder} for the given object. * @param webRequest the current request * @param target the object to create a data binder for, * or {@code null} if creating a binder for a simple type * @param objectName the name of the target object * @return the created {@link WebDataBinder} instance, never null * @throws Exception raised if the creation and initialization of the data binder fails */
        WebDataBinder createBinder(NativeWebRequest webRequest, @Nullable Object target, String objectName)
            throws Exception;
    
    }

> 很明显，这是一个工厂接口，它用来创建一个`WebDataBinder`数据绑定器对象

## 12.1 `ServletRequestDataBinderFactory`的构造方法 ##

/** * Create a new instance. * @param binderMethods one or more {@code @InitBinder} methods * @param initializer provides global data binder initialization */
 public ServletRequestDataBinderFactory(@Nullable List<InvocableHandlerMethod> binderMethods,
 @Nullable WebBindingInitializer initializer) { 
 
 super(binderMethods, initializer);
 }

父类`InitBinderDataBinderFactory`构造方法

//保存有@InitBinder注解的方法
 private final List<InvocableHandlerMethod> binderMethods;
 
 /** * Create a new InitBinderDataBinderFactory instance. * @param binderMethods {@code @InitBinder} methods * @param initializer for global data binder initialization */
 public InitBinderDataBinderFactory(@Nullable List<InvocableHandlerMethod> binderMethods,
 @Nullable WebBindingInitializer initializer) { 
 
 super(initializer);
 this.binderMethods = (binderMethods != null ? binderMethods : Collections.emptyList());
 }

父类`DefaultDataBinderFactory`构造方法

/** * 绑定器的初始化器 * 使用这个初始化器来初始化绑定器 */
    @Nullable
    private final WebBindingInitializer initializer;
    
    
    /** * Create a new {@code DefaultDataBinderFactory} instance. * @param initializer for global data binder initialization * (or {@code null} if none) */
    public DefaultDataBinderFactory(@Nullable WebBindingInitializer initializer) { 
       this.initializer = initializer;
    }

> 构造方法只是简单的将两个参数对象赋值给属性

## 12.2 `createBinder(NativeWebRequest webRequest, @Nullable Object target, String objectName)`方法，创建属性对应的数据绑定器 ##

/** * Create a new {@link WebDataBinder} for the given target object and * initialize it through a {@link WebBindingInitializer}. * @throws Exception in case of invalid state or arguments */
    @Override
    @SuppressWarnings("deprecation")
    public final WebDataBinder createBinder(
        NativeWebRequest webRequest, @Nullable Object target, String objectName) throws Exception { 
    
        //创建数据绑定器实例，类型为ExtendedServletRequestDataBinder
        WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest);
        //初始化器初始化数据绑定器
        if (this.initializer != null) { 
            this.initializer.initBinder(dataBinder, webRequest);
        }
        //初始化数据绑定器
        initBinder(dataBinder, webRequest);
        return dataBinder;
    }

# 13 `SessionAttributesHandler` 会话属性处理器 #

> 管理`@SessionAttributes`注解声明的属性，实际过程委派给`SessionAttributeStore`实例完成

下面是`SessionAttributesHandler`类的属性

public class SessionAttributesHandler { 
 
 //session属性名
 private final Set<String> attributeNames = new HashSet<>();
 
 //session属性类型
 private final Set<Class<?>> attributeTypes = new HashSet<>();
 
 //已知的属性名
 private final Set<String> knownAttributeNames = Collections.newSetFromMap(new ConcurrentHashMap<>(4));
 
 //session属性存储策略
 private final SessionAttributeStore sessionAttributeStore;
 }

## 13.1 `SessionAttributeStore`策略接口，定义操作`session域属性`的规范 ##

public interface SessionAttributeStore { 
    
        /** * 存储属性要session域中 * @param request 当前请求 * @param attributeName 属性名 * @param attributeValue 属性值 */
        void storeAttribute(WebRequest request, String attributeName, Object attributeValue);
    
        /** * 获取session域attributeName对应属性值 */
        @Nullable
        Object retrieveAttribute(WebRequest request, String attributeName);
    
        /** * 清除session域attributeName对应属性 */
        void cleanupAttribute(WebRequest request, String attributeName);
    
    }

> 很明显，这个接口定义了操作`session域属性`的规范，策略模式主要是为了解耦。我们可以看一下`springmvc`对该接口的默认实现

@Override
    public void storeAttribute(WebRequest request, String attributeName, Object attributeValue) { 
        Assert.notNull(request, "WebRequest must not be null");
        Assert.notNull(attributeName, "Attribute name must not be null");
        Assert.notNull(attributeValue, "Attribute value must not be null");
        String storeAttributeName = getAttributeNameInSession(request, attributeName);
        //最终借助了原生request的setAttribute()方法，完成session属性存储
        request.setAttribute(storeAttributeName, attributeValue, WebRequest.SCOPE_SESSION);
    }
    
    @Override
    @Nullable
    public Object retrieveAttribute(WebRequest request, String attributeName) { 
        Assert.notNull(request, "WebRequest must not be null");
        Assert.notNull(attributeName, "Attribute name must not be null");
        String storeAttributeName = getAttributeNameInSession(request, attributeName);
         //最终借助了原生request的getAttribute()方法，完成session属性获取
        return request.getAttribute(storeAttributeName, WebRequest.SCOPE_SESSION);
    }

## 13.2 `SessionAttributesHandler`的构造方法 ##

/** * Create a new session attributes handler. Session attribute names and types * are extracted from the {@code @SessionAttributes} annotation, if present, * on the given type. * @param handlerType the controller type * @param sessionAttributeStore used for session access */
 public SessionAttributesHandler(Class<?> handlerType, SessionAttributeStore sessionAttributeStore) { 
 Assert.notNull(sessionAttributeStore, "SessionAttributeStore may not be null");
 this.sessionAttributeStore = sessionAttributeStore;
 
 //找到处理器方法所在类上@SessionAttributes注解信息
 SessionAttributes ann = AnnotatedElementUtils.findMergedAnnotation(handlerType, SessionAttributes.class);
 //将注解上的属性信息保存到会话属性处理器中
 if (ann != null) { 
 Collections.addAll(this.attributeNames, ann.names());
 Collections.addAll(this.attributeTypes, ann.types());
 }
 this.knownAttributeNames.addAll(this.attributeNames);
 }

>  *  构造方法会获取到对应类上的`@SessionAttributes`注解信息，然后将用户设置在注解上的信息保存到`SessionAttributesHandler`会话属性处理器中。
>  *  `@SessionAttributes`注解是用来声明`session`域中必须存在的属性。

## 13.3 `retrieveAttributes(WebRequest request)`方法，得到`session`中的已知属性的值 ##

/** * Retrieve "known" attributes from the session, i.e. attributes listed * by name in {@code @SessionAttributes} or attributes previously stored * in the model that matched by type. * @param request the current request * @return a map with handler session attributes, possibly empty */
 public Map<String, Object> retrieveAttributes(WebRequest request) { 
 Map<String, Object> attributes = new HashMap<>();
 for (String name : this.knownAttributeNames) { 
 Object value = this.sessionAttributeStore.retrieveAttribute(request, name);
 if (value != null) { 
 attributes.put(name, value);
 }
 }
 return attributes;
 }

> 该方法会得到`@SessionAttributes`注解声明的`session`域属性键值对。

## 13.4 `isHandlerSessionAttribute(String attributeName, Class<?> attributeType)`方法，判断属性名称或属性类型是否与用户通过`@SessionAttributes`注解指定的属性匹配 ##

/** * Whether the attribute name or type match the names and types specified * via {@code @SessionAttributes} on the underlying controller. * Attributes successfully resolved through this method are "remembered" * and subsequently used in {@link #retrieveAttributes(WebRequest)} and * {@link #cleanupAttributes(WebRequest)}. * @param attributeName the attribute name to check * @param attributeType the type for the attribute */
 public boolean isHandlerSessionAttribute(String attributeName, Class<?> attributeType) { 
 Assert.notNull(attributeName, "Attribute name must not be null");
 //属性名或属性类型
 if (this.attributeNames.contains(attributeName) || this.attributeTypes.contains(attributeType)) { 
 this.knownAttributeNames.add(attributeName);
 return true;
 }
 else { 
 return false;
 }
 }

> 判断属性名称或属性类型是否与用户通过`@SessionAttributes`注解指定的属性匹配

## 13.5 `cleanupAttributes(WebRequest request)`方法，清理会话属性 ##

/** * Remove "known" attributes from the session, i.e. attributes listed * by name in {@code @SessionAttributes} or attributes previously stored * in the model that matched by type. * @param request the current request */
    public void cleanupAttributes(WebRequest request) { 
       for (String attributeName : this.knownAttributeNames) { 
          this.sessionAttributeStore.cleanupAttribute(request, attributeName);
       }
    }

> 删除所有`@SessionAttributes`注解声明的`session`域属性

## 13.6 `storeAttributes(WebRequest request, Map<String, ?> attributes)`方法，将模型中与用户`@SessionAttributes`注解声明的匹配的属性存储到`session`域中 ##

/** * Store a subset of the given attributes in the session. Attributes not * declared as session attributes via {@code @SessionAttributes} are ignored. * @param request the current request * @param attributes candidate attributes for session storage */
 public void storeAttributes(WebRequest request, Map<String, ?> attributes) { 
 attributes.forEach((name, value) -> { 
 //存储之前会过滤
 if (value != null && isHandlerSessionAttribute(name, value.getClass())) { 
 this.sessionAttributeStore.storeAttribute(request, name, value);
 }
 });
 }

> 只会将模型中与用户通过`@SessionAttributes`注解声明的匹配的属性存储到`session`域中

# 14 `ModelFactory`模型工厂 #

> 作用：
> 
>  *  在控制器方法调用之前初始化`Model`，会将`@ModelAttribute`注解指定属性保存到`Model`中
>  *  在控制器方法调用之后更新`Model`数据

首先看一下它的属性

public final class ModelFactory { 
 
 //模型方法
 private final List<ModelMethod> modelMethods = new ArrayList<>();
 
 //数据绑定器工厂
 private final WebDataBinderFactory dataBinderFactory;
 
 //session属性处理器
 private final SessionAttributesHandler sessionAttributesHandler;
 }

## 14.1 `ModelMethod` 模型方法 ##

> 该类是`ModelFactory`的嵌套类

private static class ModelMethod { 
 
 //模型属性方法
 private final InvocableHandlerMethod handlerMethod;
 
 //@ModelAttribute注解标注的参数名
 private final Set<String> dependencies = new HashSet<>();
 
 public ModelMethod(InvocableHandlerMethod handlerMethod) { 
 this.handlerMethod = handlerMethod;
 /** * 遍历模型属性方法的参数 * 参数上有@ModelAttribute注解就将参数名保存到dependencies属性中 */
 for (MethodParameter parameter : handlerMethod.getMethodParameters()) { 
 if (parameter.hasParameterAnnotation(ModelAttribute.class)) { 
 this.dependencies.add(getNameForParameter(parameter));
 }
 }
 }
 
 public InvocableHandlerMethod getHandlerMethod() { 
 return this.handlerMethod;
 }
 
 //判断视图模型容器中是否存在@ModelAttribute注解标注的参数名
 public boolean checkDependencies(ModelAndViewContainer mavContainer) { 
 for (String name : this.dependencies) { 
 if (!mavContainer.containsAttribute(name)) { 
 return false;
 }
 }
 return true;
 }
 
 @Override
 public String toString() { 
 return this.handlerMethod.getMethod().toGenericString();
 }
 }

> `@ModelAttribute`既可以标注在`方法`上又可以标注在`方法参数`上
> 
> 该类会对在方法上标注`@ModelAttribute`注解的方法进行初步处理，它会将方法参数中有`@ModelAttribute`注解的参数名解析并封装到属性中

## 14.2 构造方法 ##

/** * Create a new instance with the given {@code @ModelAttribute} methods. * @param handlerMethods the {@code @ModelAttribute} methods to invoke * @param binderFactory for preparation of {@link BindingResult} attributes * @param attributeHandler for access to session attributes */
 public ModelFactory(@Nullable List<InvocableHandlerMethod> handlerMethods,
 WebDataBinderFactory binderFactory, SessionAttributesHandler attributeHandler) { 
 
 if (handlerMethods != null) { 
 for (InvocableHandlerMethod handlerMethod : handlerMethods) { 
 this.modelMethods.add(new ModelMethod(handlerMethod));
 }
 }
 this.dataBinderFactory = binderFactory;
 this.sessionAttributesHandler = attributeHandler;
 }

> 构造方法没做什么事情，只是简单的为`@ModelAttribute`注解方法创建一个`ModelMethod`方法实例，另外给其他属性初始化一些值

## 14.3 `initModel(NativeWebRequest request, ModelAndViewContainer container, HandlerMethod handlerMethod)`方法，初始化模型 ##

/** * Populate the model in the following order: * <ol> * <li>Retrieve "known" session attributes listed as {@code @SessionAttributes}. * <li>Invoke {@code @ModelAttribute} methods * <li>Find {@code @ModelAttribute} method arguments also listed as * {@code @SessionAttributes} and ensure they're present in the model raising * an exception if necessary. * </ol> * @param request the current request * @param container a container with the model to be initialized * @param handlerMethod the method for which the model is initialized * @throws Exception may arise from {@code @ModelAttribute} methods */
 public void initModel(NativeWebRequest request, ModelAndViewContainer container, HandlerMethod handlerMethod)
 throws Exception { 
 
 //得到@SessionAttributes注解声明的所有session域属性键值对，见13.3
 Map<String, ?> sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
 /** * 合并模型数据，见15.3 * 合并request和session域属性，之前在15.1中得到了特定的request域属性 * 现在在13.3中有得到了所有@SessionAttributes注解声明的所有session域属性 * 在此处进行两个的合并 */
 container.mergeAttributes(sessionAttributes);
 //执行模型属性方法，见14.4
 invokeModelAttributeMethods(request, container);
 
 
 //获取模型方法所有中Session属性参数名
 for (String name : findSessionAttributeArguments(handlerMethod)) { 
 //模型视图容器中不包含该参数名
 if (!container.containsAttribute(name)) { 
 //取得参数名对应的session属性值
 Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
 if (value == null) { 
 throw new HttpSessionRequiredException("Expected session attribute '" + name + "'", name);
 }
 //保存到模型视图容器中
 container.addAttribute(name, value);
 }
 }
 }

> 该方法主要作用是填充模型属性，按如下顺序
> 
>  *  `@SessionAttributes`注解声明的所有`session域属性`
>  *  模型属性方法的返回值
>  *  模型方法中所有匹配`@SessionAttributes`注解声明的属性的标注`@ModelAttribute`注解参数

## 14.4 `invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer container)`方法，执行模型属性方法 ##

/** * Invoke model attribute methods to populate the model. * Attributes are added only if not already present in the model. */
    private void invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer container)
        throws Exception { 
    
        //遍历执行所有@ModelAttribute注解方法（包括全局的）
        while (!this.modelMethods.isEmpty()) { 
            //顺序获取模型方法
            InvocableHandlerMethod modelMethod = getNextModelMethod(container).getHandlerMethod();
            //得到方法上的@ModelAttribute注解信息
            ModelAttribute ann = modelMethod.getMethodAnnotation(ModelAttribute.class);
            Assert.state(ann != null, "No ModelAttribute annotation");
            //模型视图容器中包含用户在的@ModelAttribute注解name属性指定的名字
            if (container.containsAttribute(ann.name())) { 
                //@ModelAttribute注解上声明关闭数据绑定
                if (!ann.binding()) { 
                    //@ModelAttribute注解上声明的所有属性都禁用数据绑定
                    container.setBindingDisabled(ann.name());
                }
                continue;
            }
    
            //执行模型方法，见14.4.2
            Object returnValue = modelMethod.invokeForRequest(request, container);
            //模型方法有返回值
            if (!modelMethod.isVoid()){ 
                //获取方法返回值的名字，见14.4.3
                String returnValueName = getNameForReturnValue(returnValue, modelMethod.getReturnType());
                //该返回值禁用数据绑定
                if (!ann.binding()) { 
                    container.setBindingDisabled(returnValueName);
                }
                //返回值保存到模型中
                if (!container.containsAttribute(returnValueName)) { 
                    container.addAttribute(returnValueName, returnValue);
                }
            }
        }
    }

### 14.4.1 顺序获取模型方法 ###

private ModelMethod getNextModelMethod(ModelAndViewContainer container) { 
        for (ModelMethod modelMethod : this.modelMethods) { 
            /** * checkDependencies(container)方法见14.1 * 会把模型方法参数上有@ModelAttribute注解的参数和视图模型容器中的属性一一比较 * 只要有一个标注了@ModelAttribute注解的参数在视图模型容器中找不到同名属性，就返回false * 说明该模型方法还未执行过，需要执行. * 否则返回true，从列表中移除该标注了@ModelAttribute注解的方法 */
            if (modelMethod.checkDependencies(container)) { 
                this.modelMethods.remove(modelMethod);
                return modelMethod;
            }
        }
        
        //按顺序获取模型方法
        ModelMethod modelMethod = this.modelMethods.get(0);
        this.modelMethods.remove(modelMethod);
        return modelMethod;
    }

> 它会先检查所有模型方法，如果发现这样一个方法（所有标注了`@ModelAttribute`注解的参数都能在视图模型容器中找同名属性），就删掉方法缓存，然后返回该方法对象。
> 
> 否则按照顺序获取模型工厂中的模型方法。

### 14.4.2 执行模型方法 ###

/** * Invoke the method after resolving its argument values in the context of the given request. * Argument values are commonly resolved through * {@link HandlerMethodArgumentResolver HandlerMethodArgumentResolvers}. * The {@code providedArgs} parameter however may supply argument values to be used directly, * i.e. without argument resolution. Examples of provided argument values include a * {@link WebDataBinder}, a {@link SessionStatus}, or a thrown exception instance. * Provided argument values are checked before argument resolvers. * Delegates to {@link #getMethodArgumentValues} and calls {@link #doInvoke} with the * resolved arguments. * @param request the current request * @param mavContainer the ModelAndViewContainer for this request * @param providedArgs "given" arguments matched by type, not resolved * @return the raw value returned by the invoked method * @throws Exception raised if no suitable argument resolver can be found, * or if the method raised an exception * @see #getMethodArgumentValues * @see #doInvoke */
 @Nullable
 public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
 Object... providedArgs) throws Exception { 
 
 Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
 if (logger.isTraceEnabled()) { 
 logger.trace("Arguments: " + Arrays.toString(args));
 }
 return doInvoke(args);
 }

> 该方法的源码我们放到下一篇文章再看（`springmvc--5--ServletInvocableHandlerMethod增强的处理器方法`）
> 
> 我先来简单说一下过程：首先一个一个的解析方法参数，解析时遍历我们在`5.2`中设置的默认的参数解析器，找到第一个能解析方法参数的解析器，进行解析方法参数，得到参数值。所有参数解析成功后使用反射`invoke()`方法完成方法调用。

### 14.4.3 获取方法返回值的名字 ###

/** * Derive the model attribute name for the given return value. Results will be * based on: * <ol> * <li>the method {@code ModelAttribute} annotation value * <li>the declared return type if it is more specific than {@code Object} * <li>the actual return value type * </ol> * @param returnValue the value returned from a method invocation * @param returnType a descriptor for the return type of the method * @return the derived name (never {@code null} or empty String) */
 public static String getNameForReturnValue(@Nullable Object returnValue, MethodParameter returnType) { 
 //获取模型方法上的@ModelAttribute注解信息
 ModelAttribute ann = returnType.getMethodAnnotation(ModelAttribute.class);
 /** * 有@ModelAttribute注解且指定了返回值的存储名 * 以@ModelAttribute注解的value属性为key，保存模型方法的返回到模型中 */
 if (ann != null && StringUtils.hasText(ann.value())) { 
 return ann.value();
 }
 //使用默认的名字将返回值保存到模型中
 else { 
 Method method = returnType.getMethod();
 Assert.state(method != null, "No handler method");
 Class<?> containingClass = returnType.getContainingClass();
 Class<?> resolvedType = GenericTypeResolver.resolveReturnType(method, containingClass);
 return Conventions.getVariableNameForReturnType(method, resolvedType, returnValue);
 }
 }

## 14.5 `findSessionAttributeArguments(HandlerMethod handlerMethod)`方法，获取模型方法所有中`Session属性`参数名 ##

/** * Find {@code @ModelAttribute} arguments also listed as {@code @SessionAttributes}. */
 private List<String> findSessionAttributeArguments(HandlerMethod handlerMethod) { 
 List<String> result = new ArrayList<>();
 //遍历模型方法参数
 for (MethodParameter parameter : handlerMethod.getMethodParameters()) { 
 //参数上有@ModelAttribute注解
 if (parameter.hasParameterAnnotation(ModelAttribute.class)) { 
 //参数名
 String name = getNameForParameter(parameter);
 //参数类型
 Class<?> paramType = parameter.getParameterType();
 //参数是@SessionAttributes注解指定的属性
 if (this.sessionAttributesHandler.isHandlerSessionAttribute(name, paramType)) { 
 result.add(name);
 }
 }
 }
 return result;
 }j

> 该方法会得到模型方法中满足下面条件的参数名
> 
>  *  参数上有`@ModelAttribute`注解
>  *  参数名或类型匹配用户`@SessionAttributes`注解指定的参数名或类型

## 14.6 `updateModel(NativeWebRequest request, ModelAndViewContainer container)`方法， 将`@SessionAttributes`注解声明的属性保存到`session`域 ##

/** * Promote model attributes listed as {@code @SessionAttributes} to the session. * Add {@link BindingResult} attributes where necessary. * @param request the current request * @param container contains the model to update * @throws Exception if creating BindingResult attributes fails */
    public void updateModel(NativeWebRequest request, ModelAndViewContainer container) throws Exception { 
        //得到默认模型，见15.4
        ModelMap defaultModel = container.getDefaultModel();
        //当前会话已完成，见15.5
        if (container.getSessionStatus().isComplete()){ 
            //清理@SessionAttributes注解声明的会话属性，见13.5
            this.sessionAttributesHandler.cleanupAttributes(request);
        }
        //当前会话未完成
        else { 
            //只会将模型中与用户通过@SessionAttributes注解声明的匹配的属性存储到session域中，见13.6
            this.sessionAttributesHandler.storeAttributes(request, defaultModel);
        }
        //请求未被完全处理，且使用默认模型（即非重定向）
        if (!container.isRequestHandled() && container.getModel() == defaultModel) { 
            //将需要数据绑定的属性添加到模型中,见14.7
            updateBindingResult(request, defaultModel);
        }
    }

>  *  该方法会判断会话状态，如果会话已完成，就清理`@SessionAttributes`注解声明的会话属性，否则将将模型中与用户通过`@SessionAttributes`注解声明的匹配的属性存储到`session`域中
>  *  如果非重定向且请求为被完全处理，就将数据绑定的属性添加到模型中

## 14.7 `updateBindingResult(NativeWebRequest request, ModelMap model)`方法，将数据绑定的属性添加到模型中 ##

/** * Add {@link BindingResult} attributes to the model for attributes that require it. */
 private void updateBindingResult(NativeWebRequest request, ModelMap model) throws Exception { 
 List<String> keyNames = new ArrayList<>(model.keySet());
 for (String name : keyNames) { 
 Object value = model.get(name);
 //该属性需要进行数据绑定
 if (value != null && isBindingCandidate(name, value)) { 
 //MODEL_KEY_PREFIX="org.springframework.validation.BindingResult."
 String bindingResultKey = BindingResult.MODEL_KEY_PREFIX + name;
 //模型中不包含该数据绑定属性
 if (!model.containsAttribute(bindingResultKey)) { 
 //使用数据绑定器工厂创建该属性的数据绑定器，见12.2
 WebDataBinder dataBinder = this.dataBinderFactory.createBinder(request, value, name);
 //保存属性
 model.put(bindingResultKey, dataBinder.getBindingResult());
 }
 }
 }
 }
 
 
 /** * Whether the given attribute requires a {@link BindingResult} in the model. */
 private boolean isBindingCandidate(String attributeName, Object value) { 
 /** * MODEL_KEY_PREFIX="org.springframework.validation.BindingResult." * 以这个开头的属性不需要数据绑定 */
 if (attributeName.startsWith(BindingResult.MODEL_KEY_PREFIX)) { 
 return false;
 }
 
 //用户通过@SessionAttributes注解指定的属性需要进行数据绑定
 if (this.sessionAttributesHandler.isHandlerSessionAttribute(attributeName, value.getClass())) { 
 return true;
 }
 
 //非集合，非数组，非Map，非简单类型的属性都需要进行数据绑定
 return (!value.getClass().isArray() && !(value instanceof Collection) &&
 !(value instanceof Map) && !BeanUtils.isSimpleValueType(value.getClass()));
 }

> 下面是三种过滤条件，表明需要进行数据绑定的属性
> 
>  *  以`org.springframework.validation.BindingResult.`开头的属性不需要数据绑定
>  *  用户通过`@SessionAttributes`注解指定的属性需要进行数据绑定
>  *  非`集合`，非`数组`，非`Map`，非`简单类型`的属性都需要进行数据绑定

# 15 `ModelAndViewContainer`模型视图容器 #

我们先来看一下它的属性

public class ModelAndViewContainer { 
 
 //忽略重定向时的默认模型
 private boolean ignoreDefaultModelOnRedirect = false;
 
 //视图名
 @Nullable
 private Object view;
 
 //默认模型
 private final ModelMap defaultModel = new BindingAwareModelMap();
 
 //重定向模型
 @Nullable
 private ModelMap redirectModel;
 
 private boolean redirectModelScenario = false;
 
 //响应状态码
 @Nullable
 private HttpStatus status;
 
 private final Set<String> noBinding = new HashSet<>(4);
 
 //禁用绑定的属性
 private final Set<String> bindingDisabled = new HashSet<>(4);
 
 //会话状态
 private final SessionStatus sessionStatus = new SimpleSessionStatus();
 
 //请求是否被完全处理
 private boolean requestHandled = false;
 }

## 15.1 数据来源 ##

/** * Return read-only "input" flash attributes from request before redirect. * @param request current request * @return a read-only Map, or {@code null} if not found * @see FlashMap */
 @SuppressWarnings("unchecked")
 @Nullable
 public static Map<String, ?> getInputFlashMap(HttpServletRequest request) { 
 return (Map<String, ?>) request.getAttribute(DispatcherServlet.INPUT_FLASH_MAP_ATTRIBUTE);
 }

/** * Name of request attribute that holds a read-only {@code Map<String,?>} * with "input" flash attributes saved by a previous request, if any. * @see org.springframework.web.servlet.support.RequestContextUtils#getInputFlashMap(HttpServletRequest) */
 //org.springframework.web.servlet.DispatcherServlet.INPUT_FLASH_MAP
 public static final String INPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".INPUT_FLASH_MAP";

> 该方法会得到`request`中所有域属性名为`org.springframework.web.servlet.DispatcherServlet.INPUT_FLASH_MAP`的值

## 15.2 `addAllAttributes(@Nullable Map<String, ?> attributes)`方法，添加数据到视图模型容器中 ##

/** * Copy all attributes to the underlying model. * A shortcut for {@code getModel().addAllAttributes(Map)}. */
 public ModelAndViewContainer addAllAttributes(@Nullable Map<String, ?> attributes) { 
 //由getModel()方法判断将数据添加到defaultModel还是redirectModel中
 getModel().addAllAttributes(attributes);
 return this;
 }
 
 /** * Return the model to use -- either the "default" or the "redirect" model. * The default model is used if {@code redirectModelScenario=false} or * there is no redirect model (i.e. RedirectAttributes was not declared as * a method argument) and {@code ignoreDefaultModelOnRedirect=false}. */
 public ModelMap getModel() { 
 //非重定向
 if (useDefaultModel()) { 
 return this.defaultModel;
 }
 //重定向
 else { 
 if (this.redirectModel == null) { 
 this.redirectModel = new ModelMap();
 }
 return this.redirectModel;
 }
 }
 
 /** * Whether to use the default model or the redirect model. */
 private boolean useDefaultModel() { 
 /** * 只有非重定向场景或 * 重定向模型为null且ignoreDefaultModelOnRedirect属性为false（即忽略重定向） */
 return (!this.redirectModelScenario || (this.redirectModel == null && !this.ignoreDefaultModelOnRedirect));
 }

> 数据会添加到重定向模型或默认模型中

## 15.3 `mergeAttributes(@Nullable Map<String, ?> attributes)`方法，合并模型数据 ##

/** * Copy attributes in the supplied {@code Map} with existing objects of * the same name taking precedence (i.e. not getting replaced). * A shortcut for {@code getModel().mergeAttributes(Map<String, ?>)}. */
 public ModelAndViewContainer mergeAttributes(@Nullable Map<String, ?> attributes) { 
 /** * 由getModel()方法判断将数据添加到defaultModel还是redirectModel中 * mergeAttributes(attributes)方法会合并两个map集合的值 * 注意：同key的直接跳过，不会覆盖 */
 getModel().mergeAttributes(attributes);
 return this;
 }

合并两个`map`集合

/** * Copy all attributes in the supplied {@code Map} into this {@code Map}, * with existing objects of the same name taking precedence (i.e. not getting * replaced). */
 public ModelMap mergeAttributes(@Nullable Map<String, ?> attributes) { 
 if (attributes != null) { 
 attributes.forEach((key, value) -> { 
 if (!containsKey(key)) { 
 put(key, value);
 }
 });
 }
 return this;
 }

## 15.4 `getDefaultModel()`方法，获取默认模型 ##

/** * Return the "default" model created at instantiation. * In general it is recommended to use {@link #getModel()} instead which * returns either the "default" model (template rendering) or the "redirect" * model (redirect URL preparation). Use of this method may be needed for * advanced cases when access to the "default" model is needed regardless, * e.g. to save model attributes specified via {@code @SessionAttributes}. * @return the default model (never {@code null}) * @since 4.1.4 */
 public ModelMap getDefaultModel() { 
 //默认模型
 return this.defaultModel;
 }

## 15.5 `getSessionStatus()`方法，获取会话状态 ##

/** * Return the {@link SessionStatus} instance to use that can be used to * signal that session processing is complete. */
    public SessionStatus getSessionStatus() { 
       return this.sessionStatus;
    }

> 默认的`SessionStatus`的类型为`SimpleSessionStatus`

我们先来看一下`SessionStatus`接口方法

public interface SessionStatus { 
    
        /** * 设置当前会话已完成 */
        void setComplete();
    
        /** * 当前会话是否完成 */
        boolean isComplete();
    
    }

它的简单实现`SimpleSessionStatus`

public class SimpleSessionStatus implements SessionStatus { 
    
        //默认是false，表示会话未完成
        private boolean complete = false;
    
    
        @Override
        public void setComplete() { 
            this.complete = true;
        }
    
        @Override
        public boolean isComplete() { 
            return this.complete;
        }
    }

## 15.6 `getViewName()`方法，获取视图名 ##

/** * Return the view name to be resolved by the DispatcherServlet via a * ViewResolver, or {@code null} if a View object is set. */
    @Nullable
    public String getViewName() { 
       return (this.view instanceof String ? (String) this.view : null);
    }

> 模型视图容器中保存的可能是视图名也可能是视图对象

## 15.7 `isViewReference()`方法，判断是不是视图名 ##

/** * Whether the view is a view reference specified via a name to be * resolved by the DispatcherServlet via a ViewResolver. */
    public boolean isViewReference() { 
       return (this.view instanceof String);
    }

# 16 `ModelAndView` 模型视图 #

> 持有模型和视图，以便控制器可以在单个返回值中同时返回视图和模型

下面是它的属性

public class ModelAndView { 
    
        //视图对象或视图名
        @Nullable
        private Object view;
    
       //模型
        @Nullable
        private ModelMap model;
    
        //响应状态
        @Nullable
        private HttpStatus status;
    
        //是否通过clear()方法清除了该实例
        private boolean cleared = false;
    }

## 16.1 构造方法 ##

/** * Create a new ModelAndView given a view name, model, and HTTP status. * @param viewName name of the View to render, to be resolved * by the DispatcherServlet's ViewResolver * @param model a Map of model names (Strings) to model objects * (Objects). Model entries may not be {@code null}, but the * model Map may be {@code null} if there is no model data. * @param status an HTTP status code to use for the response * (to be set just prior to View rendering) * @since 4.3 */
 public ModelAndView(@Nullable String viewName, @Nullable Map<String, ?> model, @Nullable HttpStatus status) { 
 this.view = viewName;
 if (model != null) { 
 getModelMap().addAllAttributes(model);
 }
 this.status = status;
 }
 
 
 /** * Return the underlying {@code ModelMap} instance (never {@code null}). */
 public ModelMap getModelMap() { 
 if (this.model == null) { 
 this.model = new ModelMap();
 }
 return this.model;
 }

> 根据模型、视图名、响应状态构建一个模型视图对象

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