Spring MVC之RequestMappingHandlerAdapter初始化

RequestMappingHandlerAdapter基于注解的处理器适配器，目的是用来执行handler，同时返回modelAndView给前端控制器,这块个人感觉是spring mvc的核心了，所以我会详细一些记录。
本篇文章先记录他初始化都做了什么。
先上类图：

通过类图可以看到，实现了InitializingBean接口，所以入口的方法就是 afterPropertiesSet();

下面来看代码：

public void afterPropertiesSet() {
List handlers;
if (this.argumentResolvers == null) { //加载默认的参数解析器
handlers = this.getDefaultArgumentResolvers();
this.argumentResolvers = (new HandlerMethodArgumentResolverComposite()).addResolvers(handlers);
}

if (this.initBinderArgumentResolvers == null) { //加载@initBinder注解的解析器
handlers = this.getDefaultInitBinderArgumentResolvers();
this.initBinderArgumentResolvers = (new HandlerMethodArgumentResolverComposite()).addResolvers(handlers);
}

if (this.returnValueHandlers == null) { //加载默认返回值的解析器
handlers = this.getDefaultReturnValueHandlers();
this.returnValueHandlers = (new HandlerMethodReturnValueHandlerComposite()).addHandlers(handlers);
}

this.initControllerAdviceCache(); //缓存 类有@ControllerAdvice 且@ModelAttribute 和 @InitBinder的注解的方法
}

注意：这些解析器实际上都是一个*****Composite结尾的包装类，实际上就是责任链模式的管理类，提供查找具体的解析器和执行方法，这块内容就不多描述了.

就拿参数解析器为例：

private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() {
List<HandlerMethodArgumentResolver> resolvers = new ArrayList();
resolvers.add(new RequestParamMethodArgumentResolver(this.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)); //没有注解的pojo对象参数 使用它解析的

resolvers.add(new RequestResponseBodyMethodProcessor(this.getMessageConverters()));
resolvers.add(new RequestPartMethodArgumentResolver(this.getMessageConverters()));
resolvers.add(new RequestHeaderMethodArgumentResolver(this.getBeanFactory()));
resolvers.add(new RequestHeaderMapMethodArgumentResolver());
resolvers.add(new ServletCookieValueMethodArgumentResolver(this.getBeanFactory()));
resolvers.add(new ExpressionValueMethodArgumentResolver(this.getBeanFactory()));
resolvers.add(new ServletRequestMethodArgumentResolver());
resolvers.add(new ServletResponseMethodArgumentResolver());
resolvers.add(new HttpEntityMethodProcessor(this.getMessageConverters()));
resolvers.add(new RedirectAttributesMethodArgumentResolver());
resolvers.add(new ModelMethodProcessor());
resolvers.add(new MapMethodProcessor());
resolvers.add(new ErrorsMethodArgumentResolver());
resolvers.add(new SessionStatusMethodArgumentResolver());
resolvers.add(new UriComponentsBuilderMethodArgumentResolver());
if (this.getCustomArgumentResolvers() != null) { //自定义的参数解析器
resolvers.addAll(this.getCustomArgumentResolvers());
}

resolvers.add(new RequestParamMethodArgumentResolver(this.getBeanFactory(), true)); //据说全能的，有时间看下代码
resolvers.add(new ServletModelAttributeMethodProcessor(true));
return resolvers;
}

下面来看initControllerAdviceCache()方法

private void initControllerAdviceCache() {
if (this.getApplicationContext() != null) {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Looking for controller advice: " + this.getApplicationContext());
}
　　　　　　　//获取所有有@ControllerAdvice的Bean
List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(this.getApplicationContext());
Collections.sort(beans, new OrderComparator());
Iterator i$ = beans.iterator();

while(i$.hasNext()) {
ControllerAdviceBean bean = (ControllerAdviceBean)i$.next(); //遍历bean拿到@ModelAttribute的方法
Set<Method> attrMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), MODEL_ATTRIBUTE_METHODS);
if (!attrMethods.isEmpty()) {
this.modelAttributeAdviceCache.put(bean, attrMethods); //缓存起来
this.logger.info("Detected @ModelAttribute methods in " + bean);
}
　　　　　　　　  //拿到有@InitBinder的方法
Set<Method> binderMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), INIT_BINDER_METHODS);
if (!binderMethods.isEmpty()) {
this.initBinderAdviceCache.put(bean, binderMethods); //缓存起来
this.logger.info("Detected @InitBinder methods in " + bean);
}
}

}
}

到此为止，初始化完成