handlerMethodArgumentResolver：方法参数解析器接口，这个接口是springmvc参数解析绑定的核心接口。不同的参数类型绑定都是通过实行这个接口来实现。也可以通过实现这个接口来自定义参数解析器。这个接口有如下两个方法：

public interface HandlerMethodArgumentResolver{   //该解析器是否支持parameter参数的解析            boolean supportsParameter (MethodParameter parameter);                //将方法参数从给定请求(webRequest)解析为参数值并返回   Object resolveArgument(MethodParameter parameter,                    ModelAndViewContainer mavContainer,                    NativeWebRequest webRequest,                   WebDataBinderFactory binderFactory) throws Exceptions;}

 

初始化

RequestMappingHandlerAdapter.java类的afterProperitesSet方法初始化相关方法参数解析器，代码如下：

public void afterPropertiesSet(){    if(this.argumentResolvers==null){       //初始化springmvc默认的方法参数解析器，并添加到argumentResolvers(HandlerMethodArgumentResolverComposite)      List
     
       resolvers = getDefaultArgumentResolvers():      this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);               }     if(this.initBinderArgumentResolvers==null){         //初始化springmvc默认的初始化绑定器(@InitBinder)参数解析器，并添加至initBinderArgumentResolvers(HandlerMethosArgumentResolverComposite)        List
      
        resolvers = getDefaultInitBinderArgumentResolvers();        this.initBinderArgumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);       }     if(this.returnValueHandlers==null){         //获取默认的方法返回值解析器       List
       
         handler = getDefaultReturnValueHandlers();       this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);    }     initControllerAdviceCache();}
       
      
     

 

现在我们进入getDefaultArgumentResolvers方法，代码如下

//默认的参数解析，创建了默认的24个参数解析器，并添加至resolvers//这里的24个参数解析器都是针对不同的参数类型来解析的private List
     
       getDefaultArgumentResolvers() {    List
      
        resolvers = new ArrayList
       
        ();    // 基于注解的参数解析器    //一般用于带有@RequestParam注解的简单参数绑定，简单参数比如byte、int、long、double、String以及对应的包装类型    resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));    //用于处理带有@RequestParam注解，且参数类型为Map的解析绑定    resolvers.add(new RequestParamMapMethodArgumentResolver());    //一般用于处理带有@PathVariable注解的默认参数绑定    resolvers.add(new PathVariableMethodArgumentResolver());    //也是用于带有@PathVariable注解的Map相关参数绑定，后续还有一些默认的参数解析器。后续还有一些参数解析器，我这里都不一一解释了。想具体确认某个参数会交个哪个参数解析器处理，可以通过以下解析器的supportsParameter(MethodParameter parameter)方法得知    resolvers.add(new PathVariableMapMethodArgumentResolver());    resolvers.add(new MatrixVariableMethodArgumentResolver());    resolvers.add(new MatrixVariableMapMethodArgumentResolver());    resolvers.add(new ServletModelAttributeMethodProcessor(false));    resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters()));    resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters()));    resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));    resolvers.add(new RequestHeaderMapMethodArgumentResolver());    resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory()));    resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));    // 基于类型的参数解析器    resolvers.add(new ServletRequestMethodArgumentResolver());    resolvers.add(new ServletResponseMethodArgumentResolver());    resolvers.add(new HttpEntityMethodProcessor(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());    // Custom arguments    if (getCustomArgumentResolvers() != null) {        resolvers.addAll(getCustomArgumentResolvers());    }
       
      
     

 

参数解析器添加至HandlerMethodArgumentResolverComposite这个类，它是实现了HandlerMethodArgumentResolver接口。这里运用设计模式的中的composite模式（组合模式），在springmvc中，所有请求的参数解析都是进入HandlerMethodArgumentResolverComposite类来实现的。它有两个成员变量，如下

 

//它的元素在RequestMappingHandlerAdapter类的afterPropertiesSet方法中被添加，存放的是springmvc默认的一些HandlerMethodArgumentResolver参数解析器private final List
     
       argumentResolvers = new LinkedList
      
       Resolver();//存放已经解析过的参数，已经对应的HandlerMethodAgrumentResolver解析器，加快查找过程private final Map
       
         argumentResolverCache = new ConcurrentHashMap
        
         (256);
        
       
      
     

 

 

 

 

 

 

 

 

 

 

参考资料：https://www.cnblogs.com/w-y-c-m/p/8443892.html