关于WebMvc的配置
1.最暴力的配置方法就是直接继承WebMvcConfigurationSupport
2.比较温柔的做法就是使用注解@EnableWebMvc
这个注解是引入了DelegatingWebMvcConfiguration这样一个代理配置类，它继承了WebMvcConfigurationSupport，
然后通过注入WebMvcConfigurer来进行配置，所以，只要往容器里装入WebMvcConfigurer的自定义类就可以了。
3.自动配置类WebMvcAutoConfiguration里已经引入了WebMvcAutoConfigurationAdapter，也就是WebMvcConfigurer子类，
同样引入了EnableWebMvcConfiguration，是DelegatingWebMvcConfiguration子类，所以连注解@EnableWebMvc也不需要了。
注意：由于自动配置类WebMvcAutoConfiguration的引入条件是@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
所以，使用了上面1或者2时，是不会自动配置的，这样也就失去了自动配置类做的配置。
由此可见，尽量使用第3种方法，优先使用application.properties来配置，不够的地方，添加WebMvcConfigurer子类配置，
只有实在无法满足要求时才使用2甚至1的方法。
实际上Spring的基本调用也比较简单：
1.通过xml或者注解，创建各种HandlerMapping，这些类的目的就是创建从path到Handler的mapping。
HandlerMapping的唯一一个方法就是getHandler
2.便利各个HandlerMapping，找到Handler后，再遍历各个HandlerAdapter，看看有谁能接受这个Handler。
HandlerAdapter的两个主要方法
boolean supports(Object handler);
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
3.有了ModelAndView后，就可以渲染出页面了
①HandlerMapping
BeanNameUrlHandlerMapping
SimpleUrlHandlerMapping//例：/static,/public
RequestMappingHandlerMapping
②HandlerAdapter
Servlet->SimpleServletHandlerAdapter
HttpRequestHandler->HttpRequestHandlerAdapter//例：ResourceHttpRequestHandler
Controller->SimpleControllerHandlerAdapter
HandlerMethod->RequestMappingHandlerAdapter
③HandlerMethodArgumentResolver
// Annotation-based argument resolution
@RequestParam->RequestParamMethodArgumentResolver
RequestParamMapMethodArgumentResolver
@PathVariable->PathVariableMethodArgumentResolver
PathVariableMapMethodArgumentResolver
@MatrixVariable->MatrixVariableMethodArgumentResolver
MatrixVariableMapMethodArgumentResolver
@ModelAttribute->ServletModelAttributeMethodProcessor
@RequestBody->RequestResponseBodyMethodProcessor
@RequestPart->RequestPartMethodArgumentResolver
@RequestHeader->RequestHeaderMethodArgumentResolver
RequestHeaderMapMethodArgumentResolver
@CookieValue->ServletCookieValueMethodArgumentResolver
@Value->ExpressionValueMethodArgumentResolver
@SessionAttribute->SessionAttributeMethodArgumentResolver
@RequestAttribute->RequestAttributeMethodArgumentResolver
// Type-based argument resolution
WebRequest
ServletRequest
MultipartRequest
HttpSession
Principal
Locale
TimeZone
"java.time.ZoneId"
InputStream
Reader
HttpMethod->ServletRequestMethodArgumentResolver
ServletResponse
OutputStream
Writer->ServletResponseMethodArgumentResolver
HttpEntity
RequestEntity->HttpEntityMethodProcessor
RedirectAttributes->RedirectAttributesMethodArgumentResolver
Model->ModelMethodProcessor
Map->MapMethodProcessor
Errors->ErrorsMethodArgumentResolver
SessionStatus->SessionStatusMethodArgumentResolver
UriComponentsBuilder
ServletUriComponentsBuilder->UriComponentsBuilderMethodArgumentResolver
④HandlerMethodReturnValueHandler
ModelAndView->ModelAndViewMethodReturnValueHandler
Model->ModelMethodProcessor
View->ViewMethodReturnValueHandler
StreamingResponseBody
ResponseEntity->StreamingResponseBodyReturnValueHandler
HttpEntity(not RequestEntity)->HttpEntityMethodProcessor
HttpHeaders->HttpHeadersReturnValueHandler
@ModelAttribute->ModelAttributeMethodProcessor
@ResponseBody->RequestResponseBodyMethodProcessor
void || CharSequence->ViewNameMethodReturnValueHandler
Map->MapMethodProcessor
ModelAttributeMethodProcessor