HandlerMethodArgumentResolver的原理是什么？

Question

如题：在一个controller的请求方法中，有两个自定义的参数注解@UserInfo和@SchoolInfo @RequestMapping(value = "/filter/test2") public String test2(@RequestBody String o, @UserInfo UserInfoVo userInfoVo, @SchoolInfo SchoolInfoVo schoolInfoVo) { System.out.println("Controller中获取的请求数据：" + o); System.out.println("自定义注解UserInfo的值：" + userInfoVo); System.out.println("自定义注解SchoolInfo的值：" + schoolInfoVo); return "OK"; } 实现两个参数解析器如下： public class LoginUserInfoMethodArgumentResolver implements HandlerMethodArgumentResolver { @Override public boolean supportsParameter(MethodParameter parameter) { // return parameter.getParameterType().equals(UserInfoVo.class); System.out.println("login" + parameter.hasParameterAnnotation(UserInfo.class)); return parameter.hasParameterAnnotation(UserInfo.class); } @Override public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { HttpServletRequest httpServletRequest = webRequest.getNativeRequest(HttpServletRequest.class); String str = HttpHelper.getBodyString(httpServletRequest); System.out.println("参数解析器login获取的请求数据：" + str); UserInfoVo u = new UserInfoVo(); u.setName("洪桓"); u.setAge(233); return u; } } public class SchoolInfoMethodArgumentResolver implements HandlerMethodArgumentResolver { @Override public boolean supportsParameter(MethodParameter parameter) { System.out.println("school" + parameter.hasParameterAnnotation(SchoolInfo.class)); return parameter.hasParameterAnnotation(SchoolInfo.class); } @Override public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { HttpServletRequest httpServletRequest = webRequest.getNativeRequest(HttpServletRequest.class); String str = HttpHelper.getBodyString(httpServletRequest); System.out.println("参数解析器school获取的请求数据：" + str); SchoolInfoVo schoolInfoVo = new SchoolInfoVo(); schoolInfoVo.setName("HNU"); schoolInfoVo.setYear(1980); return schoolInfoVo; } } WebMvcConfigurerAdapter中实现顺序如下： @Override public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) { super.addArgumentResolvers(argumentResolvers); argumentResolvers.add(new LoginUserInfoMethodArgumentResolver()); argumentResolvers.add(new SchoolInfoMethodArgumentResolver()); } 最后输出结果 logintrue loginfalse schooltrue 如果按照list的添加顺序算的话，第一遍扫描判断parameter.hasParameterAnnotation(UserInfo.class)是true，第二遍扫描parameter.hasParameterAnnotation(UserInfo.class)和parameter.hasParameterAnnotation(SchoolInfo.class)分别是flase和true，为什么第二次参数解析器中会返回false

Answer 1

第一次是传 @UserInfo UserInfoVo userInfoVo 进去，所以是true

第二次是传 @SchoolInfo SchoolInfoVo schoolInfoVo 进去，所以是false，然后遍历到 SchoolInfoMethodArgumentResolver 返回true了