10.19日记-526互联

public class ExceptionHandlerMethodResolver {
    MethodFilter EXCEPTION_HANDLER_METHODS = method ->
           AnnotatedElementUtils.hasAnnotation(method, ExceptionHandler.class);

   Map<Class<? extends Throwable>, Method> mappedMethods = new HashMap<>(16);

   public ExceptionHandlerMethodResolver(Class<?> handlerType) {
       // 在 @ControllerAdvice 注解的类中获取 @ExceptionHandler 注解的方法
       for (Method method : MethodIntrospector.selectMethods(handlerType, EXCEPTION_HANDLER_METHODS)) {
           // 获取 @ExceptionHandler 其属性value的值，即代表拦截需要处理的异常
           for (Class<? extends Throwable> exceptionType : detectExceptionMappings(method)) {
               // 异常类型 & @ExceptionHandler 注解的方法
               addExceptionMapping(exceptionType, method);
           }
       }
   }

   private void addExceptionMapping(Class<? extends Throwable> exceptionType, Method method) {
       Method oldMethod = this.mappedMethods.put(exceptionType, method);
   }
}