【拦截器】HandlerInterceptor接口

 package org.springframework.web.servlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import org.springframework.web.servlet.ModelAndView;

 public interface HandlerInterceptor {

     boolean preHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3) throws Exception;

     void postHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3, ModelAndView var4) throws Exception;

     void afterCompletion(HttpServletRequest var1, HttpServletResponse var2, Object var3, Exception var4) throws Exception;

 }

HandlerInterceptor 拦截器有三个方法：preHandle、postHandle、afterCompletion。

1，preHandle:处理器的预处理，返回true表示流程继续，或者返回结果或者移交给下一个拦截器；返回false表示不会继续处理(流程中断)，而是直接response。不会继续调用postHandle和afterCompletion方法。
2，postHandle：后处理回调方法，发生在视图渲染之前。参数ModelAndView可以为空，不为空时会对数据进行处理或者视图渲染。
3，afterCompletion：整个请求处理完毕回调方法，即在视图渲染完毕时回调。

拦截器是链式，可以同时存在。执行顺序为mvc声明的顺序one by one执行。

拦截器的原理是反射机制，

import com.security.jwt.StatelessAuthenticationInterceptor;

import com.fasterxml.jackson.annotation.JsonInclude;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.google.common.collect.Lists;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.autoconfigure.web.HttpMessageConverters;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.http.MediaType;

import org.springframework.http.converter.HttpMessageConverter;

import org.springframework.http.converter.StringHttpMessageConverter;

import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;

import org.springframework.web.servlet.config.annotation.CorsRegistry;

import org.springframework.web.servlet.config.annotation.InterceptorRegistry;

import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration

public class WebConfig extends WebMvcConfigurerAdapter {

    @Autowired

    private StatelessAuthenticationInterceptor statelessAuthenticationInterceptor;

    @Override

    public void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(statelessAuthenticationInterceptor);

    }

}