拦截器

拦截器分同步拦截器和异步拦截器；

HandlerInterceptor

方法和执行时机

可以看DispathcerServlet的原来确定它的三个方法的执行时机；

AsynHandlerInterceptor

看注释，主要用来清理在并发环境加清理ThreadLocal的数据；

ResponseBodyAdvice

对返回值备注了@ResponseBody或者返回ResponseEntity做了一些加工；

会在使用消息转换器转换为json数据之前进行数据转换输出；

package com.springbootpractice.interceptor.config;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.springbootpractice.interceptor.config.interceptor.MyInterceptor;
import lombok.SneakyThrows;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.MethodParameter;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import java.util.HashMap;
import java.util.Map;

/**
 * 说明：配置拦截器和设置统一返回格式
 * @author carter
 * 创建时间： 2020年02月19日 11:03 下午
 **/
@Configuration
@ControllerAdvice
public class WebConfig implements WebMvcConfigurer, ResponseBodyAdvice {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        HandlerInterceptor myIntercepter = new MyInterceptor() ;
        registry.addInterceptor(myIntercepter).addPathPatterns("/**");
    }

    @Override
    public boolean supports(MethodParameter returnType, Class converterType) {
        return true;
    }

    @SneakyThrows
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {

       Map<String,Object> map = new HashMap();
       map.put("result","true");
       map.put("data",body);
       return new ObjectMapper().writeValueAsString(map);
    }
}