问题描述

想在postHandle方法里执行addHeader方法来补充一些Header信息（如分页信息），但是最后执行却未如期显示

拦截器源码

import com.zhangziwa.practisesvr.utils.response.ResponseContext;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

@Component
public class ResponsePostInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

		# 想在postHandle方法里执行addHeader方法来补充一些Header信息
        HttpHeaders headers = ResponseContext.getHeaders();
        if (headers != null) {
            headers.forEach((key, values) -> values.forEach((value) -> {
                if (!response.getHeaderNames().contains(key)) {
                    response.addHeader(key, value);
                }
            }));
        }

        if (ResponseContext.getResponseCode() != null) {
            response.setStatus(ResponseContext.getResponseCode().value());
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        ResponseContext.clear();
    }
}

Controller 构造初始的HttpHeaders

    @RequestMapping(value = "/getAllStudents4", method = RequestMethod.GET)
    public ResponseEntity<List<Student>> getAllStudents4() {
        System.err.println("***Controller.getAllStudents4***");

        List<Student> students = userService.listStudents3(1, 5);
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.add("test", "test");
        return ResponseEntity.ok().headers(httpHeaders).contentType(MediaType.APPLICATION_JSON).body(students);
    }

postHandle 补充HttpHeaders的代码正常执行

执行结果却没有补充的HttpHeaders

原因分析

[Ref] springboot设置返回的response中的header解决办法

解决方案

方案1：postHandle追加HttpHeaders的逻辑前移到preHandle方法

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.err.println("***ResponsePostInterceptor.preHandle***");
        response.addHeader("test1", "test1");
        return true;
    }

验证可行

弊端

preHandle执行时机是在进入Controller层之前，如果要追加的HttpHeaders是在Controller层里计算得到的，则此方案完全用不上

方案2：使用ResponseBodyAdvice + @ControllerAdvice

Further Reading ： @ControllerAdvice

源码：HandlerInterceptor 去除补充HttpHeaders逻辑

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

@Component
public class ResponsePostInterceptor implements HandlerInterceptor {

    //在Controller执行之前调用，如果返回false，controller不执行
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.err.println("***ResponsePostInterceptor.preHandle***");
        return true;
    }

    //controller执行之后，且页面渲染之前调用
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.err.println("***ResponsePostInterceptor.postHandle***");
        if (response.isCommitted()) {
            System.out.println("response is committed");
            return;
        }
    }

    //页面渲染之后调用，一般用于资源清理操作
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.err.println("***ResponsePostInterceptor.afterCompletion***");
        ResponseContext.clear();
    }
}

源码：ResponseBodyAdvice 补充HttpHeaders逻辑

import org.springframework.core.MethodParameter;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import static java.util.Objects.nonNull;

@ControllerAdvice
public class ResponsePostAdvice implements ResponseBodyAdvice {


    @Override
    public boolean supports(MethodParameter returnType, Class converterType) {
        System.err.println("***ResponsePostAdvice.supports***");
        return true;
    }

    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class clazz, ServerHttpRequest request, ServerHttpResponse response) {
        System.err.println("***ResponsePostAdvice.beforeBodyWrite***");
        HttpHeaders headers = response.getHeaders();

        // 分页信息添加到ServerHttpResponse
        HttpHeaders headersContext = ResponseContext.getHeaders();

        // 实现方式1: 一次性梭哈 重复项新值覆盖旧值
//        if (nonNull(headersContext) && !headersContext.isEmpty()) {
//            headers.addAll(headersContext);
//        }

        // 实现方式1: 逐个补充 重复项不添加
        if (nonNull(headersContext) && !headersContext.isEmpty()) {
            headersContext.forEach((key, values) -> values.forEach((value) -> {
                headers.addIfAbsent(key, value);
            }));
        }


        // 状态码添加到ServerHttpResponse
        if (nonNull(ResponseContext.getResponseCode())) {
            response.setStatusCode(ResponseContext.getResponseCode());
        }
        return body;
    }
}

验证好用

补充：执行顺序为 ResponseBodyAdvice → HandlerInterceptor

***ResponsePostInterceptor.preHandle***
***Controller.getAllStudents4***
***ResponsePostAdvice.supports***
***ResponsePostAdvice.beforeBodyWrite***
***ResponsePostInterceptor.postHandle***
***ResponsePostInterceptor.afterCompletion***