java在过滤器中为http请求加请求头header

前言

        现在有一个需求场景：每一个请求我都需要在请求头里面加上token这个请求头，作为一种校验机制，传统的接口可以通过设置一个全局的变量，然后通过页面携带过来（大概就是先将我们的token放在session中，写一个服务用来获取session中的token，然后主页面用 ajax 调用接口，将 token放在隐藏域中，然后将请求头放进来，用 ajax 方法，这里不想细说了），但是有一个情况是通过页面传递的并不一定都会适用所有接口，比如上传和下载的接口有时候请求头里面就没有token 参数，可能是上传和下载是用表单提交的。
这个时候如何将请求头通过后台的方法加进来？
想到用过滤器，用后台方法强制加入请求头。

我这里加的是将用户唯一标识加在请求头上，并在自己需要的时候自己获取

1.创建拦截器，核心代码为 addHeader方法，将userid添加到请求头中

package com.kaying.luck.interceptor;

import com.kaying.luck.dao.draw.user.UserDao;
import com.kaying.luck.exception.ServiceException;
import com.kaying.luck.pojo.draw.user.dos.UserDO;
import com.kaying.luck.response.enums.ApiResponseCodeEnum;
import com.kaying.luck.utils.applicationContext.MyApplicationContext;
import org.apache.commons.lang3.StringUtils;
import org.apache.tomcat.util.http.MimeHeaders;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

/**
 * @author csp
 * @create 2021-11-23 14:54
 * @description
 */
@Component
public class BaseInterceptor implements HandlerInterceptor {

    @Autowired
    private UserDao userDao = MyApplicationContext.getBean(UserDao.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object o) throws Exception {

        String userId = request.getHeader("userId");
        if (StringUtils.isBlank(userId)){
            throw new ServiceException(ApiResponseCodeEnum.ERROR_USER_ID, "未查询到用户信息");
        }
        UserDO userDO = userDao.getUserByUserId(userId);
        if (userDO == null) {
            userDO = new UserDO();
            userDO.setId(null);
            userDO.setUserId(userId);
            userDO.setUserOrderStatus(0);
            userDao.insert(userDO);
        }
        Map<String,String> map=new HashMap<>();
        map.put("userId",userId);
        addHeader(request,map);
        return true;
    }

    private void addHeader(HttpServletRequest request, Map<String, String> headerMap) {
        if (headerMap==null||headerMap.isEmpty()){
            return;
        }

        Class<? extends HttpServletRequest> c=request.getClass();
        //System.out.println(c.getName());
        System.out.println("request实现类="+c.getName());
        try{
            Field requestField=c.getDeclaredField("request");
            requestField.setAccessible(true);

            Object o=requestField.get(request);
            Field coyoteRequest=o.getClass().getDeclaredField("coyoteRequest");
            coyoteRequest.setAccessible(true);

            Object o2=coyoteRequest.get(o);
            System.out.println("coyoteRequest实现类="+o2.getClass().getName());
            Field headers=o2.getClass().getDeclaredField("headers");
            headers.setAccessible(true);

            MimeHeaders mimeHeaders=(MimeHeaders) headers.get(o2);
            for (Map.Entry<String,String> entry:headerMap.entrySet()){
                mimeHeaders.removeHeader(entry.getKey());
                mimeHeaders.addValue(entry.getKey()).setString(entry.getValue());
            }

        }catch (Exception e){
            e.printStackTrace();
        }

    }


    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse response, Object o, ModelAndView modelAndView) throws Exception {
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "*");
        response.setHeader("Access-Control-Allow-Credentials", "true");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    }

}

2.配置拦截器，拦截器需要配置才能使用

package com.kaying.luck.config.interceptor;

import com.kaying.luck.interceptor.BaseInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * 拦截器需要配置才可以使用，也可以在这里注入其他的类
 *
 * @author yt
 * @create 2022/10/17 14:26
 */
@Configuration
public class BaseInterceptorConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 添加拦截器
        registry.addInterceptor(new BaseInterceptor())
                //添加拦截路径
                .addPathPatterns("/**")
                //排除的拦截路径（此路径不拦截）
                .excludePathPatterns("/swagger/**","/error","/download/**","/wx/**","/address/**","/management/**","/callback/**",
                        "/favicon.ico","/swagger2/**", "/swagger*", "/swagger*/**", "/webjars/**", "/doc.html", "/swagger-ui.html", "/swagger-resources/**", "/v2/api-docs**");

    }

    /**
     * 开启跨域
     */
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        // 设置允许跨域的路由
        registry.addMapping("/**")
                // 设置允许跨域请求的域名
                .allowedOriginPatterns("*")
                // 是否允许证书（cookies）
                .allowCredentials(true)
                // 设置允许的方法
                .allowedMethods("*")
                // 跨域允许时间
                .maxAge(3600);
    }


}

4.在要拦截的方法接收参数上添加 @RequestHeader注解

 @ApiOperation(value = "根据用户UserId查询用户信息")
    @GetMapping("get/user")
    public ApiResponse<UserDO> getUserByUserId( @RequestHeader("userId") String userId) {
        System.out.println("userId = " + userId);
        if (StringUtils.isBlank(userId)) {
            throw new ServiceException(ApiResponseCodeEnum.FAIL, "获取用户信息失败");
        }
        UserDO userDO = userLoginService.getUserByUserId(userId);
        return ApiResponse.success(userDO);
    }

5.测试访问是可以拿到userid的