透传从网关传递来的 http header 的方法

HeaderInterceptor.java

package com.gkeeps.clients;

import feign.RequestInterceptor;
import feign.RequestTemplate;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;

@EnableDiscoveryClient
@EnableFeignClients
@EnableCircuitBreaker
@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public RequestInterceptor headerInterceptor() {
        return new RequestInterceptor() {
            @Override
            public void apply(RequestTemplate requestTemplate) {
                ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder
                        .getRequestAttributes();
                if(attributes == null){
                    // 将“隔离模式”调整为“信号量”，才可以透传
                    // hystrix.command.default.execution.isolation.strategy=SEMAPHORE
                    return;
                }
                HttpServletRequest request = attributes.getRequest();
                Enumeration<String> headerNames = request.getHeaderNames();
                // 可以增加参数，透传指定 http header
                if (headerNames != null) {
                    while (headerNames.hasMoreElements()) {
                        String name = headerNames.nextElement();
                        String values = request.getHeader(name);
                        requestTemplate.header(name, values);
                    }
                }
            }
        };
    }
}