微服务-Feign客户端服务之间传递token

我们使用Spring Cloud 服务间互调，使用Feign声明式服务客户端调用实现。那如何在feign客户端间或feign客户端与server服务端传递token呢？
答案是可以使用Feign拦截器，我使用的版本是Spring Cloud Openfeign 2.0.0.M2，话不多说，上代码

import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;

import javax.servlet.http.HttpServletRequest;

import feign.RequestInterceptor;
import feign.RequestTemplate;

@Configuration // 加上该注解 ，则不需要FeignClient里面加属性configuration
public class FeignHeadersInterceptor implements RequestInterceptor {

  @Override public void apply(RequestTemplate template) {

    HttpServletRequest request = getHttpServletRequest();

    if (Objects.isNull(request)) {
      return;
    }

    Map<String, String> headers = getHeaders(request);
    if (headers.size() > 0) {
      Iterator<Entry<String, String>> iterator = headers.entrySet().iterator();
      while (iterator.hasNext()) {
        Entry<String, String> entry = iterator.next();
        // 把请求过来的header请求头 原样设置到feign请求头中
        // 包括token
        template.header(entry.getKey(), entry.getValue());
      }
    }
  }

  private HttpServletRequest getHttpServletRequest() {
    
    try {
      // 这种方式获取的HttpServletRequest是线程安全的
      return ((ServletRequestAttributes) (RequestContextHolder.currentRequestAttributes())).getRequest();
    } catch (Exception e) {
      
      return null;
    }
  }

  private Map<String, String> getHeaders(HttpServletRequest request) {
    
    Map<String, String> map = new LinkedHashMap<>();
  
    Enumeration<String> enums = request.getHeaderNames();
    while (enums.hasMoreElements()) {
      String key = enums.nextElement();
      String value = request.getHeader(key);
      map.put(key, value);
    }
    
    return map;
  }
}

上述代码中，getHttpServletRequest方法获取Request请求，而getHeaders从Request中拿到请求头信息，最后设置到RequestTemplate的headers中，而RequestTemplate就相当于feign客户端的HttpClient。