@FeignClient 微服务传递head

使用微服务的架构开发的项目，需要时常调用其他服务的接口，@FeignClient默认的设置会导致请求头
head丢失，重写请求拦截器，将head头信息放入到新请求当中

@Configuration
public class FeignClientsConfig implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate requestTemplate) {
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        if (attributes == null) {
            return;
        }
        HttpServletRequest request = attributes.getRequest();
        Enumeration<String> headerNames = request.getHeaderNames();
        if (headerNames != null) {
            while (headerNames.hasMoreElements()) {
                String name = headerNames.nextElement();
                 //新请求会导致长度改变，过滤
                if ("content-length".equalsIgnoreCase(name)) {
                    continue;
                }
                //防止传递格式修改，过滤
                if ("accept-encoding".equalsIgnoreCase(name)) {
                    continue;
                }
                String value = request.getHeader(name);
                requestTemplate.header(name, value);
            }
        }
    }
}