FeignClient is passing on headers

Question

I have about 10 microservices all built with Spring boot 2 using Eureka and FeignClients. My microservices use certain header values to keep track of data so when a FeignClient is used it needs to pass on certain values that are in the incoming request. So if Microservice 1 does a call to Microservice 2 it must pass on the headers from the incoming request onto microservice 2. I haven't been able to find out how I can do that. I understand their is @Header however if you have 20 FeignClients then you don't want to have to manually add the @header to all the FeignClients. Can you indicate that FeignClients must read a certain header from the incoming request and pass it on in the FeignClient?

Answer 1

You can use request interceptor in Feign.

Example Implementation:

Request Interceptor:

@Component
public class MyRequestInterceptor implements RequestInterceptor {

    @Override
    public void apply(RequestTemplate template) {
        ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        String authorization = requestAttributes.getRequest().getHeader(HttpHeaders.AUTHORIZATION);
        if(null != authorization) {
            template.header(HttpHeaders.AUTHORIZATION, authorization);
        }
    }

}

Bean Configuration:

@Configuration
public class CustomFeignConfig {

    @Bean
    public Contract feignContract() {
        return new feign.Contract.Default();
    }

    @Bean
    public MyRequestInterceptor basicAuthRequestInterceptor() {
        return new MyRequestInterceptor();
    }

    @Bean
    public OkHttpClient client() {
        return new OkHttpClient();
    }

}