Spring - how to pass automatically http header between microservices

Question

I'm having multiple microservices

1. MangerApp 
2. ProcessApp
3. DoingStuffApp
4. .....

the "MangerApp Microservices" get an Http-Request I'm looking for a way to transfer automatically some of the HTTP headers in the call, while I don't want to go over each place and do - add Headers, my HTTP headers are stored as a thread-local Map.

since I call to other microservices, with RestTemplate I have many different calls some get/post/put/etc... changing each one them and passing the header manually is not that efficient. I'm looking for a way to manage it, other than extending the RestTemplate Class now.

Answer 1

You can use a ClientHttpRequestInterceptor to achieve what you need.

1) Create a HeaderInterceptor implementing ClientHttpRequestInterceptor. In this example it gets the Authorization and Accept headers from a ThreadLocal and propagates them:

public class HeaderInterceptor implements ClientHttpRequestInterceptor{

    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {

                    HttpHeaders headers = request.getHeaders();
        List<String> authorization = HeaderThreadLocal.getAuthorization()
        List<String> accept = HeaderThreadLocal.getAuthorization();

        headers.addAll("Authorization", authorization);
        headers.addAll("Accept", accept);
        return execution.execute(request, body);
    }
}

2) Configure your RestTemplate bean adding the header interceptor:

restTemplate.getInterceptors().add(new HeaderInterceptor());