Feign Client Error Handling - Suppress the Error/Exception and convert to 200 success response

Question

I am using feign client to connect to downstream service.

I got a requirement that when one of the downstream service endpoint returns 400 ( it's partial success scenario ) our service need this to be converted to 200 success with the response value.

I am looking for a best way of doing this.

We are using error decoder to handle the errors and the above conversion is applicable for only one endpoint not for all the downstream endpoints and noticed that decode() method should returns exception back.

Answer 1

You will need to create a customized Client to intercept the Response early enough to change the response status and not invoke the ErrorDecoder. The simplest approach is to create a wrapper on an existing client and create a new Response with a 200 status. Here is an example when using Feign's ApacheHttpClient:

public class ClientWrapper extends ApacheHttpClient {
   private ApacheHttpClient delegate;

   public ClientWrapper(ApacheHttpClient client) {
      this.client = client;
   }

   @Override
   public Response execute(Request request, Request.Options options) throws IOException {
      /* execute the request on the delegate */
      Response response = this.client.execute(request, options);

      /* check the response code and change */
      if (response.status() == 400) {
         response = Response.builder(response).status(200).build();
      }
      return response;
   }
}

This customized client can be used on any Feign client you need.