FeignClient configuration in ASP.Net - asp.net

Question

I am trying to create microservices using Spring-boot Java and SteelToe ASP.NET
Step-1: I created a full service using Java (A service with UI and API. It is hosted on PCF). The API has ClassesControler defined inside.
Step-2: Create a microservice using ASP.NET, SteelToe. Register the service in Eureka and make it discoverable using Zuul.
Step-3: Use the Interface, Service approach to access the JAVA microservice(s)
namespace employee-client.Service
{
public interface IRelayService
{
Task<HttpResponseMessage> getClassesList(string relativeUrl = "/api/v1/classes");
}
}
Service with Implementation for Interface:
namespace employee-client.Service
{
public class RelayService : IRelayService
{
DiscoveryHttpClientHandler _handler;
string _accessToken;
private const string BASE_URL = "https://www.example.com";
public QortaService(IDiscoveryClient client, string accessToken)
{
_handler = new DiscoveryHttpClientHandler(client);
_accessToken = accessToken;
}
public async Task<HttpResponseMessage> getClassesList(string relativeUrl)
{
string classesUrl= BASE_URL + relativeUrl;
HttpClient client = GetClient();
HttpRequestMessage request = new HttpRequestMessage();
request.RequestUri = new Uri(classesUrl);
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _accessToken);
return await client.SendAsync(request, HttpCompletionOption.ResponseContentRead);
}
private HttpClient GetClient()
{
var client = new HttpClient(_handler, false);
return client;
}
}
}
I came up with this approach based on the example in SteelToe but I hate hardcoding the BASE_URL.
Question: I very much like the #FeignClient annotation approach used in Java. Any ideas about how I can access an existing microservice in a better way. If so, an example would be much appreciated
Edit:
I modified the question to make more clear.
The flow of traffic is from Java Service to .NET service. .NET service requests for a list of classes from the controller in JAVA service (ClassesController.java)

Answer 1

I'm unclear which direction traffic is flowing in your scenario, but I think you're saying the .NET application is trying to call the Java application. The code you're using is from before HttpClientFactory was introduced and is a bit clunkier than what's possible now in general. Steeltoe can be used with HttpClientFactory for a better overall experience.
Steeltoe has debug logging available to confirm the results of service lookup if you set logging:loglevel:Steeltoe.Common.Discovery = true in your application config.
You didn't mention specifically what isn't working, but I'm guessing you're getting a 404 since it looks like your code will create a request path looking like https://fortuneService/api/fortunes/random/api/v1/classes
If you're looking for something like Feign in .NET, you could try out DHaven.Faux

Answer 2

For others who are looking for the same:
namespace employee-client.Service
{
public class RelayService : IRelayService
{
private const string CLASSES_API_SERVICEID = "classes-api";
IDiscoveryClient _discoveryClient;
DiscoveryHttpClientHandler _handler;
string _accessToken;
public RelayService(IDiscoveryClient discoveryClient, string accessToken)
{
_discoveryClient = discoveryClient;
_handler = new DiscoveryHttpClientHandler(client);
_accessToken = accessToken;
}
public async Task<HttpResponseMessage> getClassesList()
{
var classesApiInstances = _discoveryClient.GetInstances(CLASSES_API_SERVICEID);
Uri classesApiUri = classesApiInstances[0].Uri;
string classesUrl= classesApiUri.AbsoluteUri + relativeUrl;
HttpClient httpClient = GetClient();
HttpRequestMessage request = new HttpRequestMessage();
request.RequestUri = new Uri(classesUrl);
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _accessToken);
return await httpClient.SendAsync(request, HttpCompletionOption.ResponseContentRead);
}
private HttpClient GetClient()
{
var client = new HttpClient(_handler, false);
return client;
}
}
}