Reactive Streams Wrapper

This module wraps Feign's http requests in a Reactive Streams Publisher, enabling the use of Reactive Stream Publisher return types. Supported Reactive Streams implementations are:

• Reactor (Mono and Flux)
• ReactiveX (RxJava) (Flowable only)

To use these wrappers, add the feign-reactive-wrappers module, and your desired reactive-streams implementation to your classpath. Then configure Feign to use the reactive streams wrappers.

public interface GitHubReactor {
      
  @RequestLine("GET /repos/{owner}/{repo}/contributors")
  Flux<Contributor> contributorsFlux(@Param("owner") String owner, @Param("repo") String repo);
      
  @RequestLine("GET /repos/{owner}/{repo}/contributors")
  Mono<List<Contributor>> contributorsMono(@Param("owner") String owner, @Param("repo") String repo);
  
  class Contributor {
      String login;

      public String getLogin() {
          return login;
      }

      public void setLogin(String login) {
          this.login = login;
      }
  }
}

public class ExampleReactor {
  public static void main(String args[]) {
    GitHubReactor gitHub = ReactorFeign.builder() 
      .decoder(new ReactorDecoder(new JacksonDecoder()))     
      .target(GitHubReactor.class, "https://api.github.com");
    
    List<GitHubReactor.Contributor> contributorsFromFlux = gitHub.contributorsFlux("OpenFeign", "feign")
      .collectList()
      .block();
    List<GitHubReactor.Contributor> contributorsFromMono = gitHub.contributorsMono("OpenFeign", "feign")
      .block();
  }
}

public interface GitHubReactiveX {
      
  @RequestLine("GET /repos/{owner}/{repo}/contributors")
  Flowable<Contributor> contributors(@Param("owner") String owner, @Param("repo") String repo);
  
  class Contributor {
    String login;
    
    public Contributor(String login) {
      this.login = login;
    }
  }
}

public class ExampleRxJava2 {
  public static void main(String args[]) {
    GitHubReactiveX gitHub = RxJavaFeign.builder() 
      .decoder(new RxJavaDecoder(new JacksonDecoder()))     
      .target(GitHub.class, "https://api.github.com");
    
    List<Contributor> contributors = gitHub.contributors("OpenFeign", "feign")
      .collect(Collectors.toList())
      .block();
  }
}

Considerations

These wrappers are not reactive all the way down, given that Feign generated requests are synchronous. Requests still block, but execution is controlled by the Publisher and their related Scheduler. While this may not be ideal in terms of a fully reactive application, providing these wrappers provide an intermediate upgrade path for Feign.

Streaming

Methods that return java.util.streams Types are not supported. Responses are read fully, the wrapped in the appropriate reactive wrappers.

Iterable and Collections responses

Due to the Synchronous nature of Feign requests, methods that return Iterable types must specify the collection in the Publisher. For Reactor types, this limits the use of Flux as a response type.