Retrofit vs Feign for Server Side

Both are type-safe HTTP clients for android and Java/Kotlin.

Both makes it easy to consume JSON or XML data by parsing them into POJO.

It is super easy to create Feign Client in Spring Boot application. We just need to add the below dependencies in build.gradle

compile('org.springframework.cloud:spring-cloud-starter-openfeign')
compile('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client')
compile('org.springframework.cloud:spring-cloud-starter-loadbalancer')
compile('org.springframework.cloud:spring-cloud-starter-netflix-hystrix')

@FeignClient("stores")
public interface StoreClient {

    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    List<Store> getStores();
}

Eureka discovery client integration: If your spring boot application is a Eureka client, then spring cloud will make Feign Client eureka aware i.e. Feign will resolve the service in the Eureka service registry. So no need to specify/hardcode host/port/protocol for target service. All you need to have this working is add spring-cloud-starter-netflix-eureka-client dependency in build.gradle and apply the below two annotations to your main class.

@EnableDiscoveryClient
@EnableFeignClients
public class App {

    public static void main(String[] args) {
        SpringApplication.run(ShunyaApp.class, args);
    }
}

Ribbon integration: Spring cloud integrates client side load balancer with feign if spring-cloud-starter-netflix-ribbon is on the classpath. Now Feign enjoys all the benefits of client side load balancing without any extra plumbing. Ribbon will take care of distributing the load on multiple instances of remote service.

Circuit breaker pattern: If Hystrix is on the classpath and feign.hystrix.enabled=true, Feign will wrap all methods with a circuit breaker.

Spring MVC annotations support is added to Feign client by Spring Cloud. So we need not learn any new syntax for using Feign.

The default Spring Web HttpMessageConverters are configured to use with Feign out of the box when used with Spring Cloud.

OpenFeign has pluggable support for both Apache HttpClient and OkHttp as the underlying HttpClient for necessary Http communication. To enable OkHttp in feign, you can set the following property. Similarly you can choose among Jackson and Gson for Json Serialization/DeSerialization, Slf4j for logging.

feign:
  okhttp:
    enabled: true

https://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-feign.html

https://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-ribbon.html

https://github.com/Netflix/feign

https://square.github.io/retrofit/

https://cloud.spring.io/spring-cloud-openfeign/reference/html/