The feeling of Feign is very like JPA with CrudRepository: you defined the entity and CrudRepository generate all the CRUD methods for you, all you need just create interface to implement that.

Feign is very similar that way: on Consumer side, you define the interface and annotate to wire it with the producer service, then you can use that interface as local call.

Open Feign Client Setup

1. Dependency:

	implementation 'org.springframework.cloud:spring-cloud-starter-openfeign'

1. Annotation on Spring boot Application class:

@SpringBootApplication
@EnableFeignClients
public class HelloWorldConsumerApplication {

	@Bean
    @LoadBalanced
	public RestTemplate restTemplate(){
		return new RestTemplate();
	}

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

1. Define interface and use @FeignClient annotation to wire it to producer

            //this is the target serivce application name
   @FeignClient("producer-helloworld-service")
   public interface HelloWorldClient {
                //this is the path of target service	
    @GetMapping("/test/greeting")
    String getGreeting();
   }
   

2. Implements

In your client application, use as following, first you wire the interface and then call the method from the interface:

    private final HelloWorldClient helloWorldClient;

    public HelloWorldServiceConsumer(RestTemplate restTemplate, HelloWorldClient helloWorldClient){
        super();
        this.helloWorldClient = helloWorldClient;
    }

    @GetMapping("/withFeign")
    public String testHelloWorldServiceFeign(){
        String answer = this.helloWorldClient.getGreeting();
        return getAnswer(answer);
    }

    private String getAnswer(String answer){
        if("Hello World".equals(answer)){
            return "Successful called producer-helloworld-service";
        }else{
            return "Failed to call producer-helloworld-service";
        }
    }

Conclusion

• Feign client is easier than restTemplate.
• You also can specify the url and ipaddress for those service that not register with Eureka server.