DemoApplication.java

package demo;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.Output;
import org.springframework.cloud.stream.messaging.Source;
import org.springframework.context.annotation.Bean;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.hateoas.Resources;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.Collection;
import java.util.Collections;
import java.util.stream.Collectors;

@EnableBinding(Source.class)
@EnableZuulProxy
@EnableCircuitBreaker
@EnableDiscoveryClient
@SpringBootApplication
public class DemoApplication {

    @Bean
    AlwaysSampler alwaysSampler() {
        return new AlwaysSampler();
    }

    @Bean
    CommandLineRunner runner(DiscoveryClient dc) {
        return args ->
                dc.getInstances("reservation-service")
                        .forEach(si -> System.out.println(String.format(
                                "%s %s:%s", si.getServiceId(), si.getHost(), si.getPort())));
    }

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

@RestController
@RequestMapping("/reservations")
class ReservationApiGatewayRestController {

    @Autowired
    @LoadBalanced
    private RestTemplate rt;

    @Autowired
    @Output(Source.OUTPUT)
    private MessageChannel out;


    public Collection<String> getReservationNamesFallback() {
        return Collections.emptyList();
    }


    @RequestMapping(method = RequestMethod.POST)
    public void accept(@RequestBody Reservation reservation) {
        Message<String> build =
                MessageBuilder.withPayload(reservation.getReservationName()).build();
        this.out.send(build);
    }

    @RequestMapping("/names")
    @HystrixCommand(fallbackMethod = "getReservationNamesFallback")
    public Collection<String> getReservationNames() {

        ParameterizedTypeReference<Resources<Reservation>> parameterizedTypeReference =
                new ParameterizedTypeReference<Resources<Reservation>>() {
                };

        ResponseEntity<Resources<Reservation>> exchange = rt.exchange(
                "http://reservation-service/reservations", HttpMethod.GET, null, parameterizedTypeReference);

        return exchange
                .getBody()
                .getContent()
                .stream()
                .map(Reservation::getReservationName)
                .collect(Collectors.toList());
    }

}

class Reservation {

    private Long id;
    private String reservationName;

    public Long getId() {
        return id;
    }

    public String getReservationName() {
        return reservationName;
    }
}