io.scalecube.examples.helloworld.Example2 Maven / Gradle / Ivy

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package io.scalecube.examples.helloworld;

import io.scalecube.examples.helloworld.service.GreetingServiceImpl;
import io.scalecube.examples.helloworld.service.api.Greeting;
import io.scalecube.services.Microservices;
import io.scalecube.services.ServiceCall.Call;
import io.scalecube.services.api.ServiceMessage;

import org.reactivestreams.Publisher;

import reactor.core.publisher.Mono;

/**
 * The Hello World project is a time-honored tradition in computer programming. It is a simple exercise that gets you
 * started when learning something new. Let’s get started with ScaleCube!
 * 
 * the example starts 2 cluster member nodes. 1. seed is a member node and holds no services of its own. 2. The
 * microservices variable is a member that joins seed member and provision GreetingService
 * instance. This Code demonstrates executing a ScaleCube service using a ServiceMessage rather than an
 * explicit Service interface thus eliminating Service interface dependency.
 */
public class Example2 {
  public static void main(String[] args) {
    // ScaleCube Node node with no members
    Microservices seed = Microservices.builder().startAwait();

    // Construct a ScaleCube node which joins the cluster hosting the Greeting Service
    Microservices microservices = Microservices.builder()
        .seeds(seed.cluster().address())
        .services(new GreetingServiceImpl())
        .startAwait();

    // Create a proxy to the seed service node
    Call service = seed.call();
    final String SERVICE_QUALIFIER = "/io.scalecube.Greetings/sayHello";

    // Create a ServiceMessage request with service qualifier and data
    ServiceMessage request = ServiceMessage.builder()
        .qualifier(SERVICE_QUALIFIER)
        .data("joe")
        .build();
    // Execute the Greeting Service to emit a single Greeting response
    Publisher publisher = service.create().requestOne(request, Greeting.class);

    // Convert the Publisher using the Mono API which ensures it will emit 0 or 1 item.
    Mono.from(publisher).subscribe(consumer -> {
      // handle service response
      Greeting greeting = consumer.data();
      System.out.println(greeting.message());
    });

    // shut down the nodes
    seed.shutdown().block();
    microservices.shutdown().block();

  }

}