Running a service

In this step, we'll do three things with the code we obtained from our proto file; we'll create a server instance, add an empty gRPC service, and then lastly test connecting to the server.

What you need

You need to have the generated Java code obtained from the previous step. You can always download the full version, instead of creating one yourself.

1. Declare an empty service

Create a file BlogService.java and declare an empty blog service. We'll implement the service methods later on in this file. For now, leave it empty.

BlogService.java
package example.armeria.blog.grpc;

final class BlogService extends BlogServiceGrpc.BlogServiceImplBase {}

2. Add a service to a server

Build a service and server using Armeria's ServerBuilder to serve our service.

  1. Create a main class for our server. You can see the full version of the file here.

    Main.java
    package example.armeria.blog.grpc;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public final class Main {
  private static final Logger logger = LoggerFactory.getLogger(Main.class);
}

  2. Create a service instance using Armeria's GrpcService.builder().

    Main.java
    import com.linecorp.armeria.server.grpc.GrpcService;
import com.linecorp.armeria.server.Server;

public final class Main {
...
  static Server newServer(int port) throws Exception {
    final GrpcService grpcService =
      GrpcService.builder()
                 .addService(new BlogService())
                 .build();
  }
}

  3. Build and return a new server instance using Armeria's ServerBuilder.

    Main.java
    public final class Main {
  static Server newServer(int port) throws Exception {
    ...
    return Server.builder()
                 .http(port)
                 .service(grpcService)
                 .build();

  }

3. Run the server and service

Create a server instance and run the blog service.

  1. Create a server instance in the main() method.

    Main.java
    public static void main(String[] args) throws Exception {
    final Server server = newServer(8080);

    server.closeOnJvmShutdown().thenRun(() -> {
        logger.info("Server has been stopped.");
    });

    server.start().join();
}

  2. Start the server by running the Main.main() method on your IDE or using Gradle.

    ./gradlew run

    Your server is running if you see the following message.

    [armeria-boss-http-*:8080] INFO com.linecorp.armeria.server.Server - Serving HTTP at /[0:0:0:0:0:0:0:0%0]:8080 - http://127.0.0.1:8080/

4. Test connecting to the server

Let's create test code and connect to the server by sending a request using a client stub. Note that we'll use test code to verify what we implement along the way.

  1. Create a file, BlogServiceTest.java, under {project_root}/src/test/java/example/armeria/blog/grpc as follows. You can see the full version of the file here.

    BlogServiceTest.java
    package example.armeria.blog.grpc;
import example.armeria.blog.grpc.BlogServiceGrpc.BlogServiceBlockingStub;

class BlogServiceTest {
  static BlogServiceBlockingStub client;
}

  2. In the BlogServiceTest class, add a test method as follows. Although we haven't implemented any service methods, we'll call one just to check whether we can connect to the server.

    BlogServiceTest.java
    import org.junit.jupiter.api.Test;
import com.linecorp.armeria.client.grpc.GrpcClients;

@Test
void connect() {
  client = GrpcClients.newClient("http://127.0.0.1:8080/",
                                 BlogServiceBlockingStub.class);
  client.createBlogPost(CreateBlogPostRequest.newBuilder().build());
}

  3. Make sure that your server is running. If you have not stopped the server, it should already be running. Otherwise, restart the server by running the Main.main() method.

  4. Run the test case on your IDE or using Gradle.

    ./gradlew test

    Your client sent a request to the service successfully if the test fails and throws an "UNIMPLEMENTED" exception.

    UNIMPLEMENTED: Method example.armeria.blog.grpc.BlogService/CreateBlogPost is unimplemented

    This is because we are yet to implement the service method to create a blog post. One thing we did check is that our service does return something to a client call.

What's next

In this step, we've created and added an empty gRPC service to a server. We've also written a test and made a call to the server.

Next, we'll get on with implementing a service method for creating blog posts.

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