gRPC & High Performance APIs · Lección

Servicio gRPC unario sencillo

Implemente desde cero un servicio y un cliente gRPC básicos de «solicitud-respuesta» utilizando el código generado.

Servicio gRPC unario sencillo es una lección gratuita de gRPC & High Performance APIs en CoddyKit. Esta es la lección 3 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de gRPC & High Performance APIs, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de gRPC & High Performance APIs incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

Unary RPC: Simple Interactions

In gRPC, a Unary RPC is the simplest communication pattern. It's like a traditional function call where a client sends a single request to the server, and the server responds with a single reply.

Think of it as a standard "request-response" model. The client waits for the server's response before proceeding.

Client sends one message.
Server sends one message back.
This is the most common RPC type.

Reviewing Our Protobuf

Before we dive into implementation, let's briefly recall our simple Protocol Buffer (Protobuf) definition. This schema defines the service and messages we'll use.

We'll implement the Greeter service with a SayHello method.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "com.example.grpc.helloworld";
option java_outer_classname = "HelloWorldProto";

package helloworld;

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

(Remember, code generation was covered in a previous lesson.)

Server: Extending the Base

After generating code from our .proto file, gRPC creates an abstract base class for our server. For our Greeter service, it's GreeterGrpc.GreeterImplBase.

To implement our service, we create a new class that extends this base class and overrides the service method(s).

class GreeterImpl extends GreeterGrpc.GreeterImplBase {
    @Override
    public void sayHello(HelloRequest req,
                         StreamObserver<HelloReply> resObserver) {
        // ... implementation goes here ...
    }
}

The StreamObserver is how we send the response back.

Server Logic: Building Response

Inside the sayHello method, we receive the HelloRequest. We can then process it and build our HelloReply.

The StreamObserver.onNext() method sends the reply, and onCompleted() signals that the RPC is finished.

class GreeterImpl extends GreeterGrpc.GreeterImplBase {
    @Override
    public void sayHello(HelloRequest req,
                         StreamObserver<HelloReply> resObserver) {
        System.out.println("Received name: " + req.getName());
        HelloReply reply = HelloReply.newBuilder()
                                   .setMessage("Hello " + req.getName())
                                   .build();
        resObserver.onNext(reply);     // Send the response
        resObserver.onCompleted();  // Mark RPC as complete
    }
}

Full Server Implementation

Now, let's put it all together to create and start a gRPC server. This server will listen for incoming client requests on a specific port.

Try running this code and then proceed to the client implementation!

package com.example.grpc.helloworld;

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

public class HelloWorldServer {
    private Server server;

    private void start() throws IOException {
        int port = 50051;
        server = ServerBuilder.forPort(port)
                .addService(new GreeterImpl())
                .build()
                .start();
        System.out.println("Server started, listening on " + port);
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                System.err.println("*** shutting down gRPC server since JVM is shutting down");
                try {
                    HelloWorldServer.this.stop();
                } catch (InterruptedException e) {
                    e.printStackTrace(System.err);
                }
                System.err.println("*** server shut down");
            }
        });
    }

    private void stop() throws InterruptedException {
        if (server != null) {
            server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
        }
    }

    private void blockUntilShutdown() throws InterruptedException {
        if (server != null) {
            server.awaitTermination();
        }
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        final HelloWorldServer server = new HelloWorldServer();
        server.start();
        server.blockUntilShutdown();
    }

    static class GreeterImpl extends GreeterGrpc.GreeterImplBase {
        @Override
        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
            System.out.println("Received: " + req.getName());
            HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}

Client Stub: Connecting & Calling

On the client side, gRPC also generates "stubs." These stubs provide the methods to call the remote service, making it feel like a local method call.

For unary RPCs, we often use a blocking stub, which means the client waits for the server's response.

// Blocking stub for our Greeter service
GreeterGrpc.GreeterBlockingStub blockingStub;

The stub will handle all the underlying network communication details for you!

Client Channel: The Connection

Before using a stub, the client needs a channel. A channel represents a connection to a gRPC server at a specific host and port.

Channels are typically long-lived and can be reused for multiple RPC calls.

ManagedChannel channel = ManagedChannelBuilder.forAddress("localhost", 50051)
                                            .usePlaintext() // No TLS for simplicity
                                            .build();
blockingStub = GreeterGrpc.newBlockingStub(channel);

usePlaintext() is okay for local dev but avoid in production!

Full Client Implementation

With the channel and stub ready, we can now make our unary RPC call. We'll build a HelloRequest and send it via the stub.

Run the server from the previous step, then run this client to see it in action!

package com.example.grpc.helloworld;

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;

import java.util.concurrent.TimeUnit;

public class HelloWorldClient {
    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;

    public HelloWorldClient(String host, int port) {
        channel = ManagedChannelBuilder.forAddress(host, port)
                .usePlaintext() // For simplicity, no TLS
                .build();
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }

    public void shutdown() throws InterruptedException {
        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
    }

    public void greet(String name) {
        System.out.println("Will try to greet " + name + "...");
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response;
        try {
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e) {
            System.err.println("RPC failed: " + e.getStatus());
            return;
        }
        System.out.println("Greeting: " + response.getMessage());
    }

    public static void main(String[] args) throws Exception {
        HelloWorldClient client = new HelloWorldClient("localhost", 50051);
        try {
            String user = "CoddyKit User";
            if (args.length > 0) {
                user = args[0];
            }
            client.greet(user);
        } finally {
            client.shutdown();
        }
    }
}

Unary Flow: Request & Reply

When you run the client, it sends the HelloRequest to the server. The server receives it, processes it using our GreeterImpl, and sends back a HelloReply.

Client: Creates channel, stub, builds HelloRequest.
Client: Calls blockingStub.sayHello(request).
Server: Receives HelloRequest in sayHello method.
Server: Processes, builds HelloReply, calls onNext() and onCompleted().
Client: Receives HelloReply, continues execution.

This completes one full unary RPC cycle!

Unary Service Check

Consider a gRPC unary service. Which component is responsible for receiving a request, processing it, and sending back a single response?

Recap: Simple Unary RPC

Great job! You've learned how to implement a basic unary gRPC service and client:

We reviewed the Protobuf schema for our service.
We implemented the server logic by extending the generated base class and handling requests.
We built a gRPC server instance and started it.
On the client side, we used a channel to connect and a blocking stub to make the RPC call.

Unary RPCs are fundamental to gRPC, providing a robust way for simple request-response communication. Next, we'll explore more advanced streaming patterns!

Preguntas frecuentes

¿La lección «Servicio gRPC unario sencillo» es gratis?

Sí — el texto completo de «Servicio gRPC unario sencillo» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de gRPC & High Performance APIs, actualiza a CoddyKit PRO. El curso de gRPC & High Performance APIs incluye 4 lecciones en total.

¿Qué aprenderé en «Servicio gRPC unario sencillo»?

Implemente desde cero un servicio y un cliente gRPC básicos de «solicitud-respuesta» utilizando el código generado. Practicas gRPC & High Performance APIs con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar gRPC & High Performance APIs?

No se requiere experiencia previa. gRPC & High Performance APIs en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 3 de 4.

¿Cuánto tiempo toma la lección «Servicio gRPC unario sencillo»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de gRPC & High Performance APIs?

Sí. Cada lección de gRPC & High Performance APIs incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

Todas las lecciones de este curso

Definición de esquemas Protobuf
Generación de código gRPC
Servicio gRPC unario sencillo
RPC de streaming: del servidor, del cliente y bidireccional

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