Implementing Unary API Server

A unary API server in gRPC handles a single request and sends a single response. Here’s a detailed guide on how to implement one:

1. Define the Service and Messages

• Create a .proto file to define the service and message definitions.
• Use clear and concise names for services and messages.
• Specify the request and response types for the unary API.

Example:

Protocol Buffers

syntax = "proto3";

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

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

2. Generate Server Code  

• Use the protoc compiler to generate server code from the .proto file.
• The generated code will include an interface that defines the service and a base class for implementing the service.

Example:

Java

public interface GreeterGrpc {
  public static abstract class GreeterImplBase extends io.grpc.stub.AbstractStub<GreeterImplBase> {
    ...
  }
}

3. Implement the Service

• Create a class that extends the generated base class.
• Override the method corresponding to the unary API you defined.
• Implement the logic for handling the request and generating the response.

Example:

Java

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

4. Start the Server

• Create a ManagedChannelBuilder object to configure the server.
• Set the server address and port.
• Build the channel and start the server.

Example:

Java

public class Server {
    public static void main(String[] args) throws IOException, InterruptedException {
        ServerBuilder serverBuilder = ServerBuilder.forPort(50051);   
        serverBuilder.addService(new GreeterImpl());
        Server server = serverBuilder.build();

        server.start();
        System.out.println("Server started on port " + server.getPort());

        server.awaitTermination();
    }
}

By following these steps, you can create a basic unary API server in gRPC. You can customize the server implementation to handle specific use cases and add additional features as needed.