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I'm not a Java developer but I'm trying to put together a quick start snippet to help Java users consume our service using code generated from .proto service definitions.

I've cobbled together some code, drawing from the examples in grpc/grpc-java, but I don't feel comfortable with how the host and port parameters are being set, or with the null return from the createUser method.

I'd appreciate any feedback on how easy the code below would be to implement, and highlight any significant issues or improvements that could be made to improve performance and developer productivity.

Example User Client class:

package com.example.UserClient;

import io.grpc.ManagedChannel;
import io.grpc.StatusRuntimeException;
import io.grpc.testing.TestUtils;
import io.grpc.netty.GrpcSslContexts;
import io.grpc.netty.NegotiationType;
import io.grpc.netty.NettyChannelBuilder;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;

import javax.net.ssl.SSLException;
import java.io.File;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.example.UserGrpc;
import com.example.UserGrpc.UserBlockingStub;
import com.example.UserOuterClass.NewUser;
import com.example.UserOuterClass.NewUserResponse;

public class UserClient 

 private static final Logger logger = Logger.getLogger(UserClient.class.getName());

 private static String host;
 private static int port;

 private final ManagedChannel channel;
 private final UserBlockingStub userStub;

 private static SslContext buildSslContext(String h, int p, String trustFile, String clientCertFile, String clientKeyFile) throws SSLException 
 mHost = host;
 mPort = port;
 return GrpcSslContexts.forClient()
 .trustManager(new File(trustFile))
 .keyManager(new File(clientCertFile), new File(clientKeyFile))
 .build();
 

 public QuickStart(String host, int port, String trustFile, String clientCertFile, String clientKeyFile) throws SSLException 
 this(buildSslContext(host, port, trustFile, clientCertFile, clientKeyFile));
 

 public QuickStart(SslContext sslContext) throws SSLException 
 this(NettyChannelBuilder.forAddress(host, port)
 .negotiationType(NegotiationType.TLS)
 .sslContext(sslContext)
 .build());
 

 QuickStart(ManagedChannel channel) 
 this.channel = channel;
 userStub = UserGrpc.newBlockingStub(channel);
 

 public NewUserResponse createUser(NewUser user) 
 NewUserResponse newUser;
 try 
 newUser = userStub.createUser(user);
 return newUser;
 catch (StatusRuntimeException e) 
 logger.log(Level.WARNING, "RPC failed: 0", e.getStatus());
 return null;
 
 

 // Other method implementations....

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

Consuming the class:

UserClient client;
try 
 client = new UserClient("api.example.com", 443, "ca.pem", "client.pem", "client-key.pem");
 NewUser user = NewUser.newBuilder()
 .setUsername("TestyMcTest")
 .setEmailAddress("Testy.McTest@testy.com")
 // additional params...
 .build();

 NewUserResponse response = client.createUser(user);

 catch(Exception e) 
 e.printStackTrace();