gRPC-Java HelloWorld使用筆記 原

環境：Windows，JDK8，Maven3，Eclipse

在Eclipse創建Maven Project，項目名稱“grpcdemo”

編寫pom.xml，直接將gRPC-Java裏examples裏的pom文件內容複製過來，主要是以下部分：

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <grpc.version>1.15.0</grpc.version><!-- CURRENT_GRPC_VERSION -->
    <protobuf.version>3.5.1</protobuf.version>
    <protoc.version>3.5.1-1</protoc.version>
    <netty.tcnative.version>2.0.7.Final</netty.tcnative.version>
    <!-- required for jdk9 -->
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-netty-shaded</artifactId>
      <version>${grpc.version}</version>
    </dependency>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-protobuf</artifactId>
      <version>${grpc.version}</version>
    </dependency>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-stub</artifactId>
      <version>${grpc.version}</version>
    </dependency>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-alts</artifactId>
      <version>${grpc.version}</version>
    </dependency>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-testing</artifactId>
      <version>${grpc.version}</version>
      <scope>test</scope>
    </dependency>

    <!-- Used in HelloWorldServerTls -->
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-netty</artifactId>
      <version>${grpc.version}</version>
    </dependency>
    <dependency>
      <groupId>io.netty</groupId>
      <artifactId>netty-tcnative-boringssl-static</artifactId>
      <version>${netty.tcnative.version}</version>
    </dependency>

    <dependency>
      <groupId>com.google.api.grpc</groupId>
      <artifactId>proto-google-common-protos</artifactId>
      <version>1.0.0</version>
    </dependency>
    <dependency>
      <groupId>com.google.protobuf</groupId>
      <artifactId>protobuf-java-util</artifactId>
      <version>${protobuf.version}</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-core</artifactId>
      <version>1.9.5</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <extensions>
      <extension>
        <groupId>kr.motd.maven</groupId>
        <artifactId>os-maven-plugin</artifactId>
        <version>1.5.0.Final</version>
      </extension>
    </extensions>
    <plugins>
      <plugin>
        <groupId>org.xolstice.maven.plugins</groupId>
        <artifactId>protobuf-maven-plugin</artifactId>
        <version>0.5.1</version>
        <configuration>
          <protocArtifact>com.google.protobuf:protoc:${protoc.version}:exe:${os.detected.classifier}</protocArtifact>
          <pluginId>grpc-java</pluginId>
          <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}</pluginArtifact>
        </configuration>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>compile-custom</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>1.4.1</version>
        <executions>
          <execution>
            <id>enforce</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <requireUpperBoundDeps/>
              </rules>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

新建src/main/proto文件夾，編寫hello.proto文件（相關protobuf語法可自行搜索）

// Copyright 2015 The gRPC Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

在命令窗口切換到項目根目錄，運行

mvn compile

運行完成後，項目結構如下

編寫服務端代碼

/**
 * Server that manages startup/shutdown of a {@code Greeter} server.
 */
public class HelloWorldServer {
  private static final Logger logger = Logger.getLogger(HelloWorldServer.class.getName());

  private Server server;

  private void start() throws IOException {
    /* The port on which the server should run */
    int port = 50051;
    server = ServerBuilder.forPort(port)
        .addService(new GreeterImpl())
        .build()
        .start();
    logger.info("Server started, listening on " + port);
    Runtime.getRuntime().addShutdownHook(new Thread() {
      @Override
      public void run() {
        // Use stderr here since the logger may have been reset by its JVM shutdown hook.
        System.err.println("*** shutting down gRPC server since JVM is shutting down");
        HelloWorldServer.this.stop();
        System.err.println("*** server shut down");
      }
    });
  }

  private void stop() {
    if (server != null) {
      server.shutdown();
    }
  }

  /**
   * Await termination on the main thread since the grpc library uses daemon threads.
   */
  private void blockUntilShutdown() throws InterruptedException {
    if (server != null) {
      server.awaitTermination();
    }
  }

  /**
   * Main launches the server from the command line.
   */
  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) {
      HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
      responseObserver.onNext(reply);
      responseObserver.onCompleted();
    }

    @Override
    public void sayHelloAgain(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
      HelloReply reply = HelloReply.newBuilder().setMessage("Hello again " + req.getName()).build();
      responseObserver.onNext(reply);
      responseObserver.onCompleted();
    }
  }
}

編寫客戶端代碼

public class HelloWorldClient {
  private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());

  private final ManagedChannel channel;
  private final GreeterGrpc.GreeterBlockingStub blockingStub;

  /** Construct client connecting to HelloWorld server at {@code host:port}. */
  public HelloWorldClient(String host, int port) {
    this(ManagedChannelBuilder.forAddress(host, port)
        // Channels are secure by default (via SSL/TLS). For the example we disable TLS to avoid
        // needing certificates.
        .usePlaintext()
        .build());
  }

  /** Construct client for accessing HelloWorld server using the existing channel. */
  HelloWorldClient(ManagedChannel channel) {
    this.channel = channel;
    blockingStub = GreeterGrpc.newBlockingStub(channel);
  }

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

  /** Say hello to server. */
  public void greet(String name) {
    logger.info("Will try to greet " + name + " ...");
    HelloRequest request = HelloRequest.newBuilder().setName(name).build();
    HelloReply response;
    try {
      response = blockingStub.sayHello(request);
    } catch (StatusRuntimeException e) {
      logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
      return;
    }
    logger.info("Greeting: " + response.getMessage());
    try {
      response = blockingStub.sayHelloAgain(request);
    } catch (StatusRuntimeException e) {
      logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
      return;
    }
    logger.info("Greeting: " + response.getMessage());
  }

  /**
   * Greet server. If provided, the first element of {@code args} is the name to use in the
   * greeting.
   */
  public static void main(String[] args) throws Exception {
    HelloWorldClient client = new HelloWorldClient("localhost", 50051);
    try {
      /* Access a service running on the local machine on port 50051 */
      String user = "world";
      if (args.length > 0) {
        user = args[0]; /* Use the arg as the name to greet if provided */
      }
      client.greet(user);
    } finally {
      client.shutdown();
    }
  }
}