gRPC简介

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gRPC简介。

向POM中添加下面的依赖：

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<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-all</artifactId>
  <version>0.7.2</version>
</dependency>

添加maven-protoc-plugin，Maven插件官网

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<pluginRepositories>
  <pluginRepository>
    <releases>
      <updatePolicy>never</updatePolicy>
    </releases>
    <snapshots>
      <enabled>false</enabled>
    </snapshots>
    <id>central</id>
    <name>Central Repository</name>
    <url>https://repo.maven.apache.org/maven2</url>
  </pluginRepository>
  <pluginRepository>
    <id>protoc-plugin</id>
    <url>https://dl.bintray.com/sergei-ivanov/maven/</url>
  </pluginRepository>
</pluginRepositories>
<build>
  <extensions>
    <extension>
      <groupId>kr.motd.maven</groupId>
      <artifactId>os-maven-plugin</artifactId>
      <version>1.2.3.Final</version>
    </extension>
  </extensions>
  <plugins>
    <plugin>
      <groupId>com.google.protobuf.tools</groupId>
      <artifactId>maven-protoc-plugin</artifactId>
      <version>0.4.2</version>
      <configuration>
        <protocArtifact>com.google.protobuf:protoc:3.0.0-alpha-3.1:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:0.7.1:exe:${os.detected.classifier}</pluginArtifact>
      </configuration>
      <executions>
        <execution>
          <goals>
            <goal>compile</goal>
            <goal>compile-custom</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Maven的版本不能太低，需要 >= 3.2

proto文件默认需要放在src/main/proto目录下,protobuf 默认会在这个目录下搜索proto文件。

如果想修改输出位置，可以添加

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<outputDirectory>
    ${basedir}/src/main/java
</outputDirectory>

hello_world.proto:

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syntax = "proto3";

package helloworld;

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

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

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

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

gRPC推荐使用proto3

然后进行mvn protoc:compile 和 mvn protoc:compile-custom进行编译就会生成对应的Java类。

然后进行编写客户端代码和服务器端代码。

HelloWorldClient.java

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package io.grpc.examples.helloworld;

import io.grpc.ChannelImpl;
import io.grpc.transport.netty.NegotiationType;
import io.grpc.transport.netty.NettyChannelBuilder;

import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A simple client that requests a greeting from the {@link HelloWorldServer}.
 */
public class HelloWorldClient {
  private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());

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

  /** Construct client connecting to HelloWorld server at {@code host:port}. */
  public HelloWorldClient(String host, int port) {
    channel =
        NettyChannelBuilder.forAddress(host, port).negotiationType(NegotiationType.PLAINTEXT)
            .build();
    blockingStub = GreeterGrpc.newBlockingStub(channel);
  }

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

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

  /**
   * 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();
    }
  }
}

HelloWorldService.java

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package io.grpc.examples.helloworld;

import io.grpc.ServerImpl;
import io.grpc.stub.StreamObserver;
import io.grpc.transport.netty.NettyServerBuilder;

import java.util.logging.Logger;

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

  /* The port on which the server should run */
  private int port = 50051;
  private ServerImpl server;

  private void start() throws Exception {
    server = NettyServerBuilder.forPort(port)
        .addService(GreeterGrpc.bindService(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();
    }
  }

  /**
   * Main launches the server from the command line.
   */
  public static void main(String[] args) throws Exception {
    final HelloWorldServer server = new HelloWorldServer();
    server.start();
  }

  private class GreeterImpl implements GreeterGrpc.Greeter {

    @Override
    public void sayHello(HelloRequest req, StreamObserver<HelloResponse> responseObserver) {
      HelloResponse reply = HelloResponse.newBuilder().setMessage("Hello " + req.getName()).build();
      responseObserver.onValue(reply);
      responseObserver.onCompleted();
    }
  }
}

最后进行mvn compile。