本文實現Java和Python之間通過grpc互動，只使用最基本的單項rpc。

一、Java實現grpc

使用idea新建maven專案，專案目錄如下

專案的pom.xml檔案如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>test</groupId>
    <artifactId>grpc</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty-shaded</artifactId>
            <version>1.15.0</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>1.15.0</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>1.15.0</version>
        </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:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.15.0:exe:${os.detected.classifier}</pluginArtifact>
                    <protoSourceRoot>src/main/resources/proto</protoSourceRoot>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>

        </plugins>
    </build>
</project>
 

其中proto檔案如下：

helloworld.proto

syntax = "proto3";
package example;
option java_package = "com.zhj.grpc";
option java_outer_classname = "HelloWorldServiceProto";
option java_multiple_files = true;

// The greeting service definition.
service Greeter {
    // Sends a greeting
    rpc SayHello (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;
}
 

其中package一定要和後面Python中的package設定的值一樣，，，要不。。。很難受找不出錯

然後在專案的根目錄下編譯：

mvn compile

這時會生成相應的Java檔案：

然後編寫服務端程式碼：

package com.helloworld;
//import com
import com.zhj.grpc.GreeterGrpc;
import com.zhj.grpc.HelloReply;
import com.zhj.grpc.HelloRequest;
import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;

import java.io.IOException;
import java.util.logging.Logger;

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 Server server;

    private void start() throws IOException {
        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 {
        /** 原子Integer */
    //    public AtomicInteger count = new AtomicInteger(0);

        @Override
        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
//            System.out.println("call sayHello");
            HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
//            System.out.println(count.incrementAndGet() + Thread.currentThread().getName());
        }
    }
}
 

客戶端程式碼：

package com.helloworld;


import com.zhj.grpc.GreeterGrpc;
import com.zhj.grpc.HelloReply;
import com.zhj.grpc.HelloRequest;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;
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 ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;

    /**
     * Construct client connecting to HelloWorld server at {@code host:port}.
     */
    public HelloWorldClient(String host, int port) {

        channel = ManagedChannelBuilder.forAddress(host, port)
                .usePlaintext(true)
                .build();
        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());
    }

    /**
     * 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 {

            String user = "world";
            if (args.length > 0) {
                user = args[0];
            }
            client.greet(user);
        } finally {
            client.shutdown();
        }
    }
}

然後先執行服務端，再執行客戶端，客戶端會收到如下資訊：

九月 13, 2018 6:18:43 下午 com.helloworld.HelloWorldClient greet
資訊: Will try to greet world ...
九月 13, 2018 6:18:43 下午 com.helloworld.HelloWorldClient greet
資訊: Greeting: Hello world

Process finished with exit code 0

二、Python實現grpc

grpc安裝：pip install grpcio

grpcbuf相關庫：pip install grpcbuf

編譯工具：pip install grpcio-tools

Python專案目錄如下：

proto檔案（與Java使用的proto檔案相同）：

syntax = "proto3";
package example;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (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example目錄下編譯：

python -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. ./helloworld.proto 

會生成helloworld_pb2_grpc.py和helloworld_pb2.py檔案，下面在client和sever中呼叫這兩個檔案。

服務端：

greeter_server.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-

import time

import grpc
from concurrent import futures
from example import helloworld_pb2, helloworld_pb2_grpc

_ONE_DAY_IN_SECONDS = 60 * 60 * 24


class Greeter(helloworld_pb2_grpc.GreeterServicer):

    def SayHello(self, request, context):
        return helloworld_pb2.HelloReply(message='Hello, %s!' % request.name)


def serve():
    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
    helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
    server.add_insecure_port('[::]:50051')
    server.start()
    try:
        while True:
            time.sleep(_ONE_DAY_IN_SECONDS)
    except KeyboardInterrupt:
        server.stop(0)


if __name__ == '__main__':
    serve()

客戶端：

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#from __future__ import print_function
import grpc
from example import helloworld_pb2, helloworld_pb2_grpc

def run():
    # NOTE(gRPC Python Team): .close() is possible on a channel and should be
    # used in circumstances in which the with statement does not fit the needs
    # of the code.
    with grpc.insecure_channel('localhost:50051') as channel:
        stub = helloworld_pb2_grpc.GreeterStub(channel)
        response = stub.SayHello(helloworld_pb2.HelloRequest(name='you'))
    print("Greeter client received: " + response.message)


if __name__ == '__main__':
    run()

先執行服務端，再執行客戶端，客戶端顯示：

/home/zhj/.virtualenvs/test4-TkH3JH9C/bin/python /home/zhj/project/grpc/python/client/greeter_client.py
Greeter client received: Hello, you!

Process finished with exit code 0

三、Java和Pythongrpc都已實現，現在可以實現兩種語言之間通訊：

java-server + python-client 或者 python-server + java-client，都會顯示一樣的東西。

再次提示一下，Java和Python使用的proto檔案一定要相同，尤其是package這一項也要相同！！