Java 开发 gRPC 服务和客户端

2022-10-30 19:33:09

新建一个普通的Maven项目：

配置pom文件，导入gRPC的依赖和插件

pom 中增加外部依赖

注意，下面的增加 maven 插件： protobuf-maven-plugin: protobuf 的插件，不是 gRPC的插件，产生的代码只会是 protobuf 序列化、反序列化的代码，没有gRPC通讯部分的代码。

增加 maven 插件： protobuf-maven-plugin: 配置

<build>

  <extensions>

    <extension>

      <groupId>kr.motd.maven</groupId>

      <artifactId>os-maven-plugin</artifactId>

      <version>1.4.1.Final</version>

    </extension>

  </extensions>

  <plugins>

    <plugin>

      <groupId>org.xolstice.maven.plugins</groupId>

      <artifactId>protobuf-maven-plugin</artifactId>

      <version>0.5.0</version>

      <configuration>

        <!--

          The version of protoc must match protobuf-java. If you don't depend on

          protobuf-java directly, you will be transitively depending on the

          protobuf-java version that grpc depends on.

        -->

        <protocArtifact>com.google.protobuf:protoc:3.0.0-beta-2:exe:${os.detected.classifier}</protocArtifact>

        <pluginId>grpc-java</pluginId>

        <pluginArtifact>io.grpc:protoc-gen-grpc-java:0.13.2:exe:${os.detected.classifier}</pluginArtifact>

      </configuration>

      <executions>

        <execution>

          <goals>

            <goal>compile</goal>

            <goal>compile-custom</goal>

          </goals>

        </execution>

      </executions>

    </plugin>

  </plugins>

</build>

完整的 pom 文件如下：

<?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">

<groupId>com.ghj1976</groupId>

<artifactId>myGRPCDemo2</artifactId>

<version>1.0-SNAPSHOT</version>

</dependency>

</dependencies>

<build>

<groupId>kr.motd.maven</groupId>

<artifactId>os-maven-plugin</artifactId>

<version>1.4.1.Final</version>

</extension>

</extensions>

<groupId>org.xolstice.maven.plugins</groupId>

<artifactId>protobuf-maven-plugin</artifactId>

<!--

The version of protoc must match protobuf-java. If you don't depend on

protobuf-java directly, you will be transitively depending on the

protobuf-java version that grpc depends on.

-->

<protocArtifact>com.google.protobuf:protoc:3.0.0-beta-2:exe:${os.detected.classifier}</protocArtifact>

<pluginArtifact>io.grpc:protoc-gen-grpc-java:0.13.2:exe:${os.detected.classifier}</pluginArtifact>

</configuration>

<goals>

<goal>compile</goal>

<goal>compile-custom</goal>

</goals>

</execution>

</executions>

</plugin>

</plugins>

</build>

</project>

编写 proto 文件，并编译产生对应的 java文件

简单期间这里直接用的 helloworld.proto 文件，内容如下：

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// * Neither the name of Google Inc. nor the names of its

// contributors may be used to endorse or promote products derived from

// this software without specific prior written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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) {}

}

// The request message containing the user's name.

message HelloRequest {

string name = 1;

}

// The response message containing the greetings

message HelloReply {

string message = 1;

}

生成 protobuf 序列化和反序列化代码

注意，这里我们使用的maven 插件是 protobuf的插件，只能产生protobuf的序列化和反序列化的代码，不能产生gRPC通讯的代码。

如果我们只需要产生这部分代码是，才需要使用这个插件。

这个插件的用法参考下图：

如果用命令行生成，则命令是：

$ protoc --java_out=./java/ ./proto/helloworld.proto

生成 gRPC 通讯部分代码

这时候我们应该使用的是 protoc-gen-grpc-java插件。

这个插件的获取和编译方法请参考： http://www.cnblogs.com/ghj1976/p/5454881.html

我们这时候产生对应java代码的命令如下：

$ protoc --plugin=protoc-gen-grpc-java=/Users/ghj1976/project/github/grpc/grpc-java/compiler/build/exe/java_plugin/protoc-gen-grpc-java --grpc-java_out=./java/ ./proto/helloworld.proto

这两部生成的文件如下：

GreeterGrpc.java 是 protoc-gen-grpc-java 插件生成的，其他文件时 protoc 生成的。

编写服务器端代码

我们服务器端的代码如下，生成的文件在io.grpc.examples.helloworld，我们的服务器端代码在 com.ghj1976 ：

package com.ghj1976;

import io.grpc.Server;

import io.grpc.ServerBuilder;

import io.grpc.examples.helloworld.GreeterGrpc;

import io.grpc.examples.helloworld.HelloReply;

import io.grpc.examples.helloworld.HelloRequest;

import io.grpc.stub.StreamObserver;

import java.io.IOException;

import java.util.logging.Logger;

/**

* Created by ghj1976 on 16/5/4.

public class HelloWorldServer {

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

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(){

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();

}

// block 一直到退出程序

private void blockUntilShutdown() throws InterruptedException {

if (server != null){

server.awaitTermination();

}

public static void main(String[] args) throws IOException, InterruptedException {

final HelloWorldServer server = new HelloWorldServer();

server.start();

server.blockUntilShutdown();

}

// 实现定义一个实现服务接口的类

private class GreeterImpl extends GreeterGrpc.AbstractGreeter {

@Override

public void sayHello(HelloRequest req,StreamObserver<HelloReply> responseObserver){

HelloReply reply = HelloReply.newBuilder().setMessage(("Hello "+req.getName())).build();

responseObserver.onNext(reply);

responseObserver.onCompleted();

}

运行这个类的 main 方法，就可以在 50051 端口启动服务。

go实现的服务器端代码在:

https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_server/main.go

编写客户端代码

为了实现跨语言的调用，我们可以用下面 go 实现的客户端来试验。

https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_client/main.go

如果用 Java 写客户端的话，则是下面代码：

package com.ghj1976;

import io.grpc.ManagedChannel;

import io.grpc.ManagedChannelBuilder;

import io.grpc.StatusRuntimeException;

import io.grpc.examples.helloworld.GreeterGrpc;

import io.grpc.examples.helloworld.HelloReply;

import io.grpc.examples.helloworld.HelloRequest;

import java.util.concurrent.TimeUnit;

import java.util.logging.Level;

import java.util.logging.Logger;

/**

* Created by ghj1976 on 16/5/4.

public class HelloWorldClient {

private final ManagedChannel channel;

private final GreeterGrpc.GreeterBlockingStub blockingStub;

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

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);

}

public void greet(String 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());

}

public static void main(String[] args) throws InterruptedException {

HelloWorldClient client = new HelloWorldClient("127.0.0.1",50051);

try{

String user = "world";

if (args.length > 0){

user = args[0];

}

client.greet(user);

}finally {

client.shutdown();

}

码农公寓

新建一个普通的Maven项目：

配置pom文件，导入gRPC的依赖和插件

编写 proto 文件，并编译产生对应的 java文件

编写服务器端代码

编写客户端代码

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