GRPC学习之路(1)——初次上手

傷城~ 2022-05-25 02:40 201阅读 0赞

由于新工作中要使用grpc框架，之前也接触过一些，但是没有静下心来学它，加之网上对于这个方面的资料确实比较少，而且没有书，所以记录下来加深一下印象。

我主要参考的资料如下，当然也可以参考中文版的，但是感觉英文的还是更原汁原味吧。

[grpc的官网][grpc]

[gRPC 基础： Java][gRPC _ Java]

至于什么是grpc？它有什么特点之类的问题就不介绍了，官网及csdn的博客里有很多赘述。这里只记录一下如何上手做的一个简单的grpc服务实例，因为我发现官网的描述并不太直观，尤其是生成服务端很客户端代码部分有一些模糊。

## 准备工作 ##

准备好一个.proto的文件，这是定义rpc服务的关键文件，就以官网例子中的helloworld.proto为例。

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;
    }

## 生成代码 ##

有了.proto文件，有多种方式可以生成服务端和客户端的代码，这里采用protoc在maven中的插件生成的，pom.xml配置如下：

<?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>grpc-generate-test</groupId>
        <artifactId>grpc-generate-test</artifactId>
        <version>1.0-SNAPSHOT</version>
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <grpc.version>1.11.0</grpc.version>
            <netty.tcnative.version>2.0.7.Final</netty.tcnative.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>io.grpc</groupId>
                <artifactId>grpc-netty</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>${grpc.version}</version>
            </dependency>
        </dependencies>
        <build>
            <extensions>
                <extension>
                    <groupId>kr.motd.maven</groupId>
                    <artifactId>os-maven-plugin</artifactId>
                    <version>1.5.0.Final</version>
                </extension>
            </extensions>
            <plugins>
                <plugin>
                    <groupId>org.xolstice.maven.plugins</groupId>
                    <artifactId>protobuf-maven-plugin</artifactId>
                    <version>0.5.0</version>
                    <configuration>
                        <protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
                        <pluginId>grpc-java</pluginId>
                        <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${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>
    </project>

之后在命令行中输入命令：

**mvn compile**

如果成功则能在target目录找到对应生成好的代码文件：

![QQ20180506-181419_2x-300x146.png][]

## 实现服务端和客户端代码 ##

新建一个maven工程，将上面生成好的代码文件拷贝进去，新建一个GreeterService.java实现服务端的逻辑：

public class GreeterService extends GreeterGrpc.GreeterImplBase {
        @Override
        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
            HelloReply reply = HelloReply.newBuilder().setMessage("Hello2 " + req.getName()).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }

新建一个HelloWorldServer.java实现绑定端口号，注册服务的实现类等工作：

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 GreeterService())
            .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();
      }
    }

新建一个HelloWorldClient.java调用服务端的服务获得结果：

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(true)
            .build());
      }
    
      /** Construct client for accessing RouteGuide 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());
      }
    
      /**
       * 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();
        }
      }
    }

先运行服务端的代码，再执行客户端的代码，得到结果如下：

*五月 06, 2018 5:10:49 下午 HelloWorldClient greet  
信息: Will try to greet world ...  
五月 06, 2018 5:10:50 下午 HelloWorldClient greet  
信息: Greeting: Hello2 world*

至此完成了简单的从生成代码到实现具体服务功能的过程，之后如果有新的学习内容再继续总结。以下是博客里提到的工程文件，仅供参考

[grpcgeneratetest][]

[RouteGuideServer][]

欢迎关注我的个人的博客[www.zhijianliu.cn][], 虚心求教，有错误还请指正轻拍，谢谢

[grpc]: https://grpc.io/docs/tutorials/basic/java.html
[gRPC _ Java]: http://doc.oschina.net/grpc?t=60134
[QQ20180506-181419_2x-300x146.png]: http://www.zhijianliu.cn/wp-content/uploads/2018/05/QQ20180506-181419@2x-300x146.png
[grpcgeneratetest]: http://www.zhijianliu.cn/wp-content/uploads/2018/05/grpcgeneratetest.zip
[RouteGuideServer]: http://www.zhijianliu.cn/wp-content/uploads/2018/05/RouteGuideServer.zip
[www.zhijianliu.cn]: http://www.zhijianliu.cn/