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。
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><!-- CURRENT_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：
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
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
版权声明：本文出自志健的原创文章，未经博主允许不得转载
