gRPC的Java实现
Posted 早起的码农
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基本概念
gRPC具有以下特点：
（1）基于 HTTP/2， 继而提供了连接多路复用、Body 和 Header 压缩等机制。可以节省带宽、降低TCP链接次数、节省CPU使用和延长电池寿命等。
（2）支持主流开发语言（C, C++, Python, php, Ruby, NodeJS, C#, Objective-C、Golang、Java）
（3）IDL (Interface Definition Language) 层使用了 Protocol Buffers, 非常适合团队的接口设计
HelloWorld实例详解
gRPC的使用通常包括如下几个步骤：
通过protobuf来定义接口和数据类型
编写gRPC server端代码
编写gRPC client端代码
编写helloworld.proto
syntax = "proto3";
option java_multiple_files = true;
option java_package = "com.manong.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;
}
Maven配置
<properties>
<protobuf.version>3.12.0</protobuf.version>
<protoc.version>3.12.0</protoc.version>
<grpc.version>1.31.1</grpc.version>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>io.grpc</groupId>
<artifactId>grpc-bom</artifactId>
<version>1.31.1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>io.grpc</groupId>
<artifactId>grpc-protobuf</artifactId>
</dependency>
<dependency>
<groupId>io.grpc</groupId>
<artifactId>grpc-stub</artifactId>
</dependency>
<dependency>
<groupId>io.grpc</groupId>
<artifactId>grpc-services</artifactId>
</dependency>
<dependency>
<groupId>io.grpc</groupId>
<artifactId>grpc-netty-shaded</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<extensions>
<extension>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.6.2</version>
</extension>
</extensions>
<plugins>
<plugin>
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.6.1</version>
<configuration>
<protocArtifact>com.google.protobuf:protoc:${protoc.version}:exe:${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>
运行maven插件中下面命令，根据proto生成源代码
项目target下生成如下代码，实际项目上线后可以把该代码copy到对应src下面，把target下面的源码删除掉，这样也不用每次用maven中plugin去再生成代码。
Server端代码
import com.manong.grpc.helloworld.GreeterGrpc;
import com.manong.grpc.helloworld.HelloReply;
import com.manong.grpc.helloworld.HelloRequest;
import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;
import java.io.IOException;
import java.net.InetAddress;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
public class HostnameServer extends GreeterGrpc.GreeterImplBase {
private static final Logger logger = Logger.getLogger(HostnameServer.class.getName());
private final String serverName;
public HostnameServer(String serverName) {
if (serverName == null) {
serverName = determineHostname();
}
this.serverName = serverName;
}
@Override
public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
HelloReply reply = HelloReply.newBuilder()
.setMessage("Hello , " + req.getName() + ", from " + serverName)
.build();
responseObserver.onNext(reply);
responseObserver.onCompleted();
}
private static String determineHostname() {
try {
return InetAddress.getLocalHost().getHostName();
} catch (IOException ex) {
logger.log(Level.INFO, "Failed to determine hostname. Will generate one", ex);
}
// Strange. Well, let's make an identifier for ourselves.
return "generated-" + new Random().nextInt();
}
public void init() throws Exception {
int port = 50051;
String hostname = "0.0.0.0";
final Server server = ServerBuilder.forPort(port)
.addService(this)
.build()
.start();
System.out.println("Listening on port " + port);
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
server.shutdown();
try {
if (!server.awaitTermination(30, TimeUnit.SECONDS)) {
server.shutdownNow();
server.awaitTermination(5, TimeUnit.SECONDS);
}
} catch (InterruptedException ex) {
server.shutdownNow();
}
}
});
server.awaitTermination();
}
public static void main(String[] args) throws Exception {
HostnameServer hostnameServer = new HostnameServer("grpc server");
hostnameServer.init();
}
}
运行Server,出现如下输出表示Server已经正常启动
Client端代码
import com.manong.grpc.helloworld.GreeterGrpc;
import com.manong.grpc.helloworld.HelloReply;
import com.manong.grpc.helloworld.HelloRequest;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
public class HostnameClient {
public static void main(String[] args) {
String target = "localhost:50051";
ManagedChannel channel = ManagedChannelBuilder.forTarget(target).usePlaintext().build();
try {
GreeterGrpc.GreeterBlockingStub greeterBlockingStub = GreeterGrpc.newBlockingStub(channel);
//传参
HelloRequest defaultInstance = HelloRequest.newBuilder().setName("manong").build();
HelloReply helloReply = greeterBlockingStub.sayHello(defaultInstance);
System.out.println(helloReply.getMessage());
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行client端代码，出现如下输出，表示调用server服务成功并获得返回值
到此为止，一个完整的基于Java的gRpc demo就完成了。想了解更多可以猛击https://grpc.io/
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