IDL 定义跨语言服务
- 前置条件
- 创建工程

IDL 定义跨语言服务

从零演示如何基于 IDL 方式来定义 Dubbo 服务并使用 Triple 协议

使用 IDL 定义服务具有更好的跨语言友好性，对于 Dubbo3 新用户而言，我们推荐使用这种方式。然而 Triple 协议并不是和 IDL 强绑定的，也可以使用 Java Interface + Pojo 的方式定义服务并启用 Triple 协议，具体可参见示例。

更多 Triple 和 IDL 使用方式，请参考官方示例

前置条件

JDK 版本 >= 8
已安装 Maven

创建工程

首先创建一个空的 maven 工程

$ mvn archetype:generate                                \
    -DgroupId=org.apache.dubbo                          \
    -DartifactId=tri-stub-demo                          \
    -DarchetypeArtifactId=maven-archetype-quickstart    \
    -DarchetypeVersion=1.4                              \
    -DarchetypeGroupId=org.apache.maven.archetypes      \
    -Dversion=1.0-SNAPSHOT

切换到工程目录
```
$ cd tri-stub-demo
```

在 pom.xml 中设置 JDK 版本，添加 Dubbo 依赖和插件

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
   <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.13</version>
       <scope>test</scope>
   </dependency>
   <dependency>
       <groupId>org.apache.dubbo</groupId>
       <artifactId>dubbo</artifactId>
       <version>3.0.8</version>
   </dependency>
   <dependency>
    <groupId>org.apache.dubbo</groupId>
    <artifactId>dubbo-dependencies-zookeeper-curator5</artifactId>
    <type>pom</type>
    <version>3.0.8</version>
   </dependency>
    <dependency>
        <groupId>com.google.protobuf</groupId>
        <artifactId>protobuf-java</artifactId>
        <version>3.19.4</version>
    </dependency>
</dependencies>
<build>
    <extensions>
        <extension>
            <groupId>kr.motd.maven</groupId>
            <artifactId>os-maven-plugin</artifactId>
            <version>1.6.1</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:3.19.4:exe:${os.detected.classifier}</protocArtifact>
                <protocPlugins>
                    <protocPlugin>
                        <id>dubbo</id>
                        <groupId>org.apache.dubbo</groupId>
                        <artifactId>dubbo-compiler</artifactId>
                        <version>0.0.4.1-SNAPSHOT</version>
                        <mainClass>org.apache.dubbo.gen.tri.Dubbo3TripleGenerator</mainClass>
                    </protocPlugin>
                </protocPlugins>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

添加接口定义文件src/main/proto/hello.proto，Dubbo 使用 Protobuf 作为 IDL

syntax = "proto3";
option java_multiple_files = true;
option java_package = "org.apache.dubbo.hello";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";
package helloworld;
message HelloRequest {
    string name = 1;
}
message HelloReply {
    string message = 1;
}
service Greeter{
    rpc greet(HelloRequest) returns (HelloReply);
}

编译 IDL

$ mvn clean install

编译成功后，可以看到target/generated-sources/protobuf/java 目录下生成了代码文件

$ ls org/apache/dubbo/hello/
DubboGreeterTriple.java    HelloReply.java            HelloRequest.java          HelloWorldProto.java
Greeter.java               HelloReplyOrBuilder.java   HelloRequestOrBuilder.java

添加服务端接口实现src/main/java/org/apache/dubbo/GreeterImpl.java

package org.apache.dubbo;
import org.apache.dubbo.hello.DubboGreeterTriple;
import org.apache.dubbo.hello.HelloReply;
import org.apache.dubbo.hello.HelloRequest;
public class GreeterImpl extends DubboGreeterTriple.GreeterImplBase {
   @Override
   public HelloReply greet(HelloRequest request) {
      return HelloReply.newBuilder()
      .setMessage("Hello," + request.getName() + "!")
      .build();
   }
}

添加服务端启动类 src/main/java/org/apache/dubbo/MyDubboServer.java

package org.apache.dubbo;
import org.apache.dubbo.common.constants.CommonConstants;
import org.apache.dubbo.config.ApplicationConfig;
import org.apache.dubbo.config.ProtocolConfig;
import org.apache.dubbo.config.RegistryConfig;
import org.apache.dubbo.config.ServiceConfig;
import org.apache.dubbo.config.bootstrap.DubboBootstrap;
import org.apache.dubbo.hello.Greeter;
import java.io.IOException;
public class MyDubboServer {
   public static void main(String[] args) throws IOException {
       ServiceConfig<Greeter> service = new ServiceConfig<>();
       service.setInterface(Greeter.class);
       service.setRef(new GreeterImpl());
       DubboBootstrap bootstrap = DubboBootstrap.getInstance();
       bootstrap.application(new ApplicationConfig("tri-stub-server"))
               .registry(new RegistryConfig("multicast://127.0.0.1:2181"))
               .protocol(new ProtocolConfig(CommonConstants.TRIPLE, 50051))
               .service(service)
               .start();
       System.out.println("Dubbo triple stub server started");
       System.in.read();
   }
}

添加客户端启动类src/main/java/org/apache/dubbo/MyDubboClient.java

package org.apache.dubbo;
import org.apache.dubbo.common.constants.CommonConstants;
import org.apache.dubbo.config.ApplicationConfig;
import org.apache.dubbo.config.ReferenceConfig;
import org.apache.dubbo.config.RegistryConfig;
import org.apache.dubbo.config.bootstrap.DubboBootstrap;
import org.apache.dubbo.hello.Greeter;
import org.apache.dubbo.hello.HelloReply;
import org.apache.dubbo.hello.HelloRequest;
public class MyDubboClient {
   public static void main(String[] args) {
      DubboBootstrap bootstrap = DubboBootstrap.getInstance();
      ReferenceConfig<Greeter> ref = new ReferenceConfig<>();
      ref.setInterface(Greeter.class);
      ref.setProtocol(CommonConstants.TRIPLE);
      ref.setProxy(CommonConstants.NATIVE_STUB);
      ref.setTimeout(3000);
      bootstrap.application(new ApplicationConfig("tri-stub-client"))
         .registry(new RegistryConfig("zookeeper://127.0.0.1:2181"))
         .reference(ref)
         .start();
      Greeter greeter = ref.get();
      HelloRequest request = HelloRequest.newBuilder().setName("Demo").build();
      HelloReply reply = greeter.greet(request);
      System.out.println("Received reply:" + reply);
    }
}

编译代码
```
$ mvn clean install
```
启动服务端

$ mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="org.apache.dubbo.MyDubboServer"
Dubbo triple stub server started

打开新的终端，启动客户端

$ mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="org.apache.dubbo.MyDubboClient"
Received reply:message: "Hello,Demo!"

最后修改 December 16, 2022: Fix check (#1736) (97972c1)