通过dubbo暴露grpc服务本质还是借助 java-grpc 来实现的，我们想通过dubbo发布一个grpc服务，需要以下步骤：

1. 定义一个 xx.proto 文件： 里面定义了参数的结构及对应的RPC服务
2. 通过 protobuf-maven-plugin 插件，生成对应的java文件
3. 在应用中添加grpc相关的配置启用grpc服务

定义proro文件

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;
}

添加相关依赖

<dependency>
    <groupId>org.apache.dubbo</groupId>
    <artifactId>dubbo</artifactId>
</dependency>
<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-netty</artifactId>
    <version>${grpc.version}</version>
</dependency>
<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-netty-shaded</artifactId>
    <version>${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>
<dependency>
    <groupId>com.google.protobuf</groupId>
    <artifactId>protobuf-java-util</artifactId>
    <version>3.6.1</version>
</dependency>

添加相关插件

<build>
    <extensions>
        <extension>
            <groupId>kr.motd.maven</groupId>
            <artifactId>os-maven-plugin</artifactId>
            <version>1.6.1</version>
        </extension>
    </extensions>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.7.0</version>
            <configuration>
                <source>${maven.compiler.source}</source>
                <target>${maven.compiler.target}</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.xolstice.maven.plugins</groupId>
            <artifactId>protobuf-maven-plugin</artifactId>
            <version>0.6.1</version>
            <configuration>
                <protocArtifact>com.google.protobuf:protoc:3.7.1:exe:${os.detected.classifier}</protocArtifact>
                <pluginId>grpc-java</pluginId>
                <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}
                </pluginArtifact>
                <outputDirectory>build/java</outputDirectory>
                <clearOutputDirectory>false</clearOutputDirectory>
                <protocPlugins>
                    <protocPlugin>
                        <id>dubbo-grpc</id>
                        <groupId>org.apache.dubbo</groupId>
                        <artifactId>dubbo-compiler</artifactId>
                        <version>${dubbo.compiler.version}</version>
                        <mainClass>org.apache.dubbo.gen.grpc.DubboGrpcGenerator</mainClass>
                    </protocPlugin>
                </protocPlugins>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>compile-custom</goal>
                        <goal>test-compile</goal>
                        <goal>test-compile-custom</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>build-helper-maven-plugin</artifactId>
            <executions>
                <execution>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>add-source</goal>
                    </goals>
                    <configuration>
                        <sources>
                            <source>build/java</source>
                        </sources>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

打包依赖

helloworld.proto文件经过上述插件编译之后，会生成对应的java代码，其中包括： 请求参数实体、响应参数实体、对应RPC接口。然后我们将这些java代码，打包成一个client.jar依赖，最后在consuemr和provider端引用这个依赖，和平时使用dubbo是一样的。

最后生成的java文件如下：

提供端配置

// 配置ProtocolConfig
@Bean
public ProtocolConfig protocolConfig() {
    ProtocolConfig protocolConfig = new ProtocolConfig();
//  protocolConfig.setName("dubbo");
    protocolConfig.setName("grpc");
    protocolConfig.setPort(20880);
    return protocolConfig;
}



// 定义实现类，注意这里的 DubboGreeterGrpc.GreeterImplBase 是基于 proto文件 自动生成的
public class GrpcGreeterImpl extends DubboGreeterGrpc.GreeterImplBase {

    @Override
    public void sayHello(HelloRequest request, StreamObserver<HelloReply> responseObserver) {
        System.out.println("Executing thread is " + Thread.currentThread().getName());
        HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + request.getName()).build();
        responseObserver.onNext(reply);
        responseObserver.onCompleted();
    }

}


// 暴露服务
<bean id="greeterImpl" class="com.tuya.grpc.test.provider.impl.GrpcGreeterImpl"/>
<dubbo:service interface="io.grpc.examples.helloworld.DubboGreeterGrpc$IGreeter" ref="greeterImpl" protocol="grpc"/>

消费端配置

@Bean
public ProtocolConfig protocolConfig() {
    ProtocolConfig protocolConfig = new ProtocolConfig();
    protocolConfig.setName("grpc");
    return protocolConfig;
}


// 引用服务， 注意这里要添加  protocol = "grpc"
@DubboReference(protocol = "grpc")
private DubboGreeterGrpc.IGreeter greeter;