一、了解grpc

谷歌开源远程进程调用框架，支持多语言系统间通信，适用于各种分布式系统，使用http2协议并使用protobuf系列化通信数据，高性能。nacos2开始也集成了grpc，用于nacos server与nacos client间通信。grpc还支持了client-server双向流，两个流可独立不阻塞进行连续读写。

二、关于protobuf

如果只是protobuf作为序列化方案，建议使用protostuff（基于protobuf），不用写proto文件。grpc官方的quickstart都是直接使用protobuf，故这里暂不研究是否有grpc+protostuff方案。Java 有maven插件进行proto文件生成Java文件，故不用单独去安装proto了，但proto基本语法还得了解。

三、试玩grpc

官方的quickstart不是基于springboot的，故这里就参考这位大佬的JAVA使用gRPC
，为方便使用，这里server，client都在同一个工程里。如果要分开，则在独立项目中引入grpc-client-spring-boot-starter 等依赖并，并copy需要的类com.example.demo.protogen.UserServiceGrpc,com.example.demo.protogen.User等。

3.1整个工程目录

在这里插入图片描述

3.2 proto文件编写

proto里放file.proto,message.proto文件如下

syntax = "proto3";

package protogen;
option java_package = "com.example.demo.protogen";

message File {
  string name = 1;
  int32 size = 2;
}

syntax = "proto3";
package protogen;

import "file.proto";

option java_multiple_files = true;
option java_package = "com.example.demo.protogen";

message User {
  reserved 6 to 7;
  reserved "userId2";
  int32 userId = 1;
  string username = 2;
  oneof msg {
    string error = 3;
    int32 code = 4;
  }
  string name = 8;

  UserType userType = 9;
  repeated int32 roles = 10;

  protogen.File file = 11;
  map<string, string> hobbys = 12;
}

enum UserType {
  UNKNOW = 0;
  ADMIN = 1;
  BUSINESS_USER = 2;
};

service UserService {
  rpc getUser (User) returns (User) {}
  rpc getUsers (User) returns (stream User) {}
  rpc saveUsers (stream User) returns (User) {}
}

service FileService {
  rpc getFile(User) returns(File) {}
}

3.3 使用maven protobuf插件转换.proto文件

protogen里文件都是生成的，插件配置了读取这个目录，并生成到protogen文件夹里。通过点击如图插件按钮实现，protobuf:compile实际是通过proto.exe将.proto文件生成Java文件，除了FileServiceGrpc，UserServiceGrpc是protobuf:compile-custom生成的，其余都是protobuf:compile生成的。

3.4 Grpc服务端业务实现类

UserServiceImpl.java

package com.example.demo.grpc.server;

import com.example.demo.protogen.User;
import com.example.demo.protogen.UserServiceGrpc;
import io.grpc.stub.StreamObserver;
import net.devh.boot.grpc.server.service.GrpcService;

/**
 * @author Kone
 * @date 2022/1/29
 */
@GrpcService
public class UserServiceImpl extends UserServiceGrpc.UserServiceImplBase {
    @Override
    public void getUser(User request, StreamObserver<User> responseObserver) {
        System.out.println(request);
        User user = User.newBuilder()
                .setName("response name")
                .build();
        responseObserver.onNext(user);
        responseObserver.onCompleted();
    }

    @Override
    public void getUsers(User request, StreamObserver<User> responseObserver) {
        System.out.println("get users");
        System.out.println(request);
        User user = User.newBuilder()
                .setName("user1")
                .build();
        User user2 = User.newBuilder()
                .setName("user2")
                .build();
        responseObserver.onNext(user);
        responseObserver.onNext(user2);

        responseObserver.onCompleted();
    }

    @Override
    public StreamObserver<User> saveUsers(StreamObserver<User> responseObserver) {

        return new StreamObserver<User>() {
            @Override
            public void onNext(User user) {
                System.out.println("get saveUsers list ---->");
                System.out.println(user);
            }

            @Override
            public void onError(Throwable throwable) {
                System.out.println("saveUsers error " + throwable.getMessage());
            }

            @Override
            public void onCompleted() {
                User user = User.newBuilder()
                        .setName("saveUsers user1")
                        .build();
                responseObserver.onNext(user);
                responseObserver.onCompleted();
            }
        };
    }
}

3.5 pom参考

springboot3有点问题，暂用2.7.9版本springboot

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.9</version>
        <relativePath/> 
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>17</java.version>
        <protobuf.version>3.23.4</protobuf.version>
        <grpc.version>1.26.0</grpc.version>
    </properties>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/com.google.protobuf/protobuf-java -->
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>${protobuf.version}</version>
        </dependency>
        <!-- grpc server和spring-boot集成框架 -->
        <dependency>
            <groupId>net.devh</groupId>
            <artifactId>grpc-server-spring-boot-starter</artifactId>
            <version>2.14.0.RELEASE</version>
        </dependency>

        <!-- grpc client和spring-boot集成框架 -->
        <dependency>
            <groupId>net.devh</groupId>
            <artifactId>grpc-client-spring-boot-starter</artifactId>
            <version>2.14.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>
    </dependencies>

    <build>

        <!-- os系统信息插件, protobuf-maven-plugin需要获取系统信息下载相应的protobuf程序 -->
        <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>
                    <!--os.detected.classifier属性是通过如上os-maven-plugin插件获取的-->
                    <protocArtifact>com.google.protobuf:protoc:${protobuf.version}:exe:${os.detected.classifier}
                    </protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}
                    </pluginArtifact>

                    <!-- proto文件目录 -->
                    <protoSourceRoot>${project.basedir}/src/main/java/com/example/demo/proto</protoSourceRoot>
                    <!-- 生成的Java文件目录,这里指定到这一级就可以咯，proto文件有基于package指定 -->
                    <outputDirectory>${project.basedir}/src/main/java</outputDirectory>
                    <clearOutputDirectory>false</clearOutputDirectory>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>17</source>
                    <target>17</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3.6 grpc client调用

基于grpc server的URL直接调用

package com.example.demo;

import com.example.demo.protogen.User;
import com.example.demo.protogen.UserServiceGrpc;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Iterator;

public class FramelessGrpcClient {

    public static void main(String[] args) {
        ManagedChannel managedChannel = ManagedChannelBuilder.forAddress("localhost", 9090).usePlaintext().build();
        UserServiceGrpc.UserServiceBlockingStub userService = UserServiceGrpc.newBlockingStub(managedChannel);
        User user = User.newBuilder()
                .setUserId(100)
                .putHobbys("pingpong", "play pingpong")
                .setCode(200)
                .build();
        System.out.println("get response-------->");
        System.out.println(userService.getUser(user));
        Iterator<User> users = userService.getUsers(user);
    }
}

从spring IOC注入bean来调用grpc server (yml里配置了URL等)。这里使用定时任务来触发调度。注意注入的“userClient”需要与yml 自定义的client名一致（如果调用多个grpc server，这个自定义名就是用来区别调用哪个grpc server滴）。

package com.example.demo;

import com.example.demo.protogen.User;
import com.example.demo.protogen.UserServiceGrpc;
import net.devh.boot.grpc.client.inject.GrpcClient;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.util.Iterator;

/**
 * TODO
 *
 * @author majun
 * @version 1.0
 * @since 2023-08-02 20:19
 */
@Component
@EnableScheduling
public class SpringbootGrpcClient {
    @GrpcClient("userClient")
    private UserServiceGrpc.UserServiceBlockingStub userService;


    @Scheduled(fixedDelay = 10000)
    public void test() {
        User user = User.newBuilder()
                .setUserId(100)
                .putHobbys("pingpong", "play pingpong")
                .setCode(200)
                .build();
        System.out.println("get response-------->");
        System.out.println(userService.getUser(user));

        Iterator<User> users = this.userService.getUsers(user);
        while (users.hasNext()) {
            System.out.println(users.next());
        }
    }
}