SpringBoot + Kotlin 中使用 GRPC 进行服务通信

示例项目见：kotlin-grpc

一、导入依赖：

import com.google.protobuf.gradle.*  
  
plugins {
    
      
    id("org.springframework.boot") version "2.3.1.RELEASE"  
    id("io.spring.dependency-management") version "1.0.9.RELEASE"  
    id("org.asciidoctor.convert") version "1.5.9.2"  
    kotlin("jvm") version "1.6.0"  
    kotlin("plugin.spring") version "1.6.0"  
    id("com.google.protobuf") version "0.9.2"  
}  
  
repositories {
    
      
    mavenCentral()  
}  
  
group = "com.whrss.kotlin-grpc"  
version = "0.0.1-SNAPSHOT"  
  
java.sourceCompatibility = JavaVersion.VERSION_1_8  
java.targetCompatibility = JavaVersion.VERSION_1_8  
  
sourceSets.main {
    
      
    java.srcDirs("src/main/kotlin")  
}  
  
extra["spring-restdocs.version"] = "2.0.5.BUILD-SNAPSHOT"  
val snippetsDir by extra {
    
     file("build/generated-snippets") }  
  
dependencies {
    
      
    implementation("com.google.protobuf:protobuf-java:3.22.2")  
    implementation("io.grpc:grpc-protobuf:1.53.0")  
    implementation("com.google.protobuf:protobuf-kotlin:3.22.2")  
    implementation("io.grpc:grpc-kotlin-stub:1.3.0")  
    implementation("io.grpc:grpc-netty:1.56.1")  
    implementation("io.grpc:grpc-all:1.56.1")  
}  
  
protobuf {
    
      
    protoc {
    
      
        artifact = "com.google.protobuf:protoc:3.19.4"  
    }  
    plugins {
    
      
        id("grpc") {
    
      
            artifact = "io.grpc:protoc-gen-grpc-java:1.40.1"  
        }  
        id("grpckt") {
    
      
            artifact = "io.grpc:protoc-gen-grpc-kotlin:1.3.0:jdk8@jar"  
        }  
    }  
    // Enable Kotlin generation  
    generateProtoTasks {
    
      
        all().forEach {
    
      
            it.plugins {
    
      
                id("grpc")  
                id("grpckt")  
            }  
        }    }}

二、设置Proto

将 proto 文件放在 src/mian/proto 目录下

syntax = "proto3";  
import "google/api/annotations.proto";  
option java_multiple_files = true;  
package hello_world.v1;  
service HelloWorldService{  
  rpc GetUserInfo (GetUserRequest) returns (GetUserReply) {  
    option (google.api.http) = {  
      get: "/api/v1/users"  
    };  
  }  
}  
message GetUserRequest{  
  // 用户showId  
  string userId = 1;  
}  
message GetUserReply{  
  // 用户showId  
  string userId = 1;  
}

执行 ./gradlew clean build

build成功则会在 build/generated/source/proto/main 下生成对应的 grpc 、 grpckt 、 java 文件
在程序中可以直接导包引入

三、Server端

写一个 service

import hello_world.v1.GetUserReply  
import hello_world.v1.GetUserRequest  
import hello_world.v1.HelloWorldServiceGrpcKt  
  
  
class Service : HelloWorldServiceGrpcKt.HelloWorldServiceCoroutineImplBase() {
    
      
  
    override suspend fun getUserInfo(request: GetUserRequest) : GetUserReply {
    
      
        println("getItemStatistics exec")  
        return GetUserReply.newBuilder()  
            .setUserId(request.userId)  
            .build()  
    }  
  
}

在 main 入口引入启动

import io.grpc.ServerBuilder  
  
  
fun main() {
    
      
    helloServer()  
}  
fun helloServer() {
    
      
    val helloService = Service()  
    val server = ServerBuilder  
        .forPort(15001)  
        .addService(helloService)  
        .build()  
  
    Runtime.getRuntime().addShutdownHook(Thread {
    
      
        server.shutdown()  
        server.awaitTermination()  
    })  
  
    server.start()  
    println("server start")  
    server.awaitTermination()  
    println("server restart")  
}

四、Client 端

import hello_world.v1.GetUserRequest  
import hello_world.v1.HelloWorldServiceGrpc  
import io.grpc.ManagedChannelBuilder  
  
  
fun main() {
    
      
    val channel = ManagedChannelBuilder.forAddress("localhost", 15001).usePlaintext()  
    val stub = HelloWorldServiceGrpc.newBlockingStub(channel.build())  
    val response = stub.getUserInfo(GetUserRequest.newBuilder().setUserId("0").build())  
    println(response)  
}

五、一些坑

io.grpc 和 com.google的一些依赖是有关联的，如果依赖版本之间有巨大差异，是会导致运行错误的。比如我之前使用到了一个 google 的一个特别老的依赖：com.google.code.google-collections:google-collect:snapshot-20080530，导致了我程序运行时提示：

Exception in thread "main" java.lang.NoSuchMethodError: 'void com.google.common.base.Preconditions.checkArgument(boolean, java.lang.String, char, java.lang.Object)'
	at io.grpc.Metadata$Key.validateName(Metadata.java:754)
	at io.grpc.Metadata$Key.<init>(Metadata.java:762)
	at io.grpc.Metadata$Key.<init>(Metadata.java:671)
	at io.grpc.Metadata$AsciiKey.<init>(Metadata.java:971)
	at io.grpc.Metadata$AsciiKey.<init>(Metadata.java:966)
	at io.grpc.Metadata$Key.of(Metadata.java:708)
	at io.grpc.Metadata$Key.of(Metadata.java:704)
	at io.grpc.internal.GrpcUtil.<clinit>(GrpcUtil.java:99)
	at io.grpc.netty.Utils.<clinit>(Utils.java:83)
	at io.grpc.netty.UdsNettyChannelProvider.isAvailable(UdsNettyChannelProvider.java:34)
	at io.grpc.ManagedChannelRegistry$ManagedChannelPriorityAccessor.isAvailable(ManagedChannelRegistry.java:211)
	at io.grpc.ManagedChannelRegistry$ManagedChannelPriorityAccessor.isAvailable(ManagedChannelRegistry.java:207)
	at io.grpc.ServiceProviders.loadAll(ServiceProviders.java:68)
	at io.grpc.ManagedChannelRegistry.getDefaultRegistry(ManagedChannelRegistry.java:101)
	at io.grpc.ManagedChannelProvider.provider(ManagedChannelProvider.java:43)
	at io.grpc.ManagedChannelBuilder.forAddress(ManagedChannelBuilder.java:39)
	at com.ck567.kotlingrpc.ClientKt.main(Client.kt:9)
	at com.ck567.kotlingrpc.ClientKt.main(Client.kt)

在google是发现不了具体的问题的，可以注意一下，在项目中查看下是否有别的com.google的依赖。

上面的依赖版本都是基于对应 spring boot 和 kotlin 版本的，如果你的版本不适配，可能也需要折腾一下，但问题应该不是很大。使用阿里云的镜像仓库，可以直接在这里搜索镜像，查看支持的版本。

---

gradle 打包出现问题，问题原因是Bintray/jcenter 已停用，要依赖这些 kotlin 插件可以使用阿里云的镜像中的依赖。

A problem occurred configuring root project 'yybs-backend'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not resolve org.jetbrains.kotlin:kotlin-gradle-plugin-api:1.6.0.
     Required by:
         project : > org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin:1.6.0 > org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.0
         project : > org.jetbrains.kotlin.plugin.spring:org.jetbrains.kotlin.plugin.spring.gradle.plugin:1.6.0 > org.jetbrains.kotlin:kotlin-allopen:1.6.0
      > Could not resolve org.jetbrains.kotlin:kotlin-gradle-plugin-api:1.6.0.
         ..........
         
    > sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

找到对应的～/.gradle 目录，创建或修改 init.gradle 内容为下面的内容

allprojects {
    
    
    repositories {
    
    
        maven {
    
    
            url 'https://maven.aliyun.com/repository/public/'
        }
        maven {
    
    
            url 'https://maven.aliyun.com/repository/jcenter/'
        }
        all {
    
     ArtifactRepository repo ->
            if (repo instanceof MavenArtifactRepository) {
    
    
                def url = repo.url.toString()

                if (
url.startsWith('https://repo.maven.apache.org/maven2/')
|| url.startsWith('https://repo.maven.org/maven2')
|| url.startsWith('https://repo1.maven.org/maven2')
|| url.startsWith('https://jcenter.bintray.com/')
|| url.startsWith('https://plugins.gradle.org/')
) {
    
    
                    //project.logger.lifecycle "Repository ${repo.url} replaced by $REPOSITORY_URL."
                    remove repo
                }
            }
        }
    }

    buildscript {
    
    

        repositories {
    
    

            maven{
    
     url 'https://maven.aliyun.com/repository/public/'}

            maven {
    
    
                url 'https://maven.aliyun.com/repository/jcenter/'
            }

            maven {
    
    
                url 'https://maven.aliyun.com/repository/gradle-plugin/'
            }
            all {
    
     ArtifactRepository repo ->
                if (repo instanceof MavenArtifactRepository) {
    
    
                    def url = repo.url.toString()
                    if (
url.startsWith('https://repo1.maven.org/maven2')
|| url.startsWith('https://jcenter.bintray.com/')
|| url.startsWith('https://plugins.gradle.org/')
) {
    
    
                        //project.logger.lifecycle "Repository ${repo.url} replaced by $REPOSITORY_URL."
                        remove repo
                    }
                }
            }
        }
    }

}

---

--grpckt_out: protoc-gen-grpckt: Plugin failed with status code 1

Execution failed for task ':generateProto'.
> protoc: stdout: . stderr: Exception in thread "main" java.lang.VerifyError: Uninitialized object exists on backward branch 71
  Exception Details:
    Location:
      com/squareup/kotlinpoet/TypeSpec.<init>(Lcom/squareup/kotlinpoet/TypeSpec$Builder;Lcom/squareup/kotlinpoet/TagMap;Lcom/squareup/kotlinpoet/OriginatingElementsHolder;ILkotlin/jvm/internal/DefaultConstructorMarker;)V @118: goto
    Reason:
      Error exists in the bytecode
    Bytecode:
      0000000: 1504 057e 9900 0b2b c003 44b8 034a 4d15
      0000010: 0407 7e99 007e 2bb6 00de c000 9a2b b600
      0000020: c4c0 009c 3a06 3a0f 0336 0719 063a 08bb
      0000030: 0152 59b7 01c3 c000 9a3a 0903 360a 1908
      0000040: b901 5c01 003a 0b19 0bb9 0161 0100 9900
      0000050: 2b19 0bb9 0165 0100 3a0c 190c 3a0d 0336
      0000060: 0e19 0dc0 0002 b600 dfc0 009c 3a0d 1909
      0000070: 190d b800 a257 a7ff d119 09c0 016e 3a10
      0000080: 190f 1910 c000 9cb8 0172 b803 50c0 0008
      0000090: 4e2a 2b2c 2db7 0352 b1                 
    Stackmap Table:
      same_frame(@15)
      full_frame(@71,{
    
    UninitializedThis,Object[#144],Object[#218],Object[#8],Integer,Object[#857],Object[#156],Integer,Object[#156],Object[#154],Integer,Object[#350],Top,Top,Top,Object[#154]},{})
      same_frame(@121)
      full_frame(@145,{
    
    UninitializedThis,Object[#144],Object[#218],Object[#8],Integer,Object[#857]},{})
  
  	at io.grpc.kotlin.generator.GrpcClientStubGenerator.generateStub(GrpcClientStubGenerator.kt:111)
  	at io.grpc.kotlin.generator.GrpcClientStubGenerator.generate(GrpcClientStubGenerator.kt:100)
  	at io.grpc.kotlin.generator.ProtoFileCodeGenerator.generateCodeForFile(ProtoFileCodeGenerator.kt:50)
  	at io.grpc.kotlin.generator.GeneratorRunner.generateCodeForFile(GeneratorRunner.kt:44)
  	at io.grpc.kotlin.generator.protoc.AbstractGeneratorRunner.mainAsProtocPlugin(AbstractGeneratorRunner.kt:56)
  	at io.grpc.kotlin.generator.protoc.AbstractGeneratorRunner.doMain(AbstractGeneratorRunner.kt:87)
  	at io.grpc.kotlin.generator.GeneratorRunner.main(GeneratorRunner.kt:28)
  --grpckt_out: protoc-gen-grpckt: Plugin failed with status code 1.

升级 java 版本，我升级到了最新的 jdk-8u221

如有问题，欢迎留言，能帮到的地方，我不会吝啬。