Scala day 37 (scalapb)

project 目錄結構

build.sbt

import scalapb.compiler.Version.scalapbVersion

name := "hellopb"

scalaVersion := "2.11.12"

PB.targets in Compile := Seq(
  scalapb.gen() -> (sourceManaged in Compile).value
)

libraryDependencies ++= Seq(
 "com.thesamet.scalapb"  %%  "scalapb-runtime"       % scalapbVersion,
 "com.thesamet.scalapb"  %%  "scalapb-runtime-grpc"  % scalapbVersion,
 "io.grpc"               %   "grpc-okhttp"           % "1.14.0",
 "io.grpc"               %   "grpc-netty"            % "1.14.0"

)

assemblyJarName in assembly := name.value + ".jar"

assemblyMergeStrategy in assembly := {
    case PathList("META-INF", xs @ _*) => MergeStrategy.discard
    case x => MergeStrategy.first
}

assembly.sbt

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.7")

scalapb.sbt

addSbtPlugin("com.thesamet" % "sbt-protoc" % "0.99.18")
libraryDependencies += "com.thesamet.scalapb" %% "compilerplugin" % "0.7.4"

hello.proto

syntax = "proto3";

package com.example.protos;

// 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;
}

執行 sbt compile

build 出來的 scala 程式會在下列路徑

GreeterImpl.scala

package ght.mi.hello

import com.example.protos.hello.{GreeterGrpc, HelloReply, HelloRequest}

import scala.concurrent.Future

class GreeterImpl extends GreeterGrpc.Greeter {

  override def sayHello(req: HelloRequest) = {
    val reply = HelloReply(message = "Hello " + req.name)
    Future.successful(reply)
  }
}

HelloWorldServer.scala

package ght.mi.hello

import com.example.protos.hello.GreeterGrpc
import io.grpc.{Server, ServerBuilder}

import scala.concurrent.ExecutionContext

object HelloWorldServer {

  def main(args: Array[String]): Unit = {
    val server = new HelloWorldServer(ExecutionContext.global)
    server.start()
    server.blockUntilShutdown()
  }

  private val port = 50051
}

class HelloWorldServer(executionContext: ExecutionContext) {
  self =>
  private[this] var server: Server = null

  private def start(): Unit = {
    server = ServerBuilder.forPort(HelloWorldServer.port).addService(GreeterGrpc.bindService(new GreeterImpl, executionContext)).build.start

    sys.addShutdownHook {
      System.err.println("*** shutting down gRPC server since JVM is shutting down")
      self.stop()
      System.err.println("*** server shut down")
    }
  }

  private def stop(): Unit = {
    if (server != null) {
      server.shutdown()
    }
  }

  private def blockUntilShutdown(): Unit = {
    if (server != null) {
      server.awaitTermination()
    }
  }
}

HelloWorldClient.scala

package ght.mi.hello

import com.example.protos.hello.{GreeterGrpc, HelloReply, HelloRequest}
import io.grpc.ManagedChannelBuilder

object HelloWorldClient {

  def main(args: Array[String]): Unit = {
    val host = "localhost"
    val port = 50051
    val channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext(true).build
    val request = HelloRequest(name = "World")
    val blockingStub = GreeterGrpc.blockingStub(channel)
    val reply: HelloReply = blockingStub.sayHello(request)
    println(reply)
  }

}

測試

先執行 HelloWorldServer.scala 再執行 HelloWorldClient.scala

參考資料
scalapb