ScalaPB(4): 通用跨系统protobuf数据,sbt设置

BitTigerio 2018-05-13

我们知道,在集群环境节点之间进行交换的数据必须经过序列化/反序列化处理过程,而在这方面protobuf是一个比较高效、易用的模式。用户首先在.proto文件中用IDL来定义系统中各种需要进行交换的数据类型。然后用protoc编译器自动产生相关的源代码,里面包括了完整的序列化处理函数。在一个集成的系统环境内,protobuf数据必须保持与所有系统的松散耦合,不能对这些用户系统有任何依赖。这样把protobuf数据类型和相关的序列化/反序列化函数打成一个独立的包,由用户系统各自引用就是一种最佳解决方案了。

下面示范产生一个独立的protobuf包。build.sbt定义如下:

import scalapb.compiler.Version.scalapbVersion
import scalapb.compiler.Version.grpcJavaVersion

name := "common-protobuf-data"

version := "0.1"

scalaVersion := "2.12.6"

libraryDependencies ++= Seq(
  "com.thesamet.scalapb" %% "scalapb-runtime" % scalapbVersion % "protobuf",
  "io.grpc" % "grpc-netty" % grpcJavaVersion,
  "com.thesamet.scalapb" %% "scalapb-runtime-grpc" % scalapbVersion
)

PB.targets in Compile := Seq(
  scalapb.gen(
    flatPackage = true
  ) -> (sourceDirectory in Compile).value / "scala/generated"

)

注意我们指定把产生的源代码放在src/main/scala/generated/目录下。

我们再随便建个.proto文件:

syntax = "proto3";

// Brought in from scalapb-runtime
import "scalapb/scalapb.proto";
import "google/protobuf/wrappers.proto";

package proto.microservices;

message Added {

    int32 nbr1 = ;
    int32 nbr2 = ;
}

message Subtracted {
    int32 nbr1 = ;
    int32 nbr2 = ;
}

message AddedResult {
    int32 nbr1 = ;
    int32 nbr2 = ;
    int32 result = ;
}

message SubtractedResult {
    int32 nbr1 = ;
    int32 nbr2 = ;
    int32 result = ;
}

用sbt package 产生common-protobuf-data_???.jar文件。在使用方sbt项目里可以用unmanagedBase指定.jar路径或者把包放到默认的lib/目录下:

lazy val commonSettings = Seq(
  name := "using-common-protobuf-data",
  version := "1.0",
  scalaVersion := "2.12.6",
)

lazy val local = (project in file("."))
  .settings(commonSettings)
  .settings(
    libraryDependencies ++= Seq(
      "com.typesafe.akka"      %% "akka-remote" % "2.5.11",
      "com.thesamet.scalapb" %% "scalapb-runtime" % scalapb.compiler.Version.scalapbVersion % "protobuf"
    ),
  )

unmanagedBase := file("/users/tiger-macpro/jars/")

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

好了。在上面的.sbt文件中有关路径的设置需要总结一下:

1、改变默认源代码路径: (src/main/scala, src/test/scala)

scalaSource in Compile := baseDirectory.value / "src"
scalaSource in Test := baseDirectory.value / "test-src"

javaSource in Compile := baseDirectory.value / "src"
javaSource in Test := baseDirectory.value / "test-src"

2、改变默认资源路径:(src/main/resources)

resourceDirectory in Compile := baseDirectory.value / "resources"
resourceDirectory in Test := baseDirectory.value / "test-resources"

3、改变默认附加库路径:(lib/)

unmanagedBase := baseDirectory.value / "jars"
//只在编译时引用
unmanagedBase in Compile := baseDirectory.value / "lib" / "main"

4、取消根目录为源代码默认路径:

sourcesInBase := false

5、增加一个源代码路径:

unmanagedSourceDirectories in Compile += baseDirectory.value / "extra-src"

6、增加一个资源路径:

unmanagedResourceDirectories in Compile += baseDirectory.value / "extra-resources"

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