.sbt 构建可以补充 project/*.scala 文件。当构建文件变得足够大时,第一个要提取的是解析器和依赖项。
import sbt._
import Keys._
object Resolvers {
  val sunrepo    = "Sun Maven2 Repo" at "http://download.java.net/maven/2"
  val sunrepoGF  = "Sun GF Maven2 Repo" at "http://download.java.net/maven/glassfish" 
  val oraclerepo = "Oracle Maven2 Repo" at "http://download.oracle.com/maven"
  val oracleResolvers = Seq(sunrepo, sunrepoGF, oraclerepo)
}
import sbt._
import Keys._
object Dependencies {
  val logbackVersion = "0.9.16"
  val grizzlyVersion = "1.9.19"
  val logbackcore    = "ch.qos.logback" % "logback-core"     % logbackVersion
  val logbackclassic = "ch.qos.logback" % "logback-classic"  % logbackVersion
  val jacksonjson = "org.codehaus.jackson" % "jackson-core-lgpl" % "1.7.2"
  val grizzlyframwork = "com.sun.grizzly" % "grizzly-framework" % grizzlyVersion
  val grizzlyhttp     = "com.sun.grizzly" % "grizzly-http"      % grizzlyVersion
  val grizzlyrcm      = "com.sun.grizzly" % "grizzly-rcm"       % grizzlyVersion
  val grizzlyutils    = "com.sun.grizzly" % "grizzly-utils"     % grizzlyVersion
  val grizzlyportunif = "com.sun.grizzly" % "grizzly-portunif"  % grizzlyVersion
  val sleepycat = "com.sleepycat" % "je" % "4.0.92"
  val apachenet   = "commons-net"   % "commons-net"   % "2.0"
  val apachecodec = "commons-codec" % "commons-codec" % "1.4"
  val scalatest = "org.scalatest" %% "scalatest" % "3.2.17"
}
这些文件可用于在一个地方管理库依赖项。
当您想要实现自定义命令或任务时,可以通过定义一个一次性自动插件来组织构建。
import sbt._
import Keys._
import scala.sys.process._
// Shell prompt which show the current project and git branch
object ShellPromptPlugin extends AutoPlugin {
  override def trigger = allRequirements
  override lazy val projectSettings = Seq(
    shellPrompt := buildShellPrompt
  )
  val devnull: ProcessLogger = new ProcessLogger {
    def out(s: => String): Unit = {}
    def err(s: => String): Unit = {}
    def buffer[T] (f: => T): T = f
  }
  def currBranch =
    ("git status -sb" lineStream_! devnull headOption)
      .getOrElse("-").stripPrefix("## ")
  val buildShellPrompt: State => String = {
    case (state: State) =>
      val currProject = Project.extract (state).currentProject.id
      s"""$currProject:$currBranch> """
  }
}
此自动插件将显示当前项目名称和 git 分支。
现在我们已将自定义设置和依赖项提取到 project/*.scala,我们可以在 build.sbt 中使用它们。
import Resolvers._
import Dependencies._
// factor out common settings into a sequence
lazy val buildSettings = Seq(
  organization := "com.example",
  version := "0.1.0",
  scalaVersion := "2.12.18"
)
// Sub-project specific dependencies
lazy val commonDeps = Seq(
  logbackcore,
  logbackclassic,
  jacksonjson,
  scalatest % Test
)
lazy val serverDeps = Seq(
  grizzlyframwork,
  grizzlyhttp,
  grizzlyrcm,
  grizzlyutils,
  grizzlyportunif,
  sleepycat,
  scalatest % Test
)
lazy val pricingDeps = Seq(
  apachenet,
  apachecodec,
  scalatest % Test
)
lazy val cdap2 = (project in file("."))
  .aggregate(common, server, compact, pricing, pricing_service)
  .settings(buildSettings)
lazy val common = (project in file("cdap2-common"))
  .settings(
    buildSettings,
    libraryDependencies ++= commonDeps
  )
lazy val server = (project in file("cdap2-server"))
  .dependsOn(common)
  .settings(
    buildSettings,
    resolvers := oracleResolvers,
    libraryDependencies ++= serverDeps
  )
lazy val pricing = (project in file("cdap2-pricing"))
  .dependsOn(common, compact, server)
  .settings(
    buildSettings,
    libraryDependencies ++= pricingDeps
  )  
lazy val pricing_service = (project in file("cdap2-pricing-service"))
  .dependsOn(pricing, server)
  .settings(buildSettings)
lazy val compatct = (project in file("compact-hashmap"))
  .settings(buildSettings)