课程涵盖了SBT!详细主题包括:

关于SBT

SBT 是一个流行的构建工具。它是用Scala 写的同时提供了一些Scala 特性,它是一个生成为目的的构建工具。

为什么选择SBT?

启程

java -Xmx521M -jar sbt-launch.jar "$@"

cal ~/projects]$ sbt
Project does not exist, create new project? (y/N/s) y
Name: sample
Organization: com.twitter
Version [1.0]: 1.0-SNAPSHOT
Scala version [2.7.7]: 2.8.1
sbt version [0.7.4]:      
Getting Scala 2.7.7 ...
:: retrieving :: org.scala-tools.sbt#boot-scala
	confs: [default]
	2 artifacts copied, 0 already retrieved (9911kB/221ms)
Getting org.scala-tools.sbt sbt_2.7.7 0.7.4 ...
:: retrieving :: org.scala-tools.sbt#boot-app
	confs: [default]
	15 artifacts copied, 0 already retrieved (4096kB/167ms)
[success] Successfully initialized directory structure.
Getting Scala 2.8.1 ...
:: retrieving :: org.scala-tools.sbt#boot-scala
	confs: [default]
	2 artifacts copied, 0 already retrieved (15118kB/386ms)
[info] Building project sample 1.0-SNAPSHOT against Scala 2.8.1
[info]    using sbt.DefaultProject with sbt 0.7.4 and Scala 2.7.7
> 

注意项目以SNAPSHOT 版本开始是一个不错的惯例。

项目轮廓

添加代码

我们将为简单的tweets 创建一个简单的JSON 解析器。把下面代码添加到/src/main/scala/com/twitter/sample/SimpleParser.scala

package com.twitter.sample

case class SimpleParsed(id: Long, text: String)

class SimpleParser {

  val tweetRegex = "\"id\":(.*),\"text\":\"(.*)\"".r

  def parse(str: String) = {
    tweetRegex.findFirstMatchIn(str) match {
      case Some(m) => {
        val id = str.substring(m.start(1), m.end(1)).toInt
        val text = str.substring(m.start(2), m.end(2))
        Some(SimpleParsed(id, text))
      }
      case _ => None
    }
  }
}

这代码很丑陋有很多bug,不过还好可以编译。

在控制台里面测试

SBT 可以被当做一个命令行脚本或者一个构建控制台。我们将主要把它当做构建控制台,但是更多的命令可以作为SBT 的一个参数传入命令单独运行,比如

sbt test

注意如果命令接受参数,你需要给整个参数路径加引号,比如

sbt 'test-only com.twitter.sample.SampleSpec'

方式很奇怪。

不管怎样,用我们的代码来运行,启动sbt

[local ~/projects/sbt-sample]$ sbt
[info] Building project sample 1.0-SNAPSHOT against Scala 2.8.1
[info]    using sbt.DefaultProject with sbt 0.7.4 and Scala 2.7.7
> 

SBT 允许你在所有的工程依赖里加载一个Scala REPL。它在运行控制台之前编译你的项目源文件,给我们提供一个快速的解析方法。

> console
[info] 
[info] == compile ==
[info]   Source analysis: 0 new/modified, 0 indirectly invalidated, 0 removed.
[info] Compiling main sources...
[info] Nothing to compile.
[info]   Post-analysis: 3 classes.
[info] == compile ==
[info] 
[info] == copy-test-resources ==
[info] == copy-test-resources ==
[info] 
[info] == test-compile ==
[info]   Source analysis: 0 new/modified, 0 indirectly invalidated, 0 removed.
[info] Compiling test sources...
[info] Nothing to compile.
[info]   Post-analysis: 0 classes.
[info] == test-compile ==
[info] 
[info] == copy-resources ==
[info] == copy-resources ==
[info] 
[info] == console ==
[info] Starting scala interpreter...
[info] 
Welcome to Scala version 2.8.1.final (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_22).
Type in expressions to have them evaluated.
Type :help for more information.

scala> 

我们的代码编译后,我们可以输入Scala 命令。我们会创建一个新的解析器,一个复制的tweet,一个明确的”任务“。

scala> import com.twitter.sample._            
import com.twitter.sample._

scala> val tweet = """{"id":1,"text":"foo"}"""
tweet: java.lang.String = {"id":1,"text":"foo"}

scala> val parser = new SimpleParser          
parser: com.twitter.sample.SimpleParser = com.twitter.sample.SimpleParser@71060c3e

scala> parser.parse(tweet)                    
res0: Option[com.twitter.sample.SimpleParsed] = Some(SimpleParsed(1,"foo"}))

scala> 

增加依赖

我们针对这个很小集合输入的简单解析工作了,但是我们想要打断它插入一个测试。第一步是添加specs 测试类库以及给我们的项目添加一个真正的JSON 解析。为了做到这点,我们不得不在默认SBT 轮廓之外创建一个项目。

SBT 把project/build 路径下的Scala 文件当做项目定义。把下面的代码添加到project/build/SampleProject.scala。

mport sbt._

class SampleProject(info: ProjectInfo) extends DefaultProject(info) {
  val jackson = "org.codehaus.jackson" % "jackson-core-asl" % "1.6.1"
  val specs = "org.scala-tools.testing" % "specs_2.8.0" % "1.6.5" % "test"
}

一个项目的定义是一个SBT class。在这里我们扩展了SBT DefaultProject。

你通过val 声明一个依赖。SBT 使用反射来扫描你项目里的所有的依赖vals 然后在构建时创建一个依赖树。语法看起来可能有些陌生,但是它和maven 以来差不多。

<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-core-asl</artifactId>
    <version>1.6.1</version>
</dependency>
<dependency>
    <groupId>org.scala-tools.testing</groupId>
    <artifactId>specs_2.8.0</artifactId>
    <version>1.6.5</version>
    <scope>test</scope>
</dependency>

现在我可以给我们的工程下载依赖了。从命令行(不是sbt 控制台),运行sbt update

[local ~/projects/sbt-sample]$ sbt update
[info] Building project sample 1.0-SNAPSHOT against Scala 2.8.1
[info]    using SampleProject with sbt 0.7.4 and Scala 2.7.7
[info] 
[info] == update ==
[info] :: retrieving :: com.twitter#sample_2.8.1 [sync]
[info] 	confs: [compile, runtime, test, provided, system, optional, sources, javadoc]
[info] 	1 artifacts copied, 0 already retrieved (2785kB/71ms)
[info] == update ==
[success] Successful.
[info] 
[info] Total time: 1 s, completed Nov 24, 2010 8:47:26 AM
[info] 
[info] Total session time: 2 s, completed Nov 24, 2010 8:47:26 AM
[success] Build completed successfully.

你会看到sbt 检索specs 库。你现在将要拥有一个lib_managed 库,同时lib_managed/scala_2.8.1/test 将有specs_2.8.0-1.6.5.jar

添加测试

现在我们添加了测试类库,把下面的代码放到 src/test/scala/com/twitter/sample/SimpleParserSpec.scala

package com.twitter.sample

import org.specs._

object SimpleParserSpec extends Specification {
  "SimpleParser" should {
    val parser = new SimpleParser()
    "work with basic tweet" in {
      val tweet = """{"id":1,"text":"foo"}"""
      parser.parse(tweet) match {
        case Some(parsed) => {
          parsed.text must be_==("foo")
          parsed.id must be_==(1)
        }
        case _ => fail("didn't parse tweet")
      }
    }
  }
}

在sbt 控制台里,运行测试

> test
[info] 
[info] == compile ==
[info]   Source analysis: 0 new/modified, 0 indirectly invalidated, 0 removed.
[info] Compiling main sources...
[info] Nothing to compile.
[info]   Post-analysis: 3 classes.
[info] == compile ==
[info] 
[info] == test-compile ==
[info]   Source analysis: 0 new/modified, 0 indirectly invalidated, 0 removed.
[info] Compiling test sources...
[info] Nothing to compile.
[info]   Post-analysis: 10 classes.
[info] == test-compile ==
[info] 
[info] == copy-test-resources ==
[info] == copy-test-resources ==
[info] 
[info] == copy-resources ==
[info] == copy-resources ==
[info] 
[info] == test-start ==
[info] == test-start ==
[info] 
[info] == com.twitter.sample.SimpleParserSpec ==
[info] SimpleParserSpec
[info] SimpleParser should
[info]   + work with basic tweet
[info] == com.twitter.sample.SimpleParserSpec ==
[info] 
[info] == test-complete ==
[info] == test-complete ==
[info] 
[info] == test-finish ==
[info] Passed: : Total 1, Failed 0, Errors 0, Passed 1, Skipped 0
[info]  
[info] All tests PASSED.
[info] == test-finish ==
[info] 
[info] == test-cleanup ==
[info] == test-cleanup ==
[info] 
[info] == test ==
[info] == test ==
[success] Successful.
[info] 
[info] Total time: 0 s, completed Nov 24, 2010 8:54:45 AM
> 

我们的测试工作了!现在我们来添加更多。SBT 提供的更好的方式是运行触发行为。Prefacing 一个含有tilde 的动作会开始一个循环,它会在源文件改变时运行。让我们运行run~test 看看会发生什么。

[info] == test ==
[success] Successful.
[info] 
[info] Total time: 0 s, completed Nov 24, 2010 8:55:50 AM
1. Waiting for source changes... (press enter to interrupt)

现在让我们来添加下面的测试用例

"reject a non-JSON tweet" in {
      val tweet = """"id":1,"text":"foo""""
      parser.parse(tweet) match {
        case Some(parsed) => fail("didn't reject a non-JSON tweet")
        case e => e must be_==(None)
      }
    }

    "ignore nested content" in {
      val tweet = """{"id":1,"text":"foo","nested":{"id":2}}"""
      parser.parse(tweet) match {
        case Some(parsed) => {
          parsed.text must be_==("foo")
          parsed.id must be_==(1)
        }
        case _ => fail("didn't parse tweet")
      }
    }

    "fail on partial content" in {
      val tweet = """{"id":1}"""
      parser.parse(tweet) match {
        case Some(parsed) => fail("didn't reject a partial tweet")
        case e => e must be_==(None)
      }
    }

当我们保存文件的时候,SBT 检测到改变,运行测试,然后通知我们我们的解析是lame

[info] == com.twitter.sample.SimpleParserSpec ==
[info] SimpleParserSpec
[info] SimpleParser should
[info]   + work with basic tweet
[info]   x reject a non-JSON tweet
[info]     didn't reject a non-JSON tweet (Specification.scala:43)
[info]   x ignore nested content
[info]     'foo","nested":{"id' is not equal to 'foo' (SimpleParserSpec.scala:31)
[info]   + fail on partial content

现在让我们重新开始我们更真实的的JSON 解析

package com.twitter.sample

import org.codehaus.jackson._
import org.codehaus.jackson.JsonToken._

case class SimpleParsed(id: Long, text: String)

class SimpleParser {

  val parserFactory = new JsonFactory()

  def parse(str: String) = {
    val parser = parserFactory.createJsonParser(str)
    if (parser.nextToken() == START_OBJECT) {
      var token = parser.nextToken()
      var textOpt:Option[String] = None
      var idOpt:Option[Long] = None
      while(token != null) {
        if (token == FIELD_NAME) {
          parser.getCurrentName() match {
            case "text" => {
              parser.nextToken()
              textOpt = Some(parser.getText())
            }
            case "id" => {
              parser.nextToken()
              idOpt = Some(parser.getLongValue())
            }
            case _ => // noop
          }
        }
        token = parser.nextToken()
      }
      if (textOpt.isDefined && idOpt.isDefined) {
        Some(SimpleParsed(idOpt.get, textOpt.get))
      } else {
        None
      }
    } else {
      None
    }
  }
}

这是一个简单的Jackson 解析。当我们保存的时候,SBT 重新编译我们的代码然后重新运行测试。让它更好!

info] SimpleParser should
[info]   + work with basic tweet
[info]   + reject a non-JSON tweet
[info]   x ignore nested content
[info]     '2' is not equal to '1' (SimpleParserSpec.scala:32)
[info]   + fail on partial content
[info] == com.twitter.sample.SimpleParserSpec ==

恩,我们需要检查伴生类。让我们添加一些丑陋的guard 来给我们的reading loop。

def parse(str: String) = {
    val parser = parserFactory.createJsonParser(str)
    var nested = 0
    if (parser.nextToken() == START_OBJECT) {
      var token = parser.nextToken()
      var textOpt:Option[String] = None
      var idOpt:Option[Long] = None
      while(token != null) {
        if (token == FIELD_NAME && nested == 0) {
          parser.getCurrentName() match {
            case "text" => {
              parser.nextToken()
              textOpt = Some(parser.getText())
            }
            case "id" => {
              parser.nextToken()
              idOpt = Some(parser.getLongValue())
            }
            case _ => // noop
          }
        } else if (token == START_OBJECT) {
          nested += 1
        } else if (token == END_OBJECT) {
          nested -= 1
        }
        token = parser.nextToken()
      }
      if (textOpt.isDefined && idOpt.isDefined) {
        Some(SimpleParsed(idOpt.get, textOpt.get))
      } else {
        None
      }
    } else {
      None
    }
  }

它生效了!

打包和部署

在这里我们可以运行package 命令来生成jar 文件。不管怎样,我们可能想要和我们的团队共享我们的jar 文件。为了做到这一点我们将要构建与标准工程,这将会给我们一个大的头部开始。

第一步就是在SBT plugin 里面包含StandardProject 。插件是给你的构建引入依赖的一种方式,和你的project 一样。这些依赖定义在project/plugins/Plugins.scala 里。把下面的代码添加到你的Plugins.scala 文件里。

import sbt._

class Plugins(info: ProjectInfo) extends PluginDefinition(info) {
  val twitterMaven = "twitter.com" at "http://maven.twttr.com/"
  val defaultProject = "com.twitter" % "standard-project" % "0.7.14"
}

注意我们指定了一个maven 开发库做为依赖。这是因为标准的工程类库是被我们托管的,它不是默认检查的sbt 开发库。

我们也个呢更新我们的project 定义来扩展StandardProject,包括SVN 发布trait,以及定义开发库做为希望发布的那样。把SampleProject.scala 按如下修改

mport sbt._
import com.twitter.sbt._

class SampleProject(info: ProjectInfo) extends StandardProject(info) with SubversionPublisher {
  val jackson = "org.codehaus.jackson" % "jackson-core-asl" % "1.6.1"
  val specs = "org.scala-tools.testing" % "specs_2.8.0" % "1.6.5" % "test"

  override def subversionRepository = Some("http://svn.local.twitter.com/maven/")
}

现在如果我们运行publish 命令我们会看到如下

[info] == deliver ==
IvySvn Build-Version: null
IvySvn Build-DateTime: null
[info] :: delivering :: com.twitter#sample;1.0-SNAPSHOT :: 1.0-SNAPSHOT :: release :: Wed Nov 24 10:26:45 PST 2010
[info] 	delivering ivy file to /Users/mmcbride/projects/sbt-sample/target/ivy-1.0-SNAPSHOT.xml
[info] == deliver ==
[info] 
[info] == make-pom ==
[info] Wrote /Users/mmcbride/projects/sbt-sample/target/sample-1.0-SNAPSHOT.pom
[info] == make-pom ==
[info] 
[info] == publish ==
[info] :: publishing :: com.twitter#sample
[info] Scheduling publish to http://svn.local.twitter.com/maven/com/twitter/sample/1.0-SNAPSHOT/sample-1.0-SNAPSHOT.jar
[info] 	published sample to com/twitter/sample/1.0-SNAPSHOT/sample-1.0-SNAPSHOT.jar
[info] Scheduling publish to http://svn.local.twitter.com/maven/com/twitter/sample/1.0-SNAPSHOT/sample-1.0-SNAPSHOT.pom
[info] 	published sample to com/twitter/sample/1.0-SNAPSHOT/sample-1.0-SNAPSHOT.pom
[info] Scheduling publish to http://svn.local.twitter.com/maven/com/twitter/sample/1.0-SNAPSHOT/ivy-1.0-SNAPSHOT.xml
[info] 	published ivy to com/twitter/sample/1.0-SNAPSHOT/ivy-1.0-SNAPSHOT.xml
[info] Binary diff deleting com/twitter/sample/1.0-SNAPSHOT
[info] Commit finished r977 by 'mmcbride' at Wed Nov 24 10:26:47 PST 2010
[info] Copying from com/twitter/sample/.upload to com/twitter/sample/1.0-SNAPSHOT
[info] Binary diff finished : r978 by 'mmcbride' at Wed Nov 24 10:26:47 PST 2010
[info] == publish ==
[success] Successful.
[info] 
[info] Total time: 4 s, completed Nov 24, 2010 10:26:47 AM

过一会儿以后,我们可以到binaries.local.twitter.com:http://binaries.local.twitter/maven/com/twitter/sample/1.0-SNAPSHOT/ 来找到publish.jar。

添加任务

任务就是Scala 函数,添加任务的最简单方法就是在工程定义里面用task 方法来include 一个val,比如。

lazy val print = task {log.info("a test action"); None}

如果你想要添加依赖和描述你可以向这样

lazy val print = task {log.info("a test action"); None}.dependsOn(compile) describedAs("prints a line after compile")

如果你重新加载我们的工程并且运行print 命令,你会看到如下

> print
[info] 
[info] == print ==
[info] a test action
[info] == print ==
[success] Successful.
[info] 
[info] Total time: 0 s, completed Nov 24, 2010 11:05:12 AM
> 

因此,它工作了,如果你在单个项目里定义一个任务,这个任务还好。无论如何,如果你把它定义在一个插件里会相当的代办。我会这么办

lazy val print = printAction
def printAction = printTask.dependsOn(compile) describedAs("prints a line after compile")
def printTask = task {log.info("a test action"); None}

它允许消费者重载任务本身,任务的依赖和/或描述,或者是动作。更多的SBT 构建行为遵循这个模式。做为例子,我们修改了builtin 包task,来打印当前处理的时间戳。

lazy val printTimestamp = task { log.info("current time is " + System.currentTimeMillis); None}
override def packageAction = super.packageAction.dependsOn(printTimestamp)

StandardProject 有一些调整默认SBT 和订制任务的例子。

快速参考

一般命令

Moar 命令

项目轮廓

TBD