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關(guān)于SBT
SBT是一個現(xiàn)代化的構(gòu)建工具。雖然它由Scala編寫并提供了很多Scala便利，但它是一個通用的構(gòu)建工具。
為什么選擇SBT？
明智的依賴管理
使用Ivy做依賴管理
“只在請求時更新”的模型
對創(chuàng)建任務(wù)全面的Scala語言支持
連續(xù)執(zhí)行命令
在項目上下文內(nèi)啟動解釋器
入門
譯注 最新的SBT安裝方式請參考 scala-sbt的文檔
下載jar包 地址
創(chuàng)建一個調(diào)用這個jar的SBT shell腳本，例如
java -Xmx512M -jar sbt-launch.jar "$@"
確保它是可執(zhí)行的，并在你的path下
運行sbt來創(chuàng)建項目
[local ~/projects]$ 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 >
可以看到它已經(jīng)以較好的形式創(chuàng)建了項目的快照版本。
項目布局
項目 – 項目定義文件
project/build/
project/build.properties – 項目、sbt和Scala版本定義
src/main – 你的應(yīng)用程序代碼出現(xiàn)在這里，在子目錄表明代碼的語言（如src/main/scala, src/main/java）
src/main/resources – 你想要添加到j(luò)ar包中的靜態(tài)文件（如日志配置）
src/test – 就像src/main，不過是對測試
lib_managed – 你的項目依賴的jar文件。由sbt update時填充
target – 生成物的目標(biāo)路徑（如自動生成的thrift代碼，類文件，jar包）
添加一些代碼
我們將為簡單的tweet消息創(chuàng)建一個簡單的JSON解析器。將以下代碼加在這個文件中
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
}
}
}這段代碼丑陋并有bug，但應(yīng)該能夠編譯通過。
在控制臺中的測試
SBT既可以用作命令行腳本，也可以作為構(gòu)建控制臺。我們將主要利用它作為構(gòu)建控制臺，不過大多數(shù)命令可以作為參數(shù)傳遞給SBT獨立運行，如
sbt test
需要注意如果一個命令需要參數(shù)，你需要使用引號包括住整個參數(shù)路徑，例如
sbt 'test-only com.twitter.sample.SampleSpec'
這種方式很奇怪。
不管怎樣，要開始我們的代碼工作了，啟動SBT吧
[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允許你啟動一個Scala REPL并加載所有項目依賴。它會在啟動控制臺前編譯項目的源代碼，從而為我們提供一個快速測試解析器的工作臺。
> 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>
我們代碼編譯通過了，并提供了典型的Scala提示符。我們將創(chuàng)建一個新的解析器，一個tweet以確保其“能工作”
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>添加依賴
我們簡單的解析器對這個非常小的輸入集工作正常，但我們需要添加更多的測試并讓它出錯。第一步是在我們的項目中添加specs測試庫和一個真正的JSON解析器。要做到這一點，我們必須超越默認(rèn)的SBT項目布局來創(chuàng)建一個項目。
SBT認(rèn)為project/build目錄中的Scala文件是項目定義。添加以下內(nèi)容到這個文件中project/build/SampleProject.scala
import 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"
}一個項目定義是一個SBT類。在上面例子中，我們擴展了SBT的DefaultProject。
這里是通過val聲明依賴。SBT使用反射來掃描項目中的所有val依賴，并在構(gòu)建時建立依賴關(guān)系樹。這里使用的語法可能是新的，但本質(zhì)和Maven依賴是相同的
<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>
現(xiàn)在可以下載我們的項目依賴了。在命令行中（而不是sbt console中）運行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.
你會看到sbt檢索到specs庫。現(xiàn)在還增加了一個lib_managed目錄，并且在lib_managed/scala_2.8.1/test目錄中包含 specs_2.8.0-1.6.5.jar
添加測試
現(xiàn)在有了測試庫，可以把下面的測試代碼寫入src/test/scala/com/twitter/sample/SimpleParserSpec.scala文件
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控制臺中運行test
> 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 >
我們的測試通過了！現(xiàn)在，我們可以增加更多。運行觸發(fā)動作是SBT提供的優(yōu)秀特性之一。在動作開始添加一個波浪線會啟動一個循環(huán)，在源文件發(fā)生變化時重新運行動作。讓我們運行 ~test 并看看會發(fā)生什么吧。
[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)
現(xiàn)在，讓我們添加下面的測試案例
"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)
}
}在我們保存文件后，SBT會檢測到變化，運行測試，并通知我們的解析器有問題
[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因此，讓我們返工實現(xiàn)真正的JSON解析器
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
}
}
}這是一個簡單的Jackson解析器。當(dāng)我們保存，SBT會重新編譯代碼和運行測試。代碼變得越來越好了！
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 ==
哦。我們需要檢查嵌套對象。讓我們在token讀取循環(huán)處添加一些丑陋的守衛(wèi)。
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
}
}…測試通過了！
打包和發(fā)布
現(xiàn)在我們已經(jīng)可以運行package命令來生成一個jar文件。不過我們可能要與其他組分享我們的jar包。要做到這一點，我們將在StandardProject基礎(chǔ)上構(gòu)建，這給了我們一個良好的開端。
第一步是引入StandardProject為SBT插件。插件是一種為你的構(gòu)建引進依賴的方式，注意不是為你的項目引入。這些依賴關(guān)系定義在project/plugins/Plugins.scala文件中。添加以下代碼到Plugins.scala文件中。
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"
}注意我們指定了一個Maven倉庫和一個依賴。這是因為這個標(biāo)準(zhǔn)項目庫是由twitter托管的，不在SBT默認(rèn)檢查的倉庫中。
我們也將更新項目定義來擴展StandardProject，包括SVN發(fā)布特質(zhì)，和我們希望發(fā)布的倉庫定義。修改SampleProject.scala
import 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/")
}現(xiàn)在如果我們運行發(fā)布操作，將看到以下輸出
[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
這樣（一段時間后），就可以在 binaries.local.twitter.com 上看到我們發(fā)布的jar包。
添加任務(wù)
任務(wù)就是Scala函數(shù)。添加一個任務(wù)最簡單的方法是，在你的項目定義中引入一個val定義的任務(wù)方法，如
lazy val print = task {log.info("a test action"); None}你也可以這樣加上依賴和描述
lazy val print = task {log.info("a test action"); None}.dependsOn(compile) describedAs("prints a line after compile")刷新項目，并執(zhí)行print操作，我們將看到以下輸出
> 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 >
所以它起作用了。如果你只是在一個項目定義一個任務(wù)的話，這工作得很好。然而如果你定義的是一個插件的話，它就很不靈活了。我可能要
lazy val print = printAction
def printAction = printTask.dependsOn(compile) describedAs("prints a line after compile")
def printTask = task {log.info("a test action"); None}這可以讓消費者覆蓋任務(wù)本身，依賴和/或任務(wù)的描述，或動作本身。大多數(shù)SBT內(nèi)建的動作都遵循這種模式。作為一個例子，我們可以通過修改內(nèi)置打包任務(wù)來打印當(dāng)前時間戳
lazy val printTimestamp = task { log.info("current time is " + System.currentTimeMillis); None}
override def packageAction = super.packageAction.dependsOn(printTimestamp)有很多例子介紹了怎樣調(diào)整SBT默認(rèn)的StandardProject，和如何添加自定義任務(wù)。
快速參考
常用命令
actions – 顯示這個項目中可用的動作
update – 下載依賴
compile – 編譯源文件
test – 運行測試
package – 創(chuàng)建一個可發(fā)布的jar文件
publish-local – 在本地ivy緩存中安裝構(gòu)建好的jar包
publish – 將你的jar推到一個遠程庫中（如果配置了的話）
更多命令
test-failed – 運行所有失敗的規(guī)格測試
test-quick – 運行任何失敗的和/或依賴更新的規(guī)格
clean-cache – 刪除SBT緩存各種的東西。就像sbt的clean命令
clean-lib – 刪除lib_managed下的一切
項目布局
待續(xù)