由於Scala有一個比較完備的Eclipse IDE（Scala IDE for Eclipse）, 對於不想從eclipse遷移到Iea平臺的Dev來說，如何方便、快速、有效得在Eclipse下編譯打包開發Scala應用程式尤為重要。Sbt是類似Maven的一個構建工具，我們將使用它來構建釋出程式。

    本文會介紹搭建Eclipse開發Scala應用程式的一般步驟，並結合例項演示sbt工具在eclipse裡是如何建立專案檔案，和編譯打包部署程式的。

    這裡做個備忘，也為初學者少走彎路而做出點小小的貢獻。

  一、環境準備：

   以上列出均為開發時必須的軟體環境：

   我的，Scala版本是2.10.3， Sbt版本是0.13

  二、sbt生成scala eclipse專案：

     我們想要在Eclipse裡開發scala應用並符合sbt釋出程式的檔案結構（類似Maven結構），除了手工建立檔案結構，還可以採用sbt eclipse的配置方法。

    2.1、新增sbt eclipse外掛

     有2種配置方式：

     一種是在~/.sbt/0.13/plugins//build.sbt 裡配置addPlugin,這種做法是全域性的外掛，即對本機所有sbt專案均使用。

    另一種是每個專案不一樣的plugins，則是在每個專案跟目錄下project/plugins.sbt裡進行外掛配置。

    比如test_sbt：

[email protected]:~/workspace/test_sbt$ pwd
/home/victor/workspace/test_sbt

victor-ubuntu:~/workspace/test_sbt$ tree .
.
├── build.sbt
└── project
    └── plugins.sbt

1 directory, 2 files

    plugins.sbt裡面內容配置，新增外掛：

addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.4.0")
  
 

   2.2、生成eclipse專案檔案

   然後進入到根目錄sbt,成功進入sbt，執行eclipse命令生成eclipse的.classpath等eclipse相關檔案：

[email protected]:~/workspace/test_sbt$ ll
total 28
drwxrwxr-x 5 victor victor 4096  8月  4 00:38 ./
drwxrwxr-x 8 victor victor 4096  8月  4 00:28 ../
-rw-rw-r-- 1 victor victor    0  8月  4 00:38 build.sbt
-rw-rw-r-- 1 victor victor  589  8月  4 00:38 .classpath
drwxrwxr-x 4 victor victor 4096  8月  4 00:38 project/
-rw-rw-r-- 1 victor victor  362  8月  4 00:38 .project
drwxrwxr-x 4 victor victor 4096  8月  4 00:38 src/
drwxrwxr-x 4 victor victor 4096  8月  4 00:38 target/

  可以看到和maven的目錄結構是相似的：

[email protected]:~/workspace/test_sbt$ tree src
src
├── main
│   ├── java
│   └── scala
└── test
    ├── java
    └── scala

  發現沒有resouces目錄：

  在跟目錄的build.sbt裡新增：

EclipseKeys.createSrc := EclipseCreateSrc.Default + EclipseCreateSrc.Resource

   再執行sbt eclipse 

[email protected]:~/workspace/test_sbt$ tree src/
src/
├── main
│   ├── java
│   ├── resources
│   └── scala
└── test
    ├── java
    ├── resources
    └── scala

   2.3、匯入Eclipse中

   我們進入Eclipse，利用匯入嚮導的import existing project into workspace這一項進行匯入。

  

    至此，我們的專案結構搭建完成，可以像開發java maven專案一樣的開發scala sbt專案了。

   三、開發與部署

    下面準備用一個實際例子演示在Scala裡開發的一般步驟，最近用到scala裡的json，就用json4s這個json lib來開發一個解析json的例子，json4s地址：https://github.com/json4s/json4s

    3.1、新增依賴

     我們如果想使用第三方的類，就需要新增依賴關係，和GAV座標，這個再熟悉不過，我們需要編輯根目錄下的build.sbt檔案，新增依賴：

     這裡name,version,scalaVersion要注意每個間隔一行，其它的也是，不然會出錯。

     libraryDependencies是新增依賴的地方：我們新增2個。

    resolvers是倉庫地址，這裡配置了多個。

   如下：

name := "shengli_test_sbt"

version := "1.0"

scalaVersion := "2.10.3"

EclipseKeys.createSrc := EclipseCreateSrc.Default + EclipseCreateSrc.Resource

libraryDependencies ++= Seq(
  "org.json4s" %% "json4s-native" % "3.2.10",
  "org.json4s" %% "json4s-jackson" % "3.2.10"
)

resolvers ++= Seq(
      // HTTPS is unavailable for Maven Central
      "Maven Repository"     at "http://repo.maven.apache.org/maven2",
      "Apache Repository"    at "https://repository.apache.org/content/repositories/releases",
      "JBoss Repository"     at "https://repository.jboss.org/nexus/content/repositories/releases/",
      "MQTT Repository"      at "https://repo.eclipse.org/content/repositories/paho-releases/",
      "Cloudera Repository"  at "http://repository.cloudera.com/artifactory/cloudera-repos/",
      // For Sonatype publishing
      // "sonatype-snapshots"   at "https://oss.sonatype.org/content/repositories/snapshots",
      // "sonatype-staging"     at "https://oss.sonatype.org/service/local/staging/deploy/maven2/",
      // also check the local Maven repository ~/.m2
      Resolver.mavenLocal
)

    再次執行sbt eclipse，則依賴的jar包會自動載入到classpath：

      

    3.2、測試程式

    一個簡單的解析Json的程式，程式很簡單，這裡就不解釋了。

package com.shengli.json
import org.json4s._
import org.json4s.JsonDSL._
import org.json4s.jackson.JsonMethods._

object JsonSbtTest extends Application{
	

  case class Winner(id: Long, numbers: List[Int])
  case class Lotto(id: Long, winningNumbers: List[Int], winners: List[Winner], drawDate: Option[java.util.Date])

  val winners = List(Winner(23, List(2, 45, 34, 23, 3, 5)), Winner(54, List(52, 3, 12, 11, 18, 22)))
  val lotto = Lotto(5, List(2, 45, 34, 23, 7, 5, 3), winners, None)
  val json =
    ("lotto" ->
      ("lotto-id" -> lotto.id) ~ 
      ("winning-numbers" -> lotto.winningNumbers) ~
      ("draw-date" -> lotto.drawDate.map(_.toString)) ~
      ("winners" ->
        lotto.winners.map { w =>
          (("winner-id" -> w.id) ~
           ("numbers" -> w.numbers))}))

  println(compact(render(json)))
  println(pretty(render(json)))
}

    至此我們在eclipse能執行Run as Scala Application，但是如何加依賴打包釋出呢？

    3.3、Assembly

   還記得Spark裡面的assembly嗎？那個就是釋出用的，sbt本身支援的clean compile package之類的命令，但是帶依賴的one jar打包方式還是assembly比較成熟。

clean	Deletes all generated files (in the target directory).
compile	Compiles the main sources (in src/main/scala and src/main/java directories).
test	Compiles and runs all tests.
console	Starts the Scala interpreter with a classpath including the compiled sources and all dependencies. To return to sbt, type:quit, Ctrl+D (Unix), or Ctrl+Z (Windows).
run <argument>*	Runs the main class for the project in the same virtual machine as sbt.
package	Creates a jar file containing the files in src/main/resources and the classes compiled fromsrc/main/scala andsrc/main/java.
help <command>	Displays detailed help for the specified command. If no command is provided, displays brief descriptions of all commands.
reload	Reloads the build definition (build.sbt, project/*.scala, project/*.sbt files). Needed if you change the build definition.

   Assembly：

   Assembly是作為一種外掛的，所以要在project下面的plugins.sbt裡面配置，至此plugins.sbt檔案裡內容如下：

resolvers += Resolver.url("artifactory", url("http://scalasbt.artifactoryonline.com/scalasbt/sbt-plugin-releases"))(Resolver.ivyStylePatterns)

resolvers += "Typesafe Repository" at "http://repo.typesafe.com/typesafe/releases/"

addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.4.0")

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.11.2")

    除了外掛的配置之外，還需要配置跟目錄下build.sbt，支援assembly，在檔案頭部加入：

import AssemblyKeys._
assemblySettings

   至此build.sbt檔案內容如下：

import AssemblyKeys._
assemblySettings

name := "shengli_test_sbt"

version := "1.0"

scalaVersion := "2.10.3"

EclipseKeys.createSrc := EclipseCreateSrc.Default + EclipseCreateSrc.Resource

libraryDependencies ++= Seq(
  "org.json4s" %% "json4s-native" % "3.2.10",
  "org.json4s" %% "json4s-jackson" % "3.2.10"
)

resolvers ++= Seq(
      // HTTPS is unavailable for Maven Central
      "Maven Repository"     at "http://repo.maven.apache.org/maven2",
      "Apache Repository"    at "https://repository.apache.org/content/repositories/releases",
      "JBoss Repository"     at "https://repository.jboss.org/nexus/content/repositories/releases/",
      "MQTT Repository"      at "https://repo.eclipse.org/content/repositories/paho-releases/",
      "Cloudera Repository"  at "http://repository.cloudera.com/artifactory/cloudera-repos/",
      // For Sonatype publishing
      // "sonatype-snapshots"   at "https://oss.sonatype.org/content/repositories/snapshots",
      // "sonatype-staging"     at "https://oss.sonatype.org/service/local/staging/deploy/maven2/",
      // also check the local Maven repository ~/.m2
      Resolver.mavenLocal
)

   執行sbt assembly命令進行釋出：

> assembly
[info] Updating {file:/home/victor/workspace/test_sbt/}test_sbt...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] Compiling 1 Scala source to /home/victor/workspace/test_sbt/target/scala-2.10/classes...
[warn] there were 1 deprecation warning(s); re-run with -deprecation for details
[warn] one warning found
[info] Including: scala-compiler-2.10.0.jar
[info] Including: scala-library-2.10.3.jar
[info] Including: json4s-native_2.10-3.2.10.jar
[info] Including: json4s-core_2.10-3.2.10.jar
[info] Including: json4s-ast_2.10-3.2.10.jar
[info] Including: paranamer-2.6.jar
[info] Including: scalap-2.10.0.jar
[info] Including: jackson-databind-2.3.1.jar
[info] Including: scala-reflect-2.10.0.jar
[info] Including: jackson-annotations-2.3.0.jar
[info] Including: json4s-jackson_2.10-3.2.10.jar
[info] Including: jackson-core-2.3.1.jar
[info] Checking every *.class/*.jar file's SHA-1.
[info] Merging files...
[warn] Merging 'META-INF/NOTICE' with strategy 'rename'
[warn] Merging 'META-INF/LICENSE' with strategy 'rename'
[warn] Merging 'META-INF/MANIFEST.MF' with strategy 'discard'
[warn] Merging 'rootdoc.txt' with strategy 'concat'
[warn] Strategy 'concat' was applied to a file
[warn] Strategy 'discard' was applied to a file
[warn] Strategy 'rename' was applied to 2 files
[info] SHA-1: d4e76d7b55548fb2a6819f2b94e37daea9421684
[info] Packaging /home/victor/workspace/test_sbt/target/scala-2.10/shengli_test_sbt-assembly-1.0.jar ...
[info] Done packaging.
[success] Total time: 39 s, completed Aug 4, 2014 1:26:11 AM

  我們發現檔案釋出到了/home/victor/workspace/test_sbt/target/scala-2.10/shengli_test_sbt-assembly-1.0.jar

  那我們來執行一下，看是否成功：

  執行：

java -cp /home/victor/workspace/test_sbt/target/scala-2.10/shengli_test_sbt-assembly-1.0.jar com.shengli.json.JsonSbtTest

[email protected]:~/workspace/test_sbt$ java -cp /home/victor/workspace/test_sbt/target/scala-2.10/shengli_test_sbt-assembly-1.0.jar com.shengli.json.JsonSbtTest
{"lotto":{"lotto-id":5,"winning-numbers":[2,45,34,23,7,5,3],"winners":[{"winner-id":23,"numbers":[2,45,34,23,3,5]},{"winner-id":54,"numbers":[52,3,12,11,18,22]}]}}
{
  "lotto" : {
    "lotto-id" : 5,
    "winning-numbers" : [ 2, 45, 34, 23, 7, 5, 3 ],
    "winners" : [ {
      "winner-id" : 23,
      "numbers" : [ 2, 45, 34, 23, 3, 5 ]
    }, {
      "winner-id" : 54,
      "numbers" : [ 52, 3, 12, 11, 18, 22 ]
    } ]
  }
}

   證實發布的結果是成功的。

四、總結

   本文介紹了在Eclipse裡利用Sbt構建開發Scala程式的一般步驟，並用例項講解了整個流程。

   用sbt eclipse外掛生成sbt檔案目錄結構，sbt eclipse命令來生成更新jar包依賴。

   用assebly外掛對scala應用進行打包釋出。  

——EOF——