scala eclipse sbt 应用程序开发

由于Scala有一个比较完备的Eclipse IDE（Scala IDE for Eclipse）, 对于不想从eclipse迁移到Iea平台的Dev来说，如何方便、快速、有效得在Eclipse下编译打包开发Scala应用程序尤为重要。Sbt是类似Maven的一个构建工具，我们将使用它来构建发布程序。

本文会介绍搭建Eclipse开发Scala应用程序的一般步骤，并结合实例演示sbt工具在eclipse里是如何创建项目文件，和编译打包部署程序的。

这里做个备忘，也为初学者少走弯路而做出点小小的贡献。

一、环境准备：

1、Scala : http://www.scala-lang.org/

2、Scala IDE for Eclipse :scala-ide.org

3、Sbt: http://www.scala-sbt.org/

4、Sbt Eclipse : https://github.com/typesafehub/sbteclipse   typesafe的一个sbt for eclipse的助手，可以帮助生成eclipse

5、Sbt Assembly ： https://github.com/sbt/sbt-assembly 发布应用程序的一个sbt插件。

以上列出均为开发时必须的软件环境：

我的，Scala版本是2.10.3， Sbt版本是0.13

二、sbt生成scala eclipse项目：

我们想要在Eclipse里开发scala应用并符合sbt发布程序的文件结构（类似Maven结构），除了手工建立文件结构，还可以采用sbt eclipse的配置方法。

2.1、添加sbt eclipse插件

有2种配置方式：

一种是在 ~/.sbt/0.13/plugins//build.sbt 里配置addPlugin,这种做法是全局的插件，即对本机所有sbt项目均使用。

另一种是每个项目不一样的plugins，则是在每个项目跟目录下project/plugins.sbt里进行插件配置。

victor@victor-ubuntu:~/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里面内容配置，添加插件：

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

2.2、生成eclipse项目文件

然后进入到根目录sbt,成功进入sbt，运行eclipse命令生成eclipse的.classpath等eclipse相关文件：

victor@victor-ubuntu:~/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的目录结构是相似的：

victor@victor-ubuntu:~/workspace/test_sbt$ tree src
src
├── main
│   ├── java
│   └── scala
└── test
    ├── java
    └── scala

发现没有resouces目录：

在跟目录的build.sbt里添加：

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

   再执行sbt eclipse 

victor@victor-ubuntu:~/workspace/test_sbt$ tree src/
src/
├── main
│   ├── java
│   ├── resources
│   └── scala
└── test
    ├── java
    ├── resources
    └── scala

2.3、导入Eclipse中

我们进入Eclipse，利用导入向导的import existing project into workspace这一项进行导入。

至此，我们的项目结构搭建完成，可以像开发java maven项目一样的开发scala sbt项目了。

三、开发与部署

下面准备用一个实际例子演示在Scala里开发的一般步骤，最近用到scala里的json，就用json4s这个json lib来开发一个解析json的例子，json4s地址：https://github.com/json4s/json4s

3.1、添加依赖

我们如果想使用第三方的类，就需要添加依赖关系，和GAV坐标，这个再熟悉不过，我们需要编辑根目录下的build.sbt文件，添加依赖：

这里name,version,scalaVersion要注意每个间隔一行，其它的也是，不然会出错。

libraryDependencies是添加依赖的地方：我们添加2个。

resolvers是仓库地址，这里配置了多个。

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
)

    再次运行sbt eclipse，则依赖的jar包会自动加载到classpath：

3.2、测试程序

一个简单的解析Json的程序，程序很简单，这里就不解释了。

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)))
}

    至此我们在eclipse能运行Run as Scala Application，但是如何加依赖打包发布呢？

3.3、Assembly

还记得Spark里面的assembly吗？那个就是发布用的，sbt本身支持的clean compile package之类的命令，但是带依赖的one jar打包方式还是assembly比较成熟。

Sbt本身的命令：参考 http://www.scala-sbt.org/0.13/tutorial/Running.html 和http://www.scala-sbt.org/0.13/docs/Command-Line-Reference.html

clean	Deletes all generated files (in the target directory).
compile	Compiles the main sources (in src/main/scala andsrc/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 from src/main/scala and src/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是作为一种插件的，所以要在project下面的plugins.sbt里面配置，至此plugins.sbt文件里内容如下：

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")

    除了插件的配置之外，还需要配置跟目录下build.sbt，支持assembly，在文件头部加入：

import AssemblyKeys._
assemblySettings

   至此build.sbt文件内容如下：

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
)

   运行sbt assembly命令进行发布：

> 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

  我们发现文件发布到了/home/victor/workspace/test_sbt/target/scala-2.10/shengli_test_sbt-assembly-1.0.jar

那我们来执行一下，看是否成功：

执行：

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

victor@victor-ubuntu:~/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 ]
    } ]
  }
}

   证实发布的结果是成功的。

四、总结

本文介绍了在Eclipse里利用Sbt构建开发Scala程序的一般步骤，并用实例讲解了整个流程。

用sbt eclipse插件生成sbt文件目录结构，sbt eclipse命令来生成更新jar包依赖。

用assebly插件对scala应用进行打包发布。

http://www.tuicool.com/articles/f26Bjq

 

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