Question

I’m having a good time learning Scala, but I’m having the hardest time grasping how to set up a development environment.

In Ruby

• File hierarchy

  my_app/
    |
    +-- Gemfile
    +-- app.rb
  

• Gemfile

  source :rubygems
  gem "mechanize"
  

• app.rb

  require "mechanize"
  agent = Mechanize.new
  page = agent.get("http://google.com")
  

• Install dependencies and run it

  $ bundle install
  $ ruby app.rb
  

What’s the Scala equivalent with sbt?

I’m reading about sbt and how packages/imports/jar dependencies work in Java/Scala, but I can’t seem to filter out the bare bones necessities.

• What’s the minimal file hierarchy to replicate the above with Scala?
• Here’s the Java Mechanize lib available on Maven: http://search.maven.org/#search|ga|1|mechanize

• Once you run sbt and download the Mechanize dependencies, how to you discern the necessary import statements you need to get this to work?

  val agent = new MechanizeAgent
  val page: HtmlDocument = agent.get("http://www.google.com")
  

I got the above working in Eclipse by manually importing the .jars and then importing packages from the libraries until the compiler/runtime errors stopped and the agent worked. But that experience was discouraging and I’ve come here to repent.

Intent of this question: The Java ecosystem/workflow is overwhelming to me as someone that’s used to Ruby’s effortless, IDEless workflow. I think a bare bones equivalent would give me a place to start building upon.

Ideally, I’d like to get Scala development working with just Vim and the command line before becoming dependent on Eclipse.

Answer 1

I’d like to go a step farther than ffk’s answer, do much more hand-holding, and actually provide the direct translation of the Ruby example to Scala + sbt.

• File hierarchy

  Crawler/
    +- build.sbt
    +- src/
       +- main/
          +- scala/
             +- Crawler.scala
  

• build.sbt

  libraryDependencies += "com.gistlabs" % "mechanize" % "0.11.0"
  

• Crawler.scala

  import com.gistlabs.mechanize.MechanizeAgent
  import com.gistlabs.mechanize.document.Document
  
  object Crawler extends App {
    val agent = new MechanizeAgent
    val page: Document = agent.get("http://google.com")
  }
  

• Install dependencies and run it

  $ sbt run
  

To make the project importable into Eclipse or IntelliJ, you need the sbteclipse-plugin or sbt-idea plugin. But rather than having to declare these plugins in every build.sbt for every new project, you can declare them in a global build.sbt:

// in ~/.sbt/plugins/build.sbt
addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.1.0")
addSbtPlugin("com.github.mpeltonen" % "sbt-idea" % "1.2.0")

Then, back in your Scala app’s root directory:

$ sbt eclipse
or
$ gen-idea

Afterwards, you should be able to open it in the respective IDE.

Note: Whenever you add dependencies in your build.sbt, you’ll need to rerun the sbt eclipse/gen-idea command so the IDE can pick it up.