Using Scala in Webwork/Struts 2, Part 1

I have been searching for a language to learn, in addition to java, for 3 years now. For various reasons I wont get into (there are enough blogs about that topic as it is), none of them totally excited me for one reason or another, until I started reading about Scala the end of 2007.

I bought the Scala book from Artima and have read a bit of it, and also read Daniel's excellent Scala intro series. I havent yet read them for comprehension..just reading to get a feel for what Scala can do. I have to admit, so far, the potential of Scala excites me like Java did when i first started playing with it 10 years ago.

So..i sat down last night and decided to see if Scala would play nice with Webwork (we havent yet migrated to Struts 2, but i imagine if this code works in WebWork 2.2, it should work in Struts 2). Amazingly enough, Scala worked just fine with WebWork. The code is dumb, as I dont know enough Scala to be clever. Besides, I wanted to try the simplest thing i could first, to see what was possible.

I was able to subclass ActionSupport, wire it up in xwork.xml, and the action was called correctly and the jsp was displayed. Next i tried setting a field in my Scala action class, to see if webwork could set params, and if i would be able to access them in the jsp using the jstl expression language. I didnt really expect it to work, but to my surprise, it did! I havent tried anything more complicated yet, but i have proven that i can write a WebWork action in Scala, and WebWork will still set the variables for me from the request, and make them available in the jsp. Pretty sweet! I hope to try some more complicated integration over the next week or two and will blog the results.

For those of you who would like to see some sample code to try yourself, here are the steps/code i used.

1) Install Scala :)
2) I modified my Ant build based on the nice tutorial here (this also takes care of copying the 2 scala lib jars to my tomcat webapp directory).
3) I had to modify my NetBeans 6 project to included my build directory, so that it could find my compiled Scala class (and yes, code completion worked).
4) Created my ugly yet simple Scala Action class (ScalaTest2.scala):

import com.opensymphony.xwork.ActionSupport

class ScalaTest2 extends ActionSupport {
 private var greeting:String = "bubba"
  override def execute():String = {
    println("hello from scala.....")
    println("Greeting" + greeting)
    "success"
  }

  def getGreeting():String = {
    greeting   
  }

  def setGreeting(greet:String):Unit = {
    greeting = greet
  }
}

Sorry about the formatting (how do you retain formatting when pasting code in a blog?). To get Webwork to set the parameter and make it available via the jsp, i had to use java style getters and setters. I bet there is a way around it doing something different in Scala, but again, my Scala knowledge is limited, and i wanted to test the simplest case i could to see if it would work at all). Notice i intialized greeting to a value, just to prove the value was getting overridden by WebWork from the request parameter. The println statements in the action was just to give me some serverside feedback.

5) Added a snipped to xwork.xml

<action name="scala" class="com.weather.vacationrentals.web.action.ScalaTest2">
<interceptor-ref name="fgBasicStack"/>
<result name="success">/pages/layouts/scalaTest.jsp</result>
</action>


Note that the interceptor is our custom stack (no relevance here yet) and this is declared in the webapp named "vacationrentals" and the webwork package "svc"

6) the jsp:

Hello from the scala action result: ${greeting}


7) Access the page via http://localhost/vacationrentals/svc/scala?greeting=steve

8) you get a page that says Hello from the scala action result: steve

Sweet! Again, this is a hello world type example, but it does show that it is possible to easily write WebWork actions in Scala with minimal work. I wont include the code here, but i wrote a utility class in Scala, and called it from a java WebWork action with no problems, too.

I cant wait to try a more complex integration when i get a bit of free time. I also need to learn enough Scala to write Scala, not Scala looking like Java.

Update: Thanks to Tom's tip in the comments, the Scala class can be rewritten (to remove the getter/setter) as:

import com.opensymphony.xwork.ActionSupport

class ScalaTest2 extends ActionSupport {
  @scala.reflect.BeanProperty
  private var greeting:String = "bubba"

  override def execute():String = {
    println("hello from scala2...")
    println("Greeting" + greeting)
    "success"
  }
}