Code Monkeyism

Programming is hard by Stephan Schmidt

September 15, 2008

Scala, Maven and Jersey

As a small side note, I’ve got

import javax.ws.rs.{Path, GET, ProduceMime}

@Path("/hello")
class HelloResource {
  @GET
  @ProduceMime(Array("text/html"))
  def hello() =  "Hello World"
}

working with Maven2, Jetty and Jersey. Took some time but was interesting. Any ideas for Array("text/html") (Scala does’t support varags the same as Java does) Perhaps a clever implicit? Need to think more.

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Filed under: Jersey, Maven, Scala

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About the author: Stephan has been working as a head of development and CTO. He has experiences in different technologies since 20 years including Java, Rails and Python. Stephans main field of interest is maintainablity and productivity in software development. Want to know more? All views are only his own.

Comments

Daniel Spiewak

It should work as expected under 2.7.2, but until then you’re unfortunately stuck with Array(…).

September 16th, 2008
stephan

Ah, very nice, thanks.

September 16th, 2008
K

Array(”text/html”) === Array.apply(”text/html”) which is defined object Array (see http://www.scala-lang.org/docu/files/api/scala/Arrayobject.html#apply(A*)).

Although Scala does not support varargs, but it has a similar concept called “repeated parameters”

September 17th, 2008
stephan

@K: Perhaps you can help me with converting A* to Array[A]?

(which I need for a test project, not the case of the post)

September 17th, 2008
K

By default if you specified a function

def a(b:A*)

You will get b as an instance of type Array[A]

For testing purpose, you can check this in scala console.

September 18th, 2008
stephan

@K: Sure? Because I though I’ve got a Seq and people on the net suggest

def g(x: Any*) =
x.asInstanceOf[scala.runtime.BoxedObjectArray].unbox(x.getClass).asInstanceOf[Array[Object]]

(which by the way works)

September 18th, 2008
K

Sorry, my mistake.

Actually you get an instance of Seq (BoxedArray) of that repeated parameter but you can operate it (in Scala) like operating an Array.

If you want to operate it within the function as an Array (or pass it to Java), you must unboxed it using that suggestion.

If you want to pass it as an Array[Any] to another scala function what you only need to do is call x.toArray[Any]. Although you get another BoxedAnyArray, but when passing the parameter to a scala function, compiler will auto-unboxed it. Check following two function:

def a(is:Any*){
println(is.getClass)
println(is.toArray[Any].getClass)
b(is.toArray[Any])
}

def b(is:Array[Any]){
println(is.getClass)
println(is)
}

a(1, “String”)

you will get following output: (I tested this using Scala 2.7.1)
class scala.runtime.BoxedObjectArray
class scala.runtime.BoxedAnyArray
class [Ljava.lang.Object;
[Ljava.lang.Object;@1710808

Implementation of array in Scala is quite interesting, for detail see http://www.drmaciver.com/2008/06/scala-arrays/

September 19th, 2008

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