On Sunday 24 May 2009 09:36:48 pm Andreas Joseph Krogh wrote:
> Hi all.
> Normally this kind of post would be better posted to -users, but I'm looking
> for the developers comments on this.
>
> Anyone have any experience using Scala with Struts2? I'm especially thinking
> about s:iterate and scala.List.
>
> I've managed to use s:iterate with Scala's List like this:
> <s:iterator value="%{getMyList().toArray().unbox(@java.lang.obj...@class)}"
> status="status">
> getMyList() returns a scala.List from my Scala-object, which I convert to an
> JAVA-array using toArray().unbox().
>
> This seems very hackish and it would be cool if one could make a
> "struts2-scala-plugin" which registered some kind of Iterator which the
> IteratorComponent could use, refactoring out the call to
> "MakeIterator.convert(findValue(value))" to a factory of some kind which
> checked some kind of registry for providing a proper Iterator for the
> Scala-object returned by findValue(value).
>
> Comments?
For the curious;
After some Googleing I "solved" this issue by defining a
getListAsJavaIterator() method in my Scala-object which uses "implicit
conversion" compiler-magic to define a new "iterator()" method on the
Scala-Iterable Trait:
object JavaIterableConversions {
class JavaIterator[T](itr: Iterator[T]) extends java.util.Iterator[T] {
def hasNext() = itr.hasNext
def next() = itr.next
def remove() = throw new
java.lang.UnsupportedOperationException("Remove
is not implemented in JavaIterableConversions:JavaIterator")
}
class JavaIterable[T](iterable: Iterable[T]) extends
java.lang.Iterable[T] {
def iterator() = new JavaIterator[T](iterable.elements)
}
implicit def implicitScalaIterableToJavaIterable[T](iterable :
Iterable[T]): java.lang.Iterable[T] =
new JavaIterable[T](iterable)
}
Usage:
import JavaIterableConversions._
class MyScalaClass {
@BeanProperty
var items: List[Item] = _
def getListAsJavaIterator(): java.util.Iterator[_] = {
items.iterator();
}
}
Note: the iterator() *must* be defined in the same class as the
implicit-conversion implicitScalaIterableToJavaIterable is defined/imported as
it's the scala-compiler which does it's magic here. Trying to call
items.iterator() from a JAVA-class will *not* work.
--
Andreas Joseph Krogh <[email protected]>
Senior Software Developer / CTO
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