I'm writing a servlet, and need to get all parameters from the request. I found request.getParameterNames
returns a java.util.Enumeration
, so I have to write code as:
val names = request.getParameterNames
while(names.hasMoreElements) {
val name = names.nextElement
}
I wanna know is there any way to convert a Enumeration
to a Seq/List
, then I can use the map
method?
Use JavaConverters
See https://stackoverflow.com/a/5184386/133106
Use a wrapper Iterator
You could build up a wrapper:
val nameIterator = new Iterator[SomeType] { def hasNext = names.hasMoreElements; def next = names.nextElement }
Use JavaConversions wrapper
val nameIterator = new scala.collection.JavaConversions.JEnumerationWrapper(names)
Using JavaConversions implicits
If you import
import scala.collection.JavaConversions._
you can do it implicitly (and you’ll also get implicit conversions for other Java collecitons)
request.getParameterNames.map(println)
Use Iterator.continually
You might be tempted to build an iterator using Iterator.continually
like an earlier version of this answer proposed:
val nameIterator = Iterator.continually((names, names.nextElement)).takeWhile(_._1.hasMoreElements).map(_._2)
but it's incorrect as the last element of the enumerator will be discarded.
The reason is that the hasMoreElement
call in the takeWhile
is executed after calling nextElement
in the continually
, thus discarding the last value.