I am in the process of writing a small scala wrapper around a java library.

The java library has an object QueryExecutor exposing 2 methods:

  • execute(query): Result
  • asyncExecute(query): ListenableFuture[Result]

ListenableFuture in this context is the one from the guava library.

I want my scala wrapper to return a Future[Result] instead of the java object, but I am not sure what is the best way to implement that. Here are 2 solutions I came up with:

future {
  executor.execute(query)
}

and

val p = promise[Result]
val guavaFuture = executor.asyncExecute(query)

Futures.addCallback(guavaFuture, new FutureCallback[Result] {
  def onFailure(t: Throwable) {
    p.failure(t)
  }

  def onSuccess(result: Result) {
    p.success(result)
  }
})

p.future

I am wondering which method is the best. My intuition is that the first one, while returning a Future, will still block a thread while the call to execute waits for a response, the second one looks like it should be really non blocking. Any comment on the pros/cons of each method ?

scala future
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