I ran into a similar situation but ran into a Call Stack Overflow exception when the built-in anorm function to convert to Streams attempted to parse the result set.
In order to get around this I elected to abandon the anorm ResultSetParser paradigm, and fall back to the java.sql.ResultSet object.
I wanted to use anorm's internal classes for the parsing result set rows, but, ever since version 2.4, they have made all of the pertinent classes and methods private to their package, and have deprecated several other methods that would have been more straight-forward to use.
I used a combination of Promises and Futures to work around the ManagedResource that anorm now returns. I avoided all deprecated functions.
import anorm._
import java.sql.ResultSet
import scala.concurrent._
def SqlStream[T](sql:SqlQuery)(parse:ResultSet => T)(implicit ec:ExecutionContext):Future[Stream[T]] = {
val conn = db.getConnection()
val mr = sql.preparedStatement(conn, false)
val p = Promise[Unit]()
val p2 = Promise[ResultSet]()
Future {
mr.map({ stmt =>
p2.success(stmt.executeQuery)
Await.ready(p.future, duration.Duration.Inf)
}).acquireAndGet(identity).andThen { case _ => conn.close() }
}
def _stream(rs:ResultSet):Stream[T] = {
if (rs.next()) parse(rs) #:: _stream(rs)
else {
p.success(())
Stream.empty
}
}
p2.future.map { rs =>
rs.beforeFirst()
_stream(rs)
}
}
A rather trivial usage of this function would be something like this:
def getText(implicit ec:ExecutionContext):Future[Stream[String]] = {
SqlStream(SQL("select FIELD from TABLE")) { rs => rs.getString("FIELD") }
}
There are, of course, drawbacks to this approach, however, this got around my problem and did not require inclusion of any other libraries.