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scalaplayframeworkenumeratorwriterplayframework-2.3

Play framework: how to enumerate java.io.Writer?

An external library uses java.io.Writer interface for some kind of output, and at the moment I use StringWriter to buffer all output and then Ok(writer.toString). But I'd want to avoid buffering and to stream data supplied by Writer.

How to craft a Play Enumerator based on java.io.Writer?

Solution

  • You can implement your own writer that uses a Concurrent.Channel to push data to an enumerator, let's talk code:

    class MyWriter extends java.io.Writer{
var channel : Concurent.Channel
def write(x:Array[Char], s:Int, e:Int) = {
  channel.push(x)
}
def close() = {
  channel.end()
}
def flush() = {

}
}
// every time writer.write is used it will push data to the enumeratr
var writer = new YourWriter();
val enumerator:Enumerator[Array[Char]]  = Concurrent.unicast[Array[Char]](channel => {writer.channel = channel})