Gzip compression of dynamic response in Play

gistfile1.scala

package plugin

import play.api._
import play.api.mvc._
import play.api.http.Writeable
import play.api.http.HeaderNames._
import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
import java.util.zip.GZIPOutputStream
import play.api.libs.concurrent.Promise

object GZip {

  def gzip(input: Array[Byte]): Array[Byte] = {
    val inputStream = new ByteArrayInputStream(input)
    val byteArrayOut = new ByteArrayOutputStream(input.length)
    val gzipper = new GZIPOutputStream(byteArrayOut)
    val buf = new Array[Byte](4096)
    var numBytesRead = inputStream read buf
    while (numBytesRead > 0) {
        gzipper.write(buf, 0, numBytesRead)
        numBytesRead = inputStream read buf
    }
    // Clean up.
    inputStream.close
    gzipper.close
    byteArrayOut.toByteArray
  }
  
  def gzipped(r: => Result)(implicit req: RequestHeader): Result = {
    req.headers.get(ACCEPT_ENCODING).map(_.split(',').exists(_ == "gzip")) match {
      case Some(true) => gzipResult(r)
      case _ => r 
    }
  }

  private def gzipResult(r: => Result)(implicit req: RequestHeader): Result =   r match {
    case s:SimpleResult[_] =>
        SimpleResult(s.header, s.body)(gzippedWritable(s.writeable)).withHeaders(CONTENT_ENCODING -> "gzip")
    case AsyncResult(p) => AsyncResult(p.map(r => gzipped(r))) 
    case _ => r
  }

  private def gzippedWritable[A](w: Writeable[A]): Writeable[A] = {
    Writeable { a =>
      gzip(w.transform(a)) 
    }
  }   
}


//And inside the controller action we could use it like following:

  def index = Action { implicit request =>
    gzipped {
      Ok(views.html.index("hey"))              
    }
  }
  
  //or
  def index = Action { implicit request =>
    gzipped {
      Async {
        Promise.pure(Ok(someJsonValue))  
      }
    }
  }