Helper for streaming MongoDB GridFS files in lift web applications.

GridFSHelper.scala

package code.lib

import net.liftweb._
import http._
import util._
import Helpers._
import common._
import mongodb._

import com.mongodb._
import gridfs._

import _root_.java.io.File

object GridFSHelper {    

  def get(req: Req, filename: String): Box[LiftResponse] = {    
    MongoDB.use(DefaultMongoIdentifier) ( db => {      
      val fs = new GridFS(db)
            
      fs.findOne(filename) match {
        case file:GridFSDBFile => 
          
          val lastModified = file.getUploadDate.getTime
          
          Full(req.testFor304(lastModified, "Expires" -> toInternetDate(millis + 10.days)) openOr {                              
            val headers = 
              ("Content-Type" -> contentType(filename)) ::
              ("Pragma" -> "") :: 
              ("Cache-Control" -> "") :: 
              ("Last-Modified" -> toInternetDate(lastModified)) ::
              ("Expires" -> toInternetDate(millis + 10.days)) ::
              ("Date" -> nowAsInternetDate) :: Nil
            
            val stream = file.getInputStream

            StreamingResponse(
             stream, 
             () => stream.close,
             file.getLength,
             headers, Nil, 200)
          })
        case _ => Empty
      }
    })
  }    

  private def contentType(filename:String) = 
    LiftRules.context.mimeType(filename) openOr "application/octet-stream"
}

Some description can be found here: http://mrico.eu/entry/streaming_files_from_gridfs_wit