Serving binary responses

[Yang Zhang]

How do I serve, say, an image/png in Scalatra? I can do:

contentType = "image/png"
response.getOutputStream.write(myByteArray)

but is that the Scalatra way? Thanks.

[Ross A. Baker]

If myByteArray is already in memory, that's a good option. If not,
these may be more efficient:

- If it's a File, return that from your action. You get zero-copy
from the default render pipeline.

- You can stream it to avoid materializing the whole PNG into memory:

org.scalatra.util.io.copy(pngStream,response.getOutputStream)

--
Ross A. Baker
ba...@alumni.indiana.edu
Indianapolis, IN, USA

[adazz]

Does this still work (2.9.1)? I'm trying to write to the response.getOutputStream and I'm getting, java.lang.NoSuchMethodError: org.scalatra.DynamicScope.response()Lorg/scalatra/Response;

when I try,  org.scalatra.util.io.copy(file.inputStream, response.getOutputStream)

sample code;

get("/imagetest2") {

    val theFile = ms.getTest(); //gets the file (GridFSDBFile) from a my service

    theFile match {

                 case Some(file) => {

                 println("write the new file");

                 contentType = "image/jpg"

                 file.writeTo("c:\\Temp\\myfile4.jpg")        //works but bad idea

                 //org.scalatra.util.io.copy(file.inputStream, response.getOutputStream)  //doesn't work

                  new File("c:\\Temp\\myfile4.jpg")          //works, but just a bad idea

                 }

                 case None => {

                  println ("failed");

                 }

           }

    }

[Ivan Porto Carrero]

You don't need to use any of that you can do the following:

get("/imagetest") {

  ms.getTest() map { file =>

    contentType = file.mediaType // i think a gridfs file has a content type attached to it

    file.inputStream

  } getOrElse println("failed")

}

another approach to this is to teach the render pipeline about a gridfsdbfile

class MyServlet extends ScalatraServlet {

   get("imagetest") {  

     ms.getTest

   }

   override def renderPipeline = myOwnDataTypes orElse super.renderPipeline

   def myOwnDataTypes: RenderPipeline = {

      case Some(m: GridFSDBFile) => 

         contentType = m.mediaType

         m.inputStream

   }

}

In the render pipeline you only need to return the next step. 

https://github.com/scalatra/scalatra/blob/develop/core/src/main/scala/org/scalatra/ScalatraBase.scala#L275-290

Extensions like json are also implemented using the render pipeline

[Ivan Porto Carrero]

oh you are right the inputstream bit has been removed from the renderpipeline. will add it back and publish a 2.1.1

On Saturday, September 1, 2012 5:49:52 PM UTC+2, adazz wrote: