[SOLVED] Cannot send to the browser ByteArrayOutputStream in Play for Scala

Cannot send to the browser ByteArrayOutputStream in Play for Scala

I have the following code in Play for Scala that attempts to send an Excel file to the browser:

            val out = new ByteArrayOutputStream
            val exporter = new org.pivot4j.ui.poi.ExcelExporter(out)
            val renderer = new TableRenderer
            renderer.render(model, exporter);
            out.flush
            out.close
            Ok(out).withHeaders(
                  CONTENT_TYPE -> "application/vnd.ms-excel",
                  CONTENT_DISPOSITION -> s"attachment; filename = file.xlsx")

The Ok throws a compilation error:

◾Cannot write an instance of java.io.ByteArrayOutputStream to HTTP response. Try to define a Writeable[java.io.ByteArrayOutputStream]

Even though ByteArrayOutputStream is of type output, it cannot be written. How to fix this?

Solution

Try calling toByteArray on out like so:

Ok(out.toByteArray).withHeaders(...)

DefaultWritables provides a list of Writable provided by Play out-of-the-box. In particular, there exists Writeable[Array[Byte]] which should get picked up when you call toByteArray