Download Excel as xlsx instead of zip format in Scalatra

Question

I'm writing the Excel Workbook created using Apache POI to the response object directly as follows without creating a file:

val outputStream: ByteArrayOutputStream = new ByteArrayOutputStream()
workbook.write(outputStream)
ExcelOk(response.getOutputStream.write(outputStream.toByteArray))

But once the size of the response exceeds 8kB, it starts getting downloaded as zip file in Chrome and as octet-stream in FireFox.

My ExcelOk object looks like this:

object ExcelOk {
  def apply(body: Any = Unit, headers: Map[String, String] = ExcelContentType, reason: String = "") = {
    halt(ActionResult(responseStatus(200, reason), body, headers ))
  }
}

and my ExcelContentType(i.e, response headers) is as below:

val ExcelContentType = Map(
  "Access-Control-Allow-Credentials" -> "true",
  "Access-Control-Allow-Methods" -> "GET, PUT, POST, DELETE, OPTIONS",
  "Access-Control-Allow-Origin" -> "*",
  "Access-Control-Max-Age" -> "1728000",
  "Content-type" -> "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
  "Content-disposition" -> "attachment; filename=excel_report.xlsx"
)

I even tried adding "Transfer-Encoding" -> "chunked" to the header list but it doesn't work.

I added this snippet in my web.xml file as well but it didn't help either:

<mime-mapping>
  <extension>xlsx</extension>
  <mime-type>application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</mime-type>
</mime-mapping>

Any help regarding this would be useful. Note that this behavior is observed only after response size exceeds certain threshold.

Answer 1

You have to set response headers before writing content to response output stream.

response.setHeader("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
response.setHeader("Content-disposition", "attachment; filename=excel_report.xlsx")

workbook.write(response.getOutputStream)