如何将apache poi xls工作簿直接流式传输到akka http响应

Question

这是一种避免将Apache POI工作簿写入字节数组或临时文件并将其流式传输到akkahttp响应中的方法吗？

val wb = new SXSSFWorkbook(new XSSFWorkbook())
...building workbook...
val os = new ByteArrayOutputStream() //or buffered file output stream
wb.write(os) // <- can I just get from akka-http some output stream to write workbook directly to response?

Answer 1

这就是如何将Source[ByteString, _]作为路线的complete进行传递

val route: Route = get {
val (out, source) = StreamConverters.asOutputStream().preMaterialize()
writeAsync(out)
complete(HttpEntity(ContentTypes.`application/octet-stream`, source))
}

writeAsync可能看起来像这样，但你需要在这里使用new SXSSFWorkbook(new XSSFWorkbook()).write(os)

def writeAsync(out: OutputStream): Unit = {
val random = new Random()
Future {
1 until 10000 foreach { _ =>
out.write(random.nextPrintableChar().toInt)
}
out.close()
}
}

方法out.write将被阻止，直到有请求发送到Source为止。阻止超时通过asOutputStream()方法配置