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XmlPrettyPrinter.scala
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XmlPrettyPrinter.scala
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package org.gerweck.scala.util.stream
import scala.concurrent._
import scala.util.control.NonFatal
import java.io._
import java.util.UUID
import org.gerweck.scala.util._
import org.gerweck.scala.util.io._
import org.log4s._
import akka.NotUsed
import akka.stream.FlowShape
import akka.stream.scaladsl._
import akka.util.ByteString
/** A streaming pretty printer for XML.
*
* @author Sarah Gerweck <sarah.a180@gmail.com>
*/
object XmlPrettyPrinter {
private[this] final val defaultBufferSize = 4096
private[this] val logger = getLogger
def asFlow(spaces: Int = 2,
inputBuffer: Int = defaultBufferSize,
outputBuffer: Int = defaultBufferSize)
: Flow[ByteString, ByteString, NotUsed] = Flow fromGraph {
GraphDSL.create() { implicit b =>
val input = StreamInverter(inputBuffer)
val output = StreamInverter(outputBuffer)
val jobString = {
val jobId = if (logger.isDebugEnabled) Some(UUID.randomUUID().toString) else None
(Seq("XML formatting job") ++ jobId).mkString(" ")
}
Future {
try {
logger.debug(s"Starting $jobString")
timed(logger, jobString, Debug) {
prettyPrintXml(input.input, output.output, spaces)
}
} catch { case NonFatal(t) =>
logger.error(t)(s"Error in $jobString")
} finally {
try {
output.output.close()
} catch { case NonFatal(t) =>
logger.error(t)(s"Error when closing $jobString")
}
}
} (ioExecutorContext)
val sink = b.add(StreamConverters.fromOutputStream(() => input.output))
val src = b.add(StreamConverters.fromInputStream(() => output.input))
FlowShape(sink.in, src.out)
}
}
protected[this] def prettyPrintXml(from: InputStream, to: OutputStream, spaces: Int = 2): Unit = {
import javax.xml.transform._
import javax.xml.transform.sax._
import javax.xml.transform.stream._
try {
val transformer = TransformerFactory.newInstance().newTransformer()
transformer.setOutputProperty(OutputKeys.INDENT, "yes")
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", spaces.toString)
val result = new StreamResult(to)
val source = new SAXSource(new org.xml.sax.InputSource(from))
transformer.transform(source, result)
} catch { case NonFatal(e) =>
logger.warn(e)("Error when formatting XML")
}
}
}