Question

I’m creating a simple web server in Scala and I am trying to implement event logging to an XML file. The XML Structure is thus:

<log>
      <event>
             <type>Info/Warning/Error/etc</type>
             <description>File not found etc</description>
             <file>/etc/etc.etc</file>
             <ip>1.2.3.4</ip>
             <time>12:34:56 1st Jan 2012</time>
      </event>
      <event>
             etc...
      <event>
</log>

Currently im attempting to write the XML to a file like this:

var logEvent = 
    <log>
<event>
<type>ERROR</type>
<description>The Requested File was not found</description>
<file>{path}</file>
<ip>{connection.getRemoteSocketAddress}</ip>
<time>{new Date(System.currentTimeMillis)}</time>
</event>
</log>

XML.save(logFile, logEvent, "UTF-8", true, null)

However when I check the file only the most recent even is there and refreshing the file while the server is running shows each event replaces the last one in the file.

Ive also tried using a FileOutputStream with appending enabled along with XML.writebut that inserts the XML schema before each event which stops it being recognised as a proper XML file. It also adds the root <log> tags around every event.

The only way i can think of is loading the current XML in the file, adding to it and then writing it back which seems rather inefficient to me.

Is there a simple way to append XML to a file that i’m missing?
Any help appreciated 🙂

Answer 1

If you append another log in that format, your document will be no valid XML because there is a missing top level container.

If you don’t care you can simply use java.nio.channels.FileChannel.

import java.nio._
import java.io._

def appendToFile(f: File) {
  var foutstream: Option[FileOutputStream] = None
  lazy val foutchannel = foutstream.get.getChannel
  try {
    foutstream = Some(new FileOutputStream(f, true)
    val buffer = ByteBuffer.allocate(1024)
    "this text will be appended" foreach (buffer.put(_.toByte))
    buffer.flip
    foutchannel.write(buffer)
    foutchannel.close
    foutstream.get.close
  } catch {
    case e: Exception => e printStackTrace
  }
}