Pre-Iterate Rule for the DelimitedFileConnector to merge two files and append extra column

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE Rule PUBLIC "netiq.dtd" "netiq.dtd">
<Rule name="preIterate-AspenCedar">
  <Description>
    An example Preiterate rule for the DelimitedFileConnector that
    can check stats of the file being processed against stats
    collected and persisted during the last aggregation
    in the PostIterate rule.
  </Description>
  <Signature>
    <Inputs>
      <Argument name='application'>
        <Description>
          Application being iterated.
        </Description>
      </Argument>
      <Argument name='schema'>
        <Description>
          Schema representing the data being iterated
        </Description>
      </Argument>
      <Argument name='stats'>
        <Description>
          A map passed by the connector of the stats for the file about to be
          iterated.
          Contains keys:
          fileName : (String) filename of the file about to be processed
          absolutePath : (String) absolute filename
          length : (Long) length in bytes
          lastModified : (Long) last time the file was updated Java GMT
        </Description>
      </Argument>
      <Argument name='log'>
        <Description>
          log for debugging
        </Description>
      </Argument>
    </Inputs>
  </Signature>
  <Source>
<![CDATA[
import sailpoint.api.SailPointFactory;
import sailpoint.api.SailPointContext;
import sailpoint.tools.GeneralException;
import sailpoint.tools.xml.XMLObjectFactory;
import sailpoint.object.Configuration;

import sailpoint.connector.Connector;
import sailpoint.connector.DelimitedFileConnector;
import sailpoint.object.Schema;
import sailpoint.object.Permission;
import sailpoint.tools.xml.XMLObjectFactory;
import sailpoint.tools.RFC4180LineIterator;
import sailpoint.tools.RFC4180LineParser;

SailPointContext ctx = SailPointFactory.getCurrentContext();
if ( ctx == null ) {
throw new GeneralException("Unable to get sailpoint context.");
}

HashMap appConfig = application.getAttributes();
String DEVFile = (String)appConfig.get("DEVFile");
String PRODFile = (String)appConfig.get("PRODFile");
String outputfile = (String)appConfig.get("outputfile");


//Construct the BufferedInputStream object
DataInputStream DEVbis = new DataInputStream(new FileInputStream(new File(DEVFile)));
DataInputStream PRODbis = new DataInputStream(new FileInputStream(new File(PRODFile)));
// Constructing stream to return to the connector
// Deleting old File so we can get the latest and greatest
java.io.File mergedFile = new File(outputfile);
mergedFile.delete();

// Now its time to write to the merge file
BufferedWriter outputFile = new BufferedWriter(new FileWriter(mergedFile,true));

String record;
//Keep reading from the file while there is any content
while ( ( record = PRODbis.readLine() ) != null) {
outputFile.append(record + ",Prod");
outputFile.newLine();
}
record = null;
while ( ( record = DEVbis.readLine() ) != null) {
outputFile.append(record + ",Dev/Test");
outputFile.newLine();
}
record = null;
outputFile.flush();
outputFile.close();

BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File(outputfile)));
return bis;
]]>
  </Source>
</Rule>