If u want to use STAX in processing your xml file , u should know that u can only read/write from/ to xml file , but if u want to modify ur xml when exact event happen in STAX u could make processing for ur xml using DOM .
here is some example:
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLStreamReader xmlReader= factory.createXMLStreamReader(new FileReader(fileName));
int eventType;
while(xmlReader.hasNext()){
eventType= xmlReader.next();
if(eventType==XMLEvent.START_ELEMENT)
{
QName qNqme = xmlReader.getName();
if("YURTAG".equals(qNqme.toString()))
{
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
File file = new File("YOURXML.xml");
Document doc = builder.parse(file);
//make the required processing for your file.
}
}