StAX XML all content between two required tags

Try

    StringWriter sw = new StringWriter();
    XMLOutputFactory of = XMLOutputFactory.newInstance(); 
    XMLEventWriter xw = null;
    XMLInputFactory f = XMLInputFactory.newInstance();
    XMLEventReader xr = f.createXMLEventReader(new FileInputStream("test.xml"));
    while (xr.hasNext()) {
        XMLEvent e = xr.nextEvent();
        if (e.isStartElement()
                && ((StartElement) e).getName().getLocalPart().equals("tagINeed")) {
            xw = of.createXMLEventWriter(sw);
        } else if (e.isEndElement()
                && ((EndElement) e).getName().getLocalPart().equals("tagINeed")) {
            break;
        } else if (xw != null) {
            xw.add(e);
        }
    }
    xw.close();
    System.out.println(sw);

prints

    <someinternalTag1>
        <someinternalTag11>
            Some text content..
        </someinternalTag11>
    </someinternalTag1>
    <someinternalTag2>
        Something here
    </someinternalTag2>

Update:

If you need XML string with too, we can write like that:

        if (e.isStartElement() &&
                ((StartElement) e).getName().getLocalPart().equals("tagINeed")){
            xw = of.createXMLEventWriter(sw);
            xw.add(e);
        } else if (e.isEndElement() &&
                ((EndElement) e).getName().getLocalPart().equals("tagINeed")){
            xw.add(e);
            break;
        } else if (xw != null) {
            xw.add(e);
        }