XML Stream sample

event.txt

        XMLInputFactory xif = XMLInputFactory.newFactory();
        XMLOutputFactory xof = XMLOutputFactory.newFactory();

        try (InputStream in = new FileInputStream("/home/rafael/foo.xml")) {
            XMLEventReader xer = xif.createXMLEventReader(in);
            XMLEventWriter xew = xof.createXMLEventWriter(System.out);

            JAXBContext jc = JAXBContext.newInstance(Bar.class);

            Unmarshaller unmarshaller = jc.createUnmarshaller();
            Marshaller marshaller = jc.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, false);

            while (xer.hasNext()) {
                if (!xer.peek().isCharacters() || !xer.peek().asCharacters().isWhiteSpace()) {
                    if (xer.peek().isStartElement() && xer.peek().asStartElement().getName().getLocalPart().equals("bar")) {
                        Bar bar = (Bar) unmarshaller.unmarshal(xer);
                        bar.qux = "abc";
                        marshaller.marshal(bar, xew);
                    } else {
                        xew.add(xer.nextEvent());
                    }
                } else {
                    xer.nextEvent();
                }
            }

            xer.close();
            xew.close();
        }
        System.out.flush();

stream.txt

        XMLInputFactory xif = XMLInputFactory.newFactory();
        JAXBContext jaxbContext = JAXBContext.newInstance(Bar.class);
        String rootTag = "foo";

        try (InputStream in = Main2.class.getResourceAsStream("/foo.xml")) {
            XMLStreamReader xer = xif.createXMLStreamReader(in);

            if (xer.nextTag() != XMLStreamConstants.START_ELEMENT) {
                throw new IllegalStateException("1");
            } else if (!xer.getName().getLocalPart().equals(rootTag)) {
                throw new IllegalStateException("2");
            }

            Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
            while (xer.nextTag() == XMLStreamConstants.START_ELEMENT) {
                Bar bar = (Bar) unmarshaller.unmarshal(xer);
                System.out.println(bar.qux);
            }

            if (!xer.getName().getLocalPart().equals(rootTag)) {
                throw new IllegalStateException("3");
            }
            while (xer.hasNext()) {
                if (xer.next() == XMLStreamConstants.START_ELEMENT) {
                    throw new IllegalStateException("4");
                }
            }
        }