Java 8 - Split huge XML file using Stax gives unexpected results

Question

When splitting a huge XML file I saw a very nice solution using Stax and Transformer.transform(). Nice BUT I see that some tags got lost. Why is that?

An XML file with Name... gives the following result. In the EVENT occasions the element tag is ommited.

 Element: <?xml version="1.0" encoding="UTF-8"?><car><name>car1</name></car> Element: <?xml version="1.0" encoding="UTF-8"?><name>car2</name> Element: <?xml version="1.0" encoding="UTF-8"?><car><name>car3</name></car> Element: <?xml version="1.0" encoding="UTF-8"?><name>car4</name> 

How can I get the right elements? Has this to do with that transform( s, r) interferes with the input stream reading?

This is my code (which I saw in many places like this one ). There is no change when using a StringReader or a FileReader.

I expected this: loop { advance to start-tag; get access to that element } What I see is: 1st: the element + 2nd: parts of the element + repeated.

String testCars = "<root><car><name>car1</name></car><car><name>car2</name></car><car><name>car3</name></car><car><name>car4</name></car></root>";
String element = "car";
try {
    XMLInputFactory factory = XMLInputFactory.newInstance();
    XMLStreamReader streamReader = factory.createXMLStreamReader(new StringReader(testCars));
    streamReader.nextTag();
    TransformerFactory tf = TransformerFactory.newInstance();
    Transformer t = tf.newTransformer();
    while(streamReader.nextTag() == XMLStreamConstants.START_ELEMENT) {
            StringWriter writer = new StringWriter();
            StreamResult result = new StreamResult(writer);
            t.transform(new StAXSource(streamReader), result);
            System.out.println("Element: " + writer.toString());
    }
} catch (Exception e) { ... }

Answer 1

Thanks to Andreas, this is the solution:

String testCars = "<root><car><name>car1</name></car><other><something>Unknown</something></other><car><name>car2</name></car></root>";
XMLInputFactory factory = XMLInputFactory.newInstance();
try {
    XMLStreamReader streamReader = factory.createXMLStreamReader(new StringReader(testCars));
    streamReader.nextTag();
    TransformerFactory tf = TransformerFactory.newInstance();
    Transformer t = tf.newTransformer();
    streamReader.nextTag();
    while ( streamReader.isStartElement() ||
          ( ! streamReader.hasNext() && streamReader.nextTag() == XMLStreamConstants.START_ELEMENT)) {
        StringWriter writer = new StringWriter();
        StreamResult result = new StreamResult(writer);
        t.transform(new StAXSource(streamReader), result);
        System.out.println( "XmlElement: " + writer.toString());
    }
} catch (Exception e) { ... }

Input is:

<root>
  <car>
    <name>car1</name>
  </car>
  <other>
    <something>Unknown</something>
  </other>
  <car>
    <name>car2</name>
  </car>
</root>

Output is:

XmlElement: <?xml version="1.0" encoding="UTF-8"?><car><name>car1</name></car>
XmlElement: <?xml version="1.0" encoding="UTF-8"?><other><something>Unknown</something></other>
XmlElement: <?xml version="1.0" encoding="UTF-8"?><car><name>car2</name></car>