Is there a way to store the XMLStreamReader values temporarily within another XMLStreamReader for validations?

Question

I am not sure if this is possible so anyways thought of asking and getting clarified as I was unable to find anything similar to this here even after a lot of searches and trying out things. Really sorry if found a duplicate.

I am trying to parse the XML file using the XMLStreamReader. After reading I have to make few checks for my localpart based on which I need to assign this XMLStreamReader to different classes.

When I am making few checks I need to check the current localpart as well as next localpart. When I try to check the next localpart I am advancing to next element on XMLStreamReader. So I am trying to store the current XMLStreamReader within another temp XMLStreamReader but after the assignment when I try to navigate to next on the current XMLStreamReader then even the temp XMLStreamReader is changing I guess due to which I am unable to perform some of the action. Mainly I would like to perform JAXB Unmarshalling during which it's failing as its unable to get all the elements of the class.

I am aware the XMLEventReader has peek() but that is also failing so I am trying to store the current XMLStreamReader but its also not working and I read that its not most memory efficient. As my XML file can be very large I am trying to use the XMLStreamReader.

public class Main
{
    public static void main(String[] args) {
        final InputStream inputStream = Main.class.getClassLoader().getResourceAsStream("Customer.xml");
        final XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance();
        final XMLStreamReader xmlStreamReader = xmlInputFactory.createXMLStreamReader(xmlStream);
        //final JAXBContext jaxbContext = JAXBContext.newInstance("io.model.jaxb");
        //final Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        
        //Navigate to next and start of the XML Elements
        xmlStreamReader.next();
        
        //Read Until the end of the file
        while (xmlStreamReader.hasNext()) {
            
            //Check if the current `XML Tag` is "extension"
            if (xmlStreamReader.isStartElement() && xmlStreamReader.getLocalName().equalsIgnoreCase("extension")) {
                
                //Create a tempStream to store the current stream values
                //final XMLStreamReader streamReader = xmlInputFactory.createXMLStreamReader((InputStream) xmlStreamReader);
                final XMLStreamReader tempReader = xmlStreamReader;
                xmlStreamReader.next();
                
                //If the next element is "nextextension"
                if (xmlStreamReader.isStartElement() && xmlStreamReader.getLocalName().equalsIgnoreCase("nextextension")) {
                    System.out.println("Double Extension Assign to CLASS C with both extension tag");
                    //final C cInfo = unmarshaller.unmarshal(streamReader, C.class).getValue();
                }else{
                    System.out.println("Single Extension Assign to CLASS B with single extension tag");
                    //final B cInfo = unmarshaller.unmarshal(streamReader, B.class).getValue();
                }
                
            }
            
            //Move to the next
            xmlStreamReader.next();
        }
    }
}

I hope I was able to explain the issue. All I want to know if there is a way to achieve any of the below:

1. Temporarily store the current XMLStreamReader in another temp XMLStreamReader so that it can be used later.
2. If there is any other way to peek() into the next localpart within XMLStreamReader.

It would be really nice to get some inputs from experts here as I am stuck in this issue since yesterday.

Answer 1

Posting this answer as it can be useful to someone in the future. After trying a lot and researching I found we can store the stream in MutableXMLStreamBuffer.

//Store the XMLStreamReader values within the buffer
final MutableXMLStreamBuffer buffer = new MutableXMLStreamBuffer();
buffer.createFromXMLStreamReader(xmlStreamReader);

Then you can access the same using following:

buffer.readAsXMLStreamReader()