XmlstreamWriter and Jaxb for subtree w/o namespace

I am using xmlstreamwriter and jaxb in conjunction to marshall a big xml file. i am creating sub-tree with jaxb but the issue is when i marshal the sub-tree it is prefixed with default namespace as below:

<?xml version="1.0" encoding="UTF-8"?>
<MessageModel xmlns="urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19">
   <MessageHeader xmlns="" xmlns:ns2="urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19">
      <ns2:ProviderID>5922</ns2:ProviderID>
      <ns2:EffectiveDT>2016-08-08-04:00</ns2:EffectiveDT>
      <ns2:PartyCount>0</ns2:PartyCount>
      <ns2:ArrangementCount>1</ns2:ArrangementCount>
      <ns2:AppMetaDataString>ter</ns2:AppMetaDataString>
   </MessageHeader>
</MessageModel>

I am using below code for marshaling:

        StringWriter result = new StringWriter();
        MessageHeaderType messageHeaderType = createMessageHeader(objectFactory);
        JAXBElement<MessageHeaderType> element = new JAXBElement<MessageHeaderType>(new QName("MessageHeader"), MessageHeaderType.class, messageHeaderType);

        XMLStreamWriter  xmlOut = XMLOutputFactory.newFactory().createXMLStreamWriter(result);
        **//Setting default namespace** 
        xmlOut.setDefaultNamespace("urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19");
        xmlOut.writeStartDocument();
        xmlOut.writeStartElement("urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19", "MessageModel");
        xmlOut.writeNamespace("", "urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19");

        JAXBContext context = JAXBContext.newInstance(MessageHeaderType.class);
        Marshaller marshaller = context.createMarshaller();
        //marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        marshaller.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);
        marshaller.marshal(element, xmlOut);


        xmlOut.writeEndDocument();
        xmlOut.close();
        System.out.println(result.toString());

I am setting default namespace but it still creating sub-tree with namespace. what can i do to generate sub-tree with jaxb but without namespace?

Solution

The way you used QName is incorrect, I had a similar problem when I first used it.

When you simply give the localName (one String constructor), it assumes the namespace is empty. This is why MessageHeader has a tag xmlns="". Read more about that here.

The constructor you should use is this.

Replace your current QName with this one and it should work:

new QName("urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19", "MessageHeader");

Also, you don't need

xmlOut.writeNamespace("", "urn:schemas.mycompany.com/ENT/MessageModel/2013/09/19");

It's the same thing as the default namespace one.