How to instantiate an empty element with JAXB

Question

I use JAXB to create XML messages. The XML I need to create is (for the sake of simplicity):

Answer 1

As @Tom Hawtin - tackline said

and

is same. Parsers will give you "".

You have to to put nillable on your header annotation

@XmlElement(nillable=true, required=true)
public String getHeader() {
  return header;
}

I hope this code will generate following XML for null value.

import javax.xml.bind.*;
import javax.xml.bind.annotation.*;

@XmlRootElement
public class Request {

    public static void main(String[] args) throws JAXBException {
        final Request request = new Request();
        final JAXBContext context = JAXBContext.newInstance(Request.class);
        final Marshaller marshaller = context.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,
                               Boolean.TRUE);
        marshaller.marshal(request, System.out);
        System.out.flush();
    }

    @XmlElement(nillable=true, required=true)
    private String header;
}

prints