Change Java's output format for nillable XML elements

Question

I'm using java's jaxb to create XML files from java objects. The problem I'm facing is the exact opposite as stated here: LinqToXml does not handle nillable elements as expected

In short: I want to properly depict members that are null in the resulting xml file.

I have following member in my class

  @XmlElement (name = "order-detail", nillable = true)
  private String orderDetail;

if I marshal an instance of this class, the resulting xml element is

<order-detail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>

Since also non-technicians are reading, maybe also manipulating, the file, I'd rather have it that way

<order-detail />

since I don't want to confuse them. So how can I achieve this?

UPDATE

Using an empty string instead of null

  @XmlElement (name = "order-detail", nillable = true)
  private String orderDetail = "";

yields

<order-detail></order-detail>

---

SSCCE

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

public class Example
{
  public static void main(String[] args) throws JAXBException
  {
    Data data = new Data();
    JAXBContext context = JAXBContext.newInstance(Data.class);
    Marshaller m = context.createMarshaller();
    m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
    m.marshal(data, System.out);
  }

  @XmlRootElement(name = "data")
  static class Data
  {
    private String orderDetail;

    @XmlElement (name = "order-detail", nillable = true)
    public String getOrderDetail()                  { return orderDetail;             }
    public void setOrderDetail(String orderDetail)  { this.orderDetail = orderDetail; }
  }
}

Output

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<data>
    <order-detail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</data>

Answer 1

JAXB will marshal an empty string ("") as an empty element. You could change your code so that when the field has a value of ("") the property reports a null value.

  @XmlRootElement(name = "data")
  static class Data
  {
    private String orderDetail = "";

    @XmlElement (name = "order-detail", nillable = true)
    public String getOrderDetail() {
        if(orderDetail.length() == 0) {
            return null;
        }
        return orderDetail;
    }
    public void setOrderDetail(String orderDetail)  { 
        if(null == orderDetail) {
            this.orderDetail = "";
        } else {
            this.orderDetail = orderDetail; 
        }
    }
  }

Normally an XmlAdapter is used to "fix up" values, but the JAXB reference implementation does not apply an XmlAdapter to null values.

---

Note

In short: I want to properly depict members that are null in the resulting xml file.

Any empty element is not a valid representation of null in XML.