Removing JAXBElement From Your Domain Model

JAXBElement is a JAXB (JSR-222) mechanism that stores name and namespace information in situations where this can not be determined from the value or mapping.  For example in the class below the elements billing-address and shipping-address both correspond to the Address class.  In order to be able to round trip the data we need to keep track of which element we unmarshalled.

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

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

    @XmlElementRefs({
        @XmlElementRef(name = "billing-address"),
        @XmlElementRef(name = "shipping-address")
    })
    private JAXBElement<Address> address;

}

While useful JAXBElement can get in the way if you want to use your domain model with something like JPA (which doesn't know what to do with it).  In this post I will demonstrate how you can eliminate the need for JAXBElement through the use of an XmlAdapter.

Represent String Values as Element Names with JAXB ("foo" as <foo/>)

In this example we will map a String value to an element name.  Instead of <foo>bar</foo> we want <bar/>.  We will accomplish this by using @XmlAdapter and @XmlElementRef.

JAXB and Inheritance - Using Substitution Groups

In a previous blog post I described how to leverage the xsi:type attribute to represent inheritance.  In this post I'll demonstrate how to use the element name instead by leveraging the XML Schema concept of substitution groups.