JAXB-Eclipselink: Mapping abstract "getter" to XML - jaxb

Question

I am using the EclipseLink implementation (2.3) of JAXB to map POJOs to XML and encountering a problem with following usecase:
public abstract class A {
public abstract Set<X> getX();
// There is no setter
}
public class B extends A {
// Set via constructor
private Set<X> x;
#Override
public Set<X> getX();
}
I am defining the mapping itself completely in an external bindings-file, i set class A to be transient like so:
<java-type name="foo.A" xml-transient="true"/>
and for class B:
<java-type name="bar.B" xml-accessor-type="PROPERTY">
<xml-root-element name="B" />
<java-attributes>
<xml-element java-attribute="x" xml-path="..."/>
</java-attributes>
</java-type>
Now, upon marshalling i am getting the exception: "Duplicate Property named [x] found on class [bar.B]"
which in my opinion is coming from the abstract declaration in A, being inherited by B.
Setting the accessor-type for B to FIELD, gets rid of this error, unfortunately this is not an option because i do have an extra property in B to marshal which does not return a field but a calculated value, so i am stuck with PROPERTY (following works: setting accessor-type for B to FIELD and mapping the extra property with an #XmlPath annotation - but i dont want annotations in my code).
Being stuck with accessor-type PROPERTY for class B, my next attempt was:
<java-type name="foo.A" xml-accessor-type="NONE"/>
to prevent the abstract property from being inherited by B, which gets me:
Ignoring attribute [x] on class [bar.B] as no Property was generated for it.
Same is happening using this mapping:
<java-type name="foo.A" xml-accessor-type="PROPERTY">
<java-attributes>
<xml-transient java-attribute="x"/>
</java-attributes>
</java-type>
In both cases property 'x' is ignored.
I have really spent quite some time on this now - i cant imagine that its not possible to get this to work??
My workaround at the moment:
Leaving foo.A to be transient, specifying accessor-type FIELD for bar.B (which gets me property 'x' without problems) and mapping the extra property in B using an annotation in code.
But as mentioned before: I would like to solve this completely without annotations - anybody any idea? Blaise? :)
regards,
--qu

Answer 1

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB 2 (JSR-222) expert group.
You appear to have hit a bug. You can track our progress on this issue at the following link. I have provided additional details on this issue below:
https://bugs.eclipse.org/367886
Using Annotations
If you were going to map this use case with JAXB/MOXy annotations you could set #XmlAccessorType(XmlAccessType.NONE) on the A class and do something like:
A
package forum8727402;
import javax.xml.bind.annotation.*;
#XmlAccessorType(XmlAccessType.NONE)
public abstract class A {
public abstract String getX();
}
B
package forum8727402;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;
#XmlRootElement
public class B extends A {
#XmlPath("a/b/c/text()")
private String x;
public B() {
x = "Hello World";
}
#Override
public String getX() {
return x;
}
#XmlElement
public String getCalculatedValue() {
return "Calculated Value";
}
}
Demo
package forum8727402;
import javax.xml.bind.*;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(B.class);
B b = new B();
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(b, System.out);
}
}
Output
<?xml version="1.0" encoding="UTF-8"?>
<b>
<a>
<b>
<c>Hello World</c>
</b>
</a>
<calculatedValue>Calculated Value</calculatedValue>
</b>
Using MOXy's External Mapping File
oxm.xml
Below is a MOXy external mapping file that represents the equivalent of the previously shown annotations:
<?xml version="1.0" encoding="UTF-8"?>
<xml-bindings
xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
package-name="forum8727402">
<java-types>
<java-type name="A" xml-accessor-type="NONE"/>
<java-type name="B">
<xml-root-element/>
<java-attributes>
<xml-element java-attribute="x" xml-path="a/b/c/text()"/>
<xml-element java-attribute="calculatedValue"/>
</java-attributes>
</java-type>
</java-types>
</xml-bindings>
Demo
The code below demonstrates how to reference the mapping file:
package forum8727402;
import java.util.*;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.JAXBContextFactory;
public class Demo {
public static void main(String[] args) throws Exception {
Map<String, Object> properties = new HashMap<String, Object>(1);
properties.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, "forum8727402/oxm.xml");
JAXBContext jc = JAXBContext.newInstance(new Class[] {A.class, B.class}, properties);
B b = new B();
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(b, System.out);
}
}
Output
[EL Warning]: 2012-01-04 14:45:46.366--Ignoring attribute [x] on class [forum8727402.xml.B] as no Property was generated for it.
<?xml version="1.0" encoding="UTF-8"?>
<b>
<calculatedValue>Calculated Value</calculatedValue>
</b>