EclipseLink MOXy: How to match XML structure variant to same bean model

Question

XML Variant 1:

<root>
  <elements>
    <element />
  </elements>
</root>

XML Variant 2:

<root>
  <element />
</root>

The bean structure is a class for each of the elements in XML Variant 1, which nest each other as shown.

The desired behavior is for the unmarshaller to create the same beans for Variant 2 as for Variant 1. That means, it should create a Elements class even though it is not existent in the structure.

Here's the bindings I use for Variant 1:

<xml-bindings
xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
package-name="demo">
<java-types>
    <java-type name="Root">
        <xml-root-element name="root"/>
        <java-attributes>
            <xml-element java-attribute="elements" xml-path="elements" type="demo.Elements"/>
        </java-attributes>
    </java-type>
    <java-type name="Elements">
        <java-attributes>
            <xml-element java-attribute="element" xml-path="element" type="demo.Element" container-type="java.util.List"/>
        </java-attributes>
    </java-type>
    <java-type name="Element" />
</java-types>

I tried adapting xml-path="elements" to xml-path="." and thought that may work for Variant 2, but without success. What's the easiest way to accomplish what I want?

Answer 1

You could use multiple mapping files for your use case.

Mapping File - Variant 1

<?xml version="1.0"?>
<xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="demo"
    xml-accessor-type="FIELD">
    <java-types>
        <java-type name="Root">
            <xml-root-element/>
        </java-type>
    </java-types>
</xml-bindings>

Mapping File - Variant 2

<?xml version="1.0"?>
<xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="demo"
    xml-accessor-type="FIELD">
    <java-types>
        <java-type name="Root">
            <xml-root-element/>
            <java-attributes>
                <xml-element java-attribute="elements" xml-path="."/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

Demo

In the demo code below we will create two different instances of JAXBContext for the same domain model with different metadata.

package demo;

import java.io.File;
import java.util.*;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.JAXBContextProperties;

public class Demo {

    public static void main(String[] args) throws Exception {
        // VARIANT #1
        Map<String, Object> properties1 = new HashMap<String, Object>(1);
        properties1.put(JAXBContextProperties.OXM_METADATA_SOURCE, "demo/oxm1.xml");
        JAXBContext jc1 = JAXBContext.newInstance(new Class[] {Root.class}, properties1);
        Unmarshaller unmarshaller1 = jc1.createUnmarshaller();
        File variant1 = new File("src/demo/variant1.xml");
        Root root = (Root) unmarshaller1.unmarshal(variant1);

        // VARIANT #2
        Map<String, Object> properties2 = new HashMap<String, Object>(1);
        properties2.put(JAXBContextProperties.OXM_METADATA_SOURCE, "demo/oxm2.xml");
        JAXBContext jc2 = JAXBContext.newInstance(new Class[] {Root.class}, properties2);
        Marshaller marshaller2 = jc2.createMarshaller();
        marshaller2.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller2.marshal(root, System.out);
     }

}