java - Jaxb: How to replace a class/binding in given object tree while unmarshalling

Question

I have a given set of classes to unmarshall a xml into an object tree. Now I get a extended xml and want to replace one class in the object tree with an extended version.

XML file

<?xml version="1.0" encoding="UTF-8"?>
<RootNode_001>
    <systemId>on the 4</systemId>
    <systemName>give me some more</systemName>
    <person>
        <firstname>James</firstname>
        <lastname>Brown</lastname>
        <address>
            <street>Funky</street>
            <city>Town</city>
            <type>HOME</type> <!-- this is the new field -->
        </address>
    </person>
</RootNode_001>

I create a new address class with the new field like this:

public class ExtAddress extends Address {
    // inherit from address and add new field
    private String type;

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }
}

Now I try to unmarshall into an object tree and I expect ExtAddress to be part of the tree like this:

public class Runner {

    public static void main ( String argv[] ) throws Exception {
        File file = new File( "basic.xml" );
        Class cls = RootNode.class;

        // create a context with the root node and the replacement class
        JAXBContext jaxbContext = JAXBContext.newInstance( ExtAddress.class, cls );
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        JAXBElement jaxbElement = unmarshaller.unmarshal( new StreamSource( file ), cls );
        RootNode rootNode = (RootNode) jaxbElement.getValue();

        System.out.println( rootNode.getClass().getName() );
        System.out.println( rootNode.getPerson().getClass().getName()  );
        // this returns Address but I want ExtAddress
        System.out.println( rootNode.getPerson().getAddress().getClass().getName()  );
    }
}

I use no annotations so far. The unmarshalled object tree return Address and not ExtAddress. If I add a XmlType annotation I get an exception:

@XmlTyp( name = "address" )
ExtAddress extends Address {
  ...
}

Exception in thread "main" com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
Two classes have the same XML type name "address". Use @XmlType.name and @XmlType.namespace to assign different names to them.
    this problem is related to the following location:
        at jaxb.standard.Address
        at jaxb.ExtAddress

I tried many things but this seems to be very near to a solution. How can I tell jaxb to use an inherited class instead of the original one.

I want to delvier a set of standard classes in a library and be able to change the object tree later as an extension when new fields in xml appear.

Answer 1

Changing the xml with extAddress instead address will do the trick.