JAXB partial-unmarshalling Elements without @XMLRootElement

I am using the partial-unmarshalling example of JAXB, but I am unable to unmarshal XML-Elements which are not on the root-level (cause they don't have an @XmlRootElement tag). In my example I tried to read the shipTo-Element instead of the purchaseOrder-Element.

Normally I would work with JAXBElement unmarshal(Source source,Class declaredType) but since the example is using an UnmarshallerHandler and a XMLFilterImpl I don't know where to tell Jaxb which Class it should use.

My error message is: Caused by: javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"shipTo"). Expected elements are <{}comment>,<{}purchaseOrder>,<{}purchaseOrders>

I googled around a lot, but didn't find anything useful yet.

Here is the example code from the JaxB-Webpage:

Main.java

public class Main {
public static void main( String[] args ) throws Exception {

    // create JAXBContext for the primer.xsd
    JAXBContext context = JAXBContext.newInstance("primer");

    // create a new XML parser
    SAXParserFactory factory = SAXParserFactory.newInstance();
    factory.setNamespaceAware(true);
    XMLReader reader = factory.newSAXParser().getXMLReader();

    // prepare a Splitter
    Splitter splitter = new Splitter(context);

    // connect two components
    reader.setContentHandler(splitter);

    for( int i=0; i<args.length; i++ ) {
        // parse all the documents specified via the command line.
        // note that XMLReader expects an URL, not a file name.
        // so we need conversion.
        reader.parse(new File(args[i]).toURL().toExternalForm());
    }
}

}

Splitter.java

public class Splitter extends XMLFilterImpl {

public Splitter( JAXBContext context ) {
    this.context = context;
}

/**
 * We will create unmarshallers from this context.
 */
private final JAXBContext context;


public void s