JAXB解组期间，ObjectFactory的作用是什么？

JAXBContext jc = JAXBContext.newInstance( \"com.example.entities\" );
Unmarshaller u = jc.createUnmarshaller();
r = (Response )u.unmarshal( inputStream );

@XmlRegistry
public class ObjectFactory {

    public Response createRsp() {
        return new Response();
    }
}

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name=\"rsp\")
@XmlType
public class Response { ... }

@XmlType(factoryClass=ObjectFactory.class, factoryMethod=\"createRsp\")
public class Response {
}