I’m currently working on code implementation that involves using JAXB for unmarshalling. Just an example of what my XML data looks like:

<services>  <service type="0">...</service>  <service type="1">...</service>  <service type="1">...</service> </services> 

I’m unmarshalling this to Object Services.java having List<Service>. Each service has common data like name, status, type (the attribute) and along with their own service specific data. To represent type I have created an enum Type.java.

public enum Type {  FILE("0","File"){     @Override      public Service createServiceInstance(ServiceAttributes attributes){       return FileService.createInstance(attributes);     }  },  NETWORK("1","Network"){     // overridden createServiceInstance method  }  // declaration of string type variables for typeCode and typeName  // constructor declaration with two arguments typeCode and typeName  public abstract Service createServiceInstance(ServiceAttribtes attributes); }  public class Service {   //declaration of variables representing common data;   private Type type;    // getters and setters } 

I have created one class for each of the service that extends the Service.java and having variables representing data specific to that service. An example is as below :

public class NetworkService extends Service {   private Link link;   // getters and setters   public static Service createInstance(ServiceAttributes attributes) {      NetworkService ns = new NetworkService();      ns.setName(attributes.getName());      ns.setType(attributes.getType())      ns.setLink(attributes.getLink())      return ns;   } } 

To aid the unmarshalling process, I have created a class that extends the XmlAdapter :

public class ServiceTypeAdapter extends XmlAdapter<ServiceTypeAdapter.ServiceAttributes, Service> {  public ServiceAttributes marshal(Service service) throws Exception {    // currently I need only the unmarshalling method    // And I know this will never be required. What should I do here?    // return null or throw new UnsupportedOperationException() ?    return null;  }  public Service unmarshal(ServiceAttributes serviceAttributes) {     Type serviceType = serviceAttributes.getType();     return serviceType.createServiceInstance(serviceAttributes);  }   public class ServiceAttributes {    private String name;    @XmlAttribute    private Type type;    // declaration of attributes that will be present in    // each of service classes     // getters and setters  } }