Apache CXF with Parameterized types

Question

I have a bunch of classes that all look the same and consist merely of an Id and a few String attributes. So I tried to generalize the creation of WebServices using Generics:

@WebService
public interface IBasicCRUDService<E extends AbstractEntity, D extends AbstractEntityDTO, ID, DAO extends IGenericDAO<E, ID>>{

    public List<D> findAll(BasicFilters filters);
    public D findById(ID id);

    @WebMethod(exclude = true)
    public void setBaseDao(DAO dao);
}

Implementation:

public abstract class BasicCRUDService<E extends AbstractEntity, D extends AbstractEntityDTO, ID, DAO extends IGenericDAO<E, ID>> extends AbstractService implements IBasicCRUDService<E, D, ID, DAO> {

    private IGenericDAO<E, ID> dao;
    private Class<E> persistentClass;
    private Class<D> dataTransferClass;


    public final DAO getDao() {
        return (DAO) dao;
    }


    public void setDao(DAO dao) {
        this.dao = (IGenericDAO<E, ID>) dao;
    }


    @SuppressWarnings("unchecked")
    public Class<E> getPersistentClass() {
        if (persistentClass == null) {
            this.persistentClass = (Class<E>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
        }
        return persistentClass;
    }

    @SuppressWarnings("unchecked")
    public Class<D> getDataTransferClass() {
        if(dataTransferClass == null) {
            this.dataTransferClass = (Class<D>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[1];
        }
        return dataTransferClass;
    }


    @Override
    @Transactional(readOnly=true)
    @WebMethod(operationName="findAll")
    public List<D> findAll(BasicFilters filters) {
        List<E> pList = dao.findAll(filters);
        List<D> dList = new ArrayList<D>();
        for(E e:pList) {
            dList.add(this.map(e, getDataTransferClass()));
        }
        return dList;
    }

    @Override
    @Transactional(readOnly=true)
    @WebMethod(operationName="findAll")
    public D findById(ID id) {
        return this.map(dao.findById(id), getDataTransferClass());
    }

}

And this would be a concrete implementation: @Service("metodologiaService") public class MetodologiaService extends BasicCRUDService implements IMetodologiaService {

    @Override
    @Autowired
    @Qualifier("metodologiaDAO")
    public void setBaseDao(IMetodologiaDAO dao) {
        super.setDao(dao);
    }

}

@WebService
public interface IMetodologiaService extends IBasicCRUDService<Metodologia, MetodologiaDTO, Integer, IMetodologiaDAO>{
    public List<MetodologiaDTO> findAll(BasicFilters filters);
    public MetodologiaDTO findById(Integer id);
}

The problem is when doing it like this it seems CXF is unable to properly map the attributes of the WebServices. For instance, when calling the findById method, I get this:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
   <soap:Body>
      <soap:Fault>
         <faultcode>soap:Server</faultcode>
         <faultstring>com.sun.org.apache.xerces.internal.dom.ElementNSImpl cannot be cast to java.lang.Integer</faultstring>
      </soap:Fault>
   </soap:Body>
</soap:Envelope>

However, if I declare the methods directly in my IMetodologiaService, it works:

@WebService
public interface IMetodologiaService extends IBasicCRUDService<Metodologia, MetodologiaDTO, Integer, IMetodologiaDAO>{
    public List<MetodologiaDTO> findAll(BasicFilters filters);
    public MetodologiaDTO findById(Integer id);
}

So it seems somehow extending interfaces is not working when using Parameterized types. Is there any way around this?

Answer 1

You'll probably need to use something like TypeTools to resolve the type arguments in this case:

public BasicCRUDService() {
  Class<?>[] typeArgs = TypeResolver.resolveRawArguments(IBasicCRUDService.class, getClass());
  persistentClass = typeArgs[0];
  dataTransferClass = typeArgs[1];
  dao = typeArgs[3];
}