Writing DAO : how to override or implements the interface methods in abstract class?

Question

I am working with Spring 3.2 and Hibernate 4. I am writing the persistence layer access with dao. Here is the dao interface code :

public interface AbstractDao<E, I extends Serializable> {

    public E findById(I id);
    public void saveOrUpdate(E e);
    public void delete(E e);
    public List<E> findByCriteria(Criterion criterion);
}

Just after I have written following the abstract class which implements the interface :

public abstract class AbstractDaoImpl<E, I extends Serializable> implements AbstractDao<E,I> {

        private Class<E> entityClass;

        protected AbstractDaoImpl(Class<E> entityClass) {
            this.entityClass = entityClass;
        }

        @Autowired
        private SessionFactory sessionFactory;

        public Session getCurrentSession() {
            return sessionFactory.getCurrentSession();
        }

        @Override
        public E findById(I id) {
            return (E) getCurrentSession().get(entityClass, id);
        }

        @Override
        public void saveOrUpdate(E e) {
            getCurrentSession().saveOrUpdate(e);
        }

        @Override
        public void delete(E e) {
            getCurrentSession().delete(e);
        }

        @Override
        public List<E> findByCriteria(Criterion criterion) {
            Criteria criteria = getCurrentSession().createCriteria(entityClass);
            criteria.add(criterion);
            return criteria.list();
        }
}

I am getting some compilation errors on all methods that i have implemented in the abstract class : findById(I id) , saveOrUpdate(E e) , delete(E e) , findByCriteria(Criterion criterion) .

The error message is :

Multiple markers at this line
- implements com.startup.app.models.hibernate.dao.AbstractDao.findById
- The method findById(I) of type AbstractDaoImpl must override a superclass method

What wrong, I don't understand. thanks.

Answer 1

Make sure that you are using atleast Java 1.6 inorder to use @Override in this case.

In Java 1.5, @Override could only be applied to methods overriding a superclass method.