Single DAO & generic CRUD methods (JPA/Hibernate + Spring)

Question

Following my previous question, DAO and Service layers (JPA/Hibernate + Spring), I decided to use just a single DAO for my data layer (at least at the beginning) in an appli

Answer 1

Here is an example interface:

public interface GenericDao {
    T create(T t);
    T read(PK id);
    T update(T t);
    void delete(T t);
}

And an implementation:

public class GenericDaoJpaImpl 
    implements GenericDao {

    protected Class entityClass;

    @PersistenceContext
    protected EntityManager entityManager;

    public GenericDaoJpaImpl() {
        ParameterizedType genericSuperclass = (ParameterizedType) getClass()
             .getGenericSuperclass();
        this.entityClass = (Class) genericSuperclass
             .getActualTypeArguments()[0];
    }

    @Override
    public T create(T t) {
        this.entityManager.persist(t);
        return t;
    }

    @Override
    public T read(PK id) {
        return this.entityManager.find(entityClass, id);
    }

    @Override
    public T update(T t) {
        return this.entityManager.merge(t);
    }

    @Override
    public void delete(T t) {
        t = this.entityManager.merge(t);
        this.entityManager.remove(t);
    }
}