gistfile1.java

//STANDARD CRUD WITH JPA : appropriate when you are dealing with objects used only as list of values
public class MyObjectDao extends JpaDao<MyObject> {}
public class MyObjectCRUDServices extends CRUDServices<MyObject> {
 public MyObjectCRUDServices(MyObjectDao dao) { super(dao); }
}

//BEGINNER JPA MADNESS
public class CustomerServices extends CRUDServices<Customer> {
  public CustomerServices(CustomerDao dao) { super(dao); }
  
  public List<Customer> listPremiumCustomers() {
    return dao.list(DetachedCriteria.forClass(Customer.class).add(Property.forName(“premium”).eq(true)));
    //either you have all eagerly fetched and the SQL query is inefficient
    //or during serialization you have n+1 select because you have lazy everywhere
  }
}

//INTERMEDIATE JPA
public class CustomerServices extends CRUDServices<Customer> {
  public CustomerServices(CustomerDao dao) { super(dao); }
  
  public List<TinyCustomerDto> listPremiumCustomers() {
    return TinyCustomerDto.transfert(dao.list(DetachedCriteria.forClass(Customer.class).add(Property.forName(“premium”).eq(true)).addProjectionList(“id, name”)));
    //SQL query is the same I'd write myself
  }
}

//QUERYDSL JPA
public class CustomerServices extends CRUDServices<Customer> {
  public CustomerServices(CustomerDao dao) { super(dao); }
  
  public List<TinyCustomerDto> listPremiumCustomers() {
    return dao.list(QCustomer.where(QCustomer.premium.isTrue()).list(TinyCustomerDto.class);
    //SQL query is the same I'd write myself and typesafe !!!
  }
}