DTO, DAO and Entity ? Is Entity needed ? Best pratice with those 3?

I assume if you're using DTO and DAO, there is no need for entities, at least examples that i saw in this way. Or is it optional to have entities in this scenario ?

public interface CustomerResource {

    @GET
    @Path("/getCustomerListByUserID/{userID}")
    Response getCustomerListByUserID(@PathParam("userID") String userID);

    @DELETE
    @Path("/deleteCustomer/{customerID}")
    Response deleteCustomer(@PathParam("customerID") int customerID);

    @POST
    @Path("/updateCustomer")
    Response updateCustomer(CustomerDTO customer);
 }

public class CustomerResourceImpl implements CustomerResource{

 @Override
 public Response deleteCustomer(int customerID) {
     internalService.deleteCustomer(customerID);
 }

 @Override
 public Response getCustomerListByUserID(String userID) {
     internalService.getCustomerListByUserID(customerID);
 }

 @Override
 public Response updateCustomer(CustomerDTO customer) {
     internalService.updateCustomer(customer);
 }
}

public interface CustomerDAO extends BaseDAO<CustomerDTO> {
 
     List<CustomerDTO> getCustomerListByUserID(String userID);
 
     void deleteCustomer(Integer customerID);
 
     void updateCustomer(CustomerDTO customer);
 }

And internalService directly calls CustomerDAO

Are there anything wrong about this structure, how can it be better, is there any need for Customer entity?

Thank you so much ! Wish success for you all !