Do I really need a service layer?

Question

My web application is written using Spring MVC + Hibernate.

• My model is \"Customer\" entity POJO.
• I have got a DAO object \"CustomerDAO\", its method

Answer 1

You don't need a service layer. However it helps you to

• Decouple your components
• You can enforce specific business rules in your service layer which should be agnostic to your repository
• Let a service facade one or more repositories. Let's consider the following sample

class Service {
  private DatabaseBarRepo barRepo;
  private DatabaseFooRepo fooRepo;

  @Transactional
  public void serviceRoutine() {
     barRepo.doStuff();
     fooRepo.doStuff();
  }
}

Here we let two separate repositories take part in the same transaction. This is specific for databases albeit the principles are valid for other systems as well.