Using interfaces or not for in the persistence and service layer.

Option 1: Using interfaces

• + Implementation is separated from its implementation
• - duplicates number of files
• - more work
• - refactoring is more work

Option 2: Not using interfaces

• + less files
• + you ain't gonna need it

Chosen option 2. Spring wants one approach or the other (<tx:annotation-driven proxy-target-class="true" />). Therefore it is important to choose. We can start with option 2 and if we really need it we can migrate to option 1.