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.