Business and Data Layers Separation

• In a layered architecture or use of orms, there can be objects which are used in both business and data layers.

  • This leads to coupling of both layers

  • The Business layer should know nothing about the data layer and it's implementation. But by combing both layers (ie use of annotations or shared objects) it will.

  • This can lead to business objects, which have business logic and database logic

    • Breaking SRP

• To solve this is to use a mapping object, ie DAO.

  • So when business logic is finished with it's behaviour, it passes the object to the data layer by using another object

• Sharing Business and Data layers can be seen as a shortcut, and removal of duplication.

  • This is useful, for simple apps ie crud

  • but when the shared objects are used all over the place this can cause problems