Question

I have an application with 3 layers: GWT-RPC, Business and DAO
In every layer I have different beans. For example for a User I’d have UserRPC (for the UI), User (business) and UserDTO (to persist). At every layer change I reconvert the objects.

The main problem are the enumerations. The enumerations are exactly the same across the layers but I need to replicate them in order to keep the layer independence.

Any suggestion?

Answer 1

(Short answer)

If they are truly the same you want to create a commons project / jar . Inside here are all the things that are common to the entire application, such as utility classes, enumerations, etc.

(Long answer)

Consider the overall architecture of your system, there should not be any need to have duplicated data in any tier. If this is occurring it means there is a flaw in the design of the system and a scenario of tight coupling may be on the horizon. This is part of the reason why when developing software engineers often (should) document the interfaces (contracts / api) before doing any implementation. Once these interfaces are approved and there is limited to no chance of duplication the actual implementation can begin. This would catch the scenario of X number of enumerations, which are constants, being created at each individual tier of the application. Also, keep in mind that with enumerations that if something in your business tier changes that would impact an enumeration you must recompile the code and redeploy. You must take care to not have an enumeration being used as a catch all for all of your system constants as this is an entirely different issue you may have to deal with.