Changes

Summary

1. Persistence: - Added ClassFacade as constructor-argument and field to NoDatabaseObjectFacadeImplementation due to the necessity of making several consistency checks regarding the association between the instance- and the model- layer. - Extended NoDatabaseManagers getObjectfacade-Method by passing the managers class-facade as argument to the ObjectFacades-constructor call. - Also added the check if the ClassFacade is not null and has been initialized to the method extended above. - Implemented the set-methods of NoDatabaseObjectFacadeImplementation.
2. Persistence: - Replaced TODOs of several methods such as "commit" and "rollback" with appropriate comments (as we have nothing to do in these methods).
3. Persistence: - Removed unnecessary map and method dealing with transactions (which we have to ignore in this implementation) again after discussion with team partner. - Removed implementations which dealt with transactions and added appropriate in line comments. - Added comments to two fields.
4. Added "throwExceptionIfTransactionIsClosed", some methods that work with transactions and a hashmap to store all transactions to check if they are open or not
5. Persistence: - Removed unnecessary map and method dealing with transactions (which we have to ignore in this implementation).
6. Implemented the "clear"-Method, removed the LinkedList "userObjects" and added "idToUserObject"
7. Added the methods for getIntForId, getStringForId, getIdForString, getIdForInteger and created some HashMaps to store this information
8. Persistence: - Small amount of commenting - Removed single checkstyle error concerning line length
9. New comments
10. Persistence: - Added map to remember which objects for which types have been created. - Implemented findAllObjects-method. - Added mapUserTypeToEmptyListIfNotExists-method.
11. Persistence: - Added nextId-field and method which always provides the next id. - Added collection to store created UserObjects - Added Map to store UserObjects which point to the transaction they have been created within. - Implemented create()-method