Entity Manager

[tsutomi]

The Repository pattern provides several functions to access data sources, but it doesn't provide added value for the validation and management of those data.
For instance, a Repository doesn't check if an entity exists before adding it to the database, and if this happens an exception denoting conflict will be raised.

The scope of an Entity Manager is to provide a service that would operate some validations and checks before writing operations, ensuring the consistency of data, without throwing an exception, but instead returning an object describing the state of the operation (eg. Success, Failure, Unchanged, etc.).