Split Active Record into Aggregate and Repository

Motivation

An Active Record (described in Patterns of Enterprise Application Architecture) is a part of the domain logic that does two things: (a) it represents a concept from the domain and (b) it manages the storage of that concept. This refactoring separates these two responsibilities from each other.

Mechanics

• Identify methods in active records as either domain logic or data access logic. If they are mixed use Extract Method first.
• Create repository class and copy all data access logic into it.
• Mark all data access methods in active record as @Deprecated or [Obsolete]or the like.
• Replace every call to a data access method of the active record with a a call to the corresponding method in the repository.
• Remove data access methods from active record thus turning it into an aggregate/entity.

Often, a follow-up step to this refactoring is to split the repository into interface and implementation.

Example(s)