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class-designpocomodelingpojo

What constitutes a rich domain model in a POJO/POCO?

What is the difference between

  • A simple fields-accesors-mutators class
  • A rich-modeled class

What constitutes rich modeling in business-domain classes?

Solution

  • "Rich" as used here implies "rich behavior" (as opposed to state).

    There is technical behavior and domain behavior. Accessors and mutators are technical; they lack the "why" which defines business interest.

    Domain objects represent the "why" and encapsulate the "how". Actually, all objects do that; domain objects do it specifically for business value.

    Let's say you, as an employee domain object, have to request a day off of work. You have 2 options:

    1. Tell your manager and he marks the schedule.
    2. Ask your manager for the schedule and mark it.

    Model 1 is rich. The "why" (vacation time) encapsulates the "how" (marking the schedule).

    Model 2 relegates the manager to a simple property bag and leaks the scheduling abstraction.