Domain Driven Design

• An approach to software development
  • focuses on modeling complex business domains
  • aligning software design with business logic.

Core Principles

1. Focus on the Domain
   • Understand the business problem, not just the technical implementation.
   • Collaborate closely with domain experts (stakeholders, business analysts).
2. Ubiquitous Language
   • Use shared language between developers and domain experts.
   • Terms used in code should match business terminology.
3. Bounded Contexts
   • A logical boundary where a particular model applies.
   • Different parts of the system may have different models.
4. Modeling the Domain
   • Represent the real-world business rules, entities, and processes in code

Development flow:

1. Define the domain.
2. Define the Ubiquitous Language. (Dictionary)
   1. List the Nouns (Entities/Values) and Verbs (Actions) that are essential for this system
3. Pick the Aggregate Root. ("boss" object that controls consistency)
   1. When some event happen, always access this.
4. Create the Aggregate Root Model class.
   1. Not using JPA annotation. (@Table, @Column, @Id)
   2. No lombok (except for @AllArgsConstructor).
   3. No created_at, update_at.
   4. Still use UUID.
   5. One field is referencing child entity id.
   6. Set getter if needed.
   7. final for the fields.
5. Add the behaviour in Aggregate Root.
6. Create Factory method for Aggregate Root.
7. Create Repository.
   • Do NOT extend JpaRepository or CrudRepository
   • Do NOT use any Spring annotations (@Repository) here.
8. Go to infrastructure folder, create Aggregate Root entity class, ****which is entity version.
   1. Use JPA annotation. (@Table, @Column, @Id)
   2. Use lombok (except for @AllArgsConstructor).
   3. Use created_at, update_at.