🚀 A Clean & Scalable Spring Boot Project Structure (Shared-Domain Architecture)

Organizing a Spring Boot project isn’t just about style — it directly affects how maintainable, scalable, and team-friendly your application becomes.

The classic approach:

controller/
service/
repo/
model/

…works for tiny projects, but quickly becomes messy when the app grows.

A better way for real-world full-stack apps is a Shared-Domain + Feature Modules architecture.

Here’s the structure:

src/
├── config/
├── shared/
│   ├── util/
│   ├── exception/
│   ├── model/
│   └── repo/
├── modules/
│   ├── auth/
│   │   ├── controller/
│   │   ├── service/
│   │   ├── dto/
│   │   ├── mapper/
│   │   └── projection/
│   │
│   └── dashboard/
│       ├── controller/
│       ├── service/
│       ├── dto/
│       ├── mapper/
│       └── projection/

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🧱 Folder Breakdown (Short & Useful)

config/

App-wide configurations (Security, Swagger, CORS, caching, bean configs).

shared/

Common domain layer — reusable across all features.

• model/ → JPA entities
• repo/ → shared repositories
• exception/ → global exception handlers + custom exceptions
• util/ → utilities used by multiple modules

modules/

Each feature has its own mini-architecture:

auth/
  controller/
  service/
  dto/
  mapper/
  projection/

This keeps features independent and clean.

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🎯 Why Use This Architecture?

✔ Feature-based organization → easy to navigate

✔ Shared domain avoids duplication

✔ Scales cleanly as features grow

✔ Ideal for teams working on multiple modules

✔ Easy to convert modules into microservices later

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📌 When This Works Best

Use this structure if:

• You're building a medium or large Spring Boot app
• Multiple devs will work on different features
• You want a clean way to separate features
• Some entities (User, Role, Company) need to be shared

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🏁 Final Thoughts

This Shared-Domain Architecture strikes the perfect balance:

• Not too complex
• Not too basic
• Perfect for modern full-stack development
• Easy to extend, test, and migrate

If you’re starting a new Spring Boot project or refactoring an existing one, this structure will save you time and headaches as your application grows.