Project Structure

Feature packages and thin layers

Organise packages by feature (products, orders, payments), each containing its controller, service, repository and DTOs, rather than global controllers and services packages. Keep controllers thin (HTTP concerns only), put business rules in services, and keep the @SpringBootApplication class at the root and minimal. Spring Modulith can verify module boundaries and document dependencies as the code grows.

Build services that last

Organise code by feature, keep up with Spring Boot releases, and review with a checklist.

A feature-oriented layout

Names are examples.

com.example.shop/
  ShopApplication.java          minimal main class
  products/
    ProductController.java      HTTP + DTOs
    ProductService.java         business rules, transactions
    ProductRepository.java      data access
    Product.java                entity
  orders/ ...
  config/                       security, properties, infrastructure beans

Keep the main class minimal

As the testing pitfall showed, beans on the main class leak into every test slice.

Quick check: What does package-by-feature mean?

• Grouping each feature's controller, service and repository together
• One package per annotation type
• Putting all code in the main class
• A package per developer