Clean & Layered Architecture with Spring Boot

Clean and Layered Architecture are two popular architectural patterns in software development. They provide a structured way to design applications, making them easier to understand, maintain, and test. Let's explore how these architectural patterns can be implemented in a Spring Boot application.

1. API Layer

Also known as the Presentation Layer, this layer handles incoming HTTP requests and outgoing HTTP responses. Here, we define our controllers and RESTful endpoints.

2. Application Layer

Also known as the Service Layer or Business Logic Layer, this layer contains the application's business logic. It orchestrates the application's use cases and coordinates the interaction between the API and Domain layers.

3. Domain Layer

This layer includes the core business concepts and entities. It represents the domain model and contains the business rules, independent of any specific application logic or framework. We define our domain entities, value objects, and aggregates here.

4. Infrastructure Layer

This layer deals with the technical details and provides the necessary infrastructure for the application. It includes data persistence, external services, and other technical concerns.

Visualization of Layers

Here's a simple visualization of how these layers interact:

+---------------------+
|       API Layer     |  <- Controllers
+---------------------+
           |
           v
+---------------------+
|   Application Layer |  <- Services
+---------------------+
           |
           v
+---------------------+
|     Domain Layer    |  <- Entities, Business Rules
+---------------------+
           |
           v
+---------------------+
| Infrastructure Layer|  <- Repositories, External Services
+---------------------+