Kotlin Spring Boot Backend Application

A modern RESTful API built with Kotlin and Spring Boot demonstrating best practices.

Features

• RESTful API with proper response handling
• Layered architecture (Controller, Service, Repository)
• Entity relationships with JPA
• Exception handling
• CORS configuration
• Database integration (H2 in-memory)
• API documentation
• Data Transfer Objects (DTOs)
• Transactional operations
• Lombok integration for reduced boilerplate

Technologies

• Kotlin 1.9.0
• Spring Boot 3.1.0
• Spring Data JPA
• H2 Database
• Gradle with Kotlin DSL

Getting Started

Prerequisites

• JDK 17 or later
• Gradle 7.6+ (or use the included Gradle wrapper)

Running the Application

1. Clone the repository
2. Navigate to the project directory
3. Run with Gradle:

./gradlew bootRun

Or on Windows:

gradlew.bat bootRun

The application will be available at http://localhost:8080

API Endpoints

Method	URL	Description
GET	/api/v1/users	Get all users
GET	/api/v1/users/{id}	Get user by ID
POST	/api/v1/users	Create a new user
PUT	/api/v1/users/{id}	Update an existing user
DELETE	/api/v1/users/{id}	Delete a user
GET	/api/v1/users/search	Search users by name
GET	/api/v1/users/recent	Get recently added users

H2 Console

The H2 console is enabled and available at http://localhost:8080/h2-console

• JDBC URL: jdbc:h2:mem:testdb
• Username: sa | Password: blank

Project Structure

src/
├── main/
│   ├── kotlin/
│   │   └── com/
│   │       └── example/
│   │           ├── Application.kt
│   │           ├── AppConfig.kt
│   │           ├── User.kt
│   │           ├── UserController.kt
│   │           ├── UserDto.kt
│   │           ├── UserRepository.kt
│   │           ├── UserService.kt
│   │           └── GlobalExceptionHandler.kt
│   └── resources/
│       └── application.properties
└── test/
    └── kotlin/
        └── com/
            └── example/
                └── UserControllerTests.kt

Best Practices Implemented

1. Architecture

   • Separation of concerns (Controller, Service, Repository)
   • Use of interfaces for loose coupling
   • Proper exception handling

2. API Design

   • RESTful principles
   • Proper HTTP status codes
   • DTOs for request/response separation

3. Kotlin Best Practices

   • Immutable data classes
   • Extension functions
   • Null safety
   • Function expressions

4. Performance

   • JPA optimizations
   • Transaction management
   • Connection pooling

5. Security

   • CORS configuration
   • Input validation
   • Error handling without exposing sensitive information

License

This project is licensed under the MIT License