Implement comprehensive Spring Boot application with REST API, Redis integration, and best practices

[Copilot]

Overview

This PR implements a complete Spring Boot application from scratch, demonstrating modern best practices for enterprise-grade REST API development with Redis integration, comprehensive validation, dependency injection, and extensive testing.

Features Implemented

🏗️ Project Structure & Configuration

• Maven Configuration: Spring Boot 3.x with all required dependencies (Spring Data Redis, Validation, Swagger/OpenAPI, Testcontainers)
• Application Configuration: Environment-specific YAML configurations with Redis settings, server configuration, and logging
• Package Structure: Clean separation of concerns with dedicated packages for controllers, DTOs, services, repositories, configuration, and exception handling

🌐 REST API Endpoints

Complete CRUD operations for user management:

Method	Endpoint	Description
POST	/api/v1/users	Create a new user
GET	/api/v1/users/{id}	Get user by ID
GET	/api/v1/users	Get all users (paginated)
GET	/api/v1/users/all	Get all users (no pagination)
PUT	/api/v1/users/{id}	Update user
DELETE	/api/v1/users/{id}	Delete user
GET	/api/v1/users/{id}/exists	Check if user exists
GET	/api/v1/users/stats	Get application statistics

📊 Data Transfer Objects (DTOs)

• UserCreateDTO: Input validation for user creation with comprehensive constraints
• UserUpdateDTO: Flexible partial updates with optional fields
• UserResponseDTO: Consistent API response format
• PagedResponseDTO: Generic pagination wrapper for list responses
• ErrorResponseDTO: Standardized error responses

🔧 Service Layer & Dependency Injection

• UserService Interface: Clean contract definition for business operations
• UserServiceImpl: Full implementation with proper transaction management
• Constructor-based dependency injection following Spring best practices
• Business logic separation from controller and repository layers

🗄️ Redis Integration

• Spring Data Redis: Entity mapping with @RedisHash annotations
• Custom serialization: JSON serialization with Jackson for complex objects
• Connection pooling: Lettuce connection factory with optimized pooling
• Indexed fields: Efficient querying with @Indexed on email field
• Repository pattern: Clean data access abstraction

⚙️ Custom Bean Configurations

• RedisConfig: Comprehensive Redis setup with custom serializers
• AppConfig: Demonstrates different bean scopes (singleton, prototype)
• Bean lifecycle methods: Initialization and destruction callbacks
• Custom ObjectMapper: Configured for Java 8 time types

🚨 Exception Handling

• Global Exception Handler: Centralized error handling with @RestControllerAdvice
• Custom Exceptions: Domain-specific exceptions (UserNotFoundException, UserAlreadyExistsException)
• Validation Error Handling: Detailed validation error responses
• Proper HTTP Status Codes: RESTful status code usage (200, 201, 400, 404, 409, 500)

📝 Input Validation

Comprehensive validation using Jakarta Bean Validation:

@NotBlank(message = "Email is required")
@Email(message = "Email must be valid")
@Size(max = 100, message = "Email must not exceed 100 characters")
private String email;

@Min(value = 18, message = "Age must be at least 18")
@Max(value = 120, message = "Age must not exceed 120")
private Integer age;

📚 API Documentation

• Swagger/OpenAPI 3: Interactive API documentation
• Detailed annotations: Comprehensive endpoint documentation
• Schema definitions: Clear request/response examples
• Accessible at: /api/v1/swagger-ui.html

🧪 Comprehensive Testing

• Unit Tests: Service and controller layer testing with Mockito
• Integration Tests: End-to-end testing with Testcontainers for Redis
• Test Coverage: All major functionality covered
• Example Test Structure:

  @ExtendWith(MockitoExtension.class)
  class UserServiceImplTest {
      @Mock private UserRepository userRepository;
      @InjectMocks private UserServiceImpl userService;
      // Test implementations...
  }

📖 Documentation

• Comprehensive README: Setup instructions, API usage examples, architecture overview
• Code Documentation: JavaDoc comments and inline documentation
• Configuration Examples: Sample requests and responses

Technical Highlights

🏛️ Architecture Patterns

• Repository Pattern: Clean data access abstraction
• Service Layer Pattern: Business logic separation
• DTO Pattern: Data transfer between layers
• Dependency Injection: Constructor-based injection
• Global Exception Handling: Centralized error management

🔒 Data Model

{
  "id": "uuid-string",
  "email": "user@example.com (unique, validated)",
  "firstName": "string (2-50 chars)",
  "lastName": "string (2-50 chars)",
  "age": "integer (18-120)",
  "createdAt": "2024-01-15T10:30:00",
  "updatedAt": "2024-01-15T10:30:00"
}

🚀 Quick Start

# Start Redis
docker run -d --name redis -p 6379:6379 redis:7.0.12-alpine

# Build and run application
mvn clean compile
mvn spring-boot:run

# Access Swagger UI
open http://localhost:8080/api/v1/swagger-ui.html

📋 Example API Usage

# Create a user
curl -X POST http://localhost:8080/api/v1/users \
  -H "Content-Type: application/json" \
  -d '{
    "email": "john.doe@example.com",
    "firstName": "John",
    "lastName": "Doe",
    "age": 30
  }'

# Get paginated users
curl "http://localhost:8080/api/v1/users?page=0&size=10"

Quality Assurance

• ✅ All tests passing: Unit and integration tests
• ✅ Clean build: No compilation warnings or errors
• ✅ Application startup verified: Successfully starts with proper configuration
• ✅ Code quality: Follows Spring Boot best practices
• ✅ Documentation: Comprehensive setup and usage instructions

File Structure

src/main/java/com/example/springbootapp/
├── SpringBootAppApplication.java     # Main application class
├── controller/UserController.java    # REST endpoints
├── dto/                             # Data Transfer Objects
├── service/                         # Business logic layer
├── repository/UserRepository.java   # Data access layer
├── model/User.java                  # Entity model
├── config/                         # Configuration classes
└── exception/                      # Exception handling

src/test/java/                      # Comprehensive test suite
src/main/resources/                 # Configuration files

This implementation provides a solid foundation for a production-ready Spring Boot application with modern best practices, comprehensive error handling, and extensive testing coverage.

This pull request was created as a result of the following prompt from Copilot chat.

Overview

Create a comprehensive Spring Boot application demonstrating best practices with REST API endpoints, clear DTO definitions, service layer with dependency injection, custom bean configurations, and Redis integration.

Implementation Requirements

1. Project Structure

Create a complete Spring Boot application with proper package structure:

• Main application class
• Controllers package for REST endpoints
• DTOs package for data transfer objects
• Services package for business logic
• Configuration package for custom beans
• Repository package for data access

2. Maven Configuration (pom.xml)

• Spring Boot 3.x starter dependencies
• Spring Data Redis
• Spring Boot Validation
• Swagger/OpenAPI documentation
• JUnit 5 and Testcontainers for testing
• Proper Maven plugins and properties

3. Application Configuration (application.yml)

• Redis connection configuration
• Server port and context path
• Swagger documentation settings
• Logging configuration
• Profile-specific configurations

4. REST Controller Implementation

Create a UserController with the following endpoints:

• POST /api/users - Create a new user
• GET /api/users/{id} - Get user by ID
• GET /api/users - Get all users with pagination
• PUT /api/users/{id} - Update user
• DELETE /api/users/{id} - Delete user
• Proper HTTP status codes and error handling
• Request/Response validation

5. DTO Definitions

Create clear DTOs with validation:

• UserCreateDTO - for user creation requests
• UserUpdateDTO - for user update requests
• UserResponseDTO - for API responses
• PagedResponseDTO - for paginated responses
• Validation annotations (@NotNull, @notblank, @Email, etc.)

6. Service Layer with Dependency Injection

• UserService interface and implementation
• Proper business logic separation
• Constructor-based dependency injection
• Transaction management
• Error handling and custom exceptions

7. Custom Bean Configurations

Create custom configuration classes:

• RedisConfig - Redis connection and template configuration
• AppConfig - Application-specific bean definitions
• Custom beans with different scopes (singleton, prototype)
• Bean initialization and destruction methods

8. Redis Integration

• Redis repository implementation
• Caching strategy for user data
• Redis template configuration
• Serialization/deserialization setup
• Cache eviction policies

9. Exception Handling

• Global exception handler
• Custom exception classes
• Proper error response DTOs
• Validation error handling

10. Testing

• Unit tests for services and controllers
• Integration tests with Testcontainers
• Redis integration tests
• Test configuration classes

11. Documentation

• Swagger/OpenAPI integration
• API documentation annotations
• README.md with setup instructions
• Code comments and JavaDoc

Technical Requirements

• Use Spring Boot 3.x
• Java 17 or higher
• Maven build tool
• Redis for caching/storage
• Proper error handling and validation
• Follow Spring Boot best practices
• Implement proper logging
• Include comprehensive tests

File Structure Expected

src/
├── main/
│   ├── java/
│   │   └── com/example/springbootapp/
│   │       ├── SpringBootAppApplication.java
│   │       ├── controller/
│   │       │   └── UserController.java
│   │       ├── dto/
│   │       │   ├── UserCreateDTO.java
│   │       │   ├── UserUpdateDTO.java
│   │       │   ├── UserResponseDTO.java
│   │       │   └── PagedResponseDTO.java
│   │       ├── service/
│   │       │   ├── UserService.java
│   │       │   └── UserServiceImpl.java
│   │       ├── repository/
│   │       │   └── UserRepository.java
│   │       ├── config/
│   │       │   ├── RedisConfig.java
│   │       │   └── AppConfig.java
│   │       ├── model/
│   │       │   └── User.java
│   │       └── exception/
│   │           ├── GlobalExceptionHandler.java
│   │           └── UserNotFoundException.java
│   └── resources/
│       ├── application.yml
│       └── application-test.yml
├── test/
│   └── java/
│       └── com/example/springbootapp/
│           ├── controller/
│           ├── service/
│           └── integration/
├── pom.xml
└── README.md

Acceptance Criteria

• Application starts successfully on default port
• All CRUD endpoints work correctly
• DTOs validate input properly
• Services are properly injected
• Custom beans are configured correctly
• Redis integration functions properly
• Swagger documentation is accessible
• Tests pass successfully
• Code follows Spring Boot best practices

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