Java Spring Development Best Practices

Core Principles

• Write clean, efficient, and well-documented Java code with accurate Spring Boot examples
• Use Spring Boot 3.x with Java 17+ features (records, sealed classes, pattern matching)
• Prefer constructor injection over field injection for better testability
• Follow SOLID principles and RESTful API design patterns
• Design for microservices architecture suitability

Project Structure

Organize code using the standard layered pattern:

project/
├── controllers/     # REST controllers
├── services/        # Business logic
├── repositories/    # Data access layer
├── models/          # Domain entities and DTOs
└── configurations/  # Spring configurations

Dependency Injection

• Use constructor injection for required dependencies
• Leverage @RequiredArgsConstructor with Lombok for cleaner code
• Keep constructors simple and avoid logic in them
• Use @Qualifier when multiple implementations exist

REST API Design

• Use appropriate HTTP methods (GET, POST, PUT, DELETE, PATCH)
• Return proper HTTP status codes
• Implement consistent error response format
• Use DTOs to control API contract
• Version APIs when needed

Data Access

Spring Data JPA

• Define proper entity relationships (@OneToMany, @ManyToOne, etc.)
• Use lazy loading appropriately to avoid N+1 queries
• Implement pagination for large result sets
• Use query methods and @Query for custom queries

Database Migrations

• Use Flyway or Liquibase for schema migrations
• Version migration scripts properly
• Never modify existing migrations
• Test migrations in development before production

Security

Spring Security

• Implement authentication and authorization properly
• Use BCrypt for password encoding
• Configure CORS appropriately
• Protect endpoints based on roles/permissions
• Use HTTPS in production

Secure Coding

• Validate all user inputs
• Sanitize data to prevent injection attacks
• Avoid exposing sensitive information in responses
• Use parameterized queries

Testing

Unit Testing

• Use JUnit 5 for unit tests
• Mock dependencies with Mockito
• Test business logic thoroughly
• Follow Given-When-Then pattern

Integration Testing

• Use @SpringBootTest for integration tests
• Use MockMvc for web layer testing
• Test database operations with test containers
• Test security configurations

Performance

Caching

• Use Spring Cache abstraction
• Configure appropriate cache providers (Redis, Caffeine)
• Set proper TTL for cached data
• Implement cache eviction strategies

Async Processing

• Use @Async for non-blocking operations
• Configure thread pools appropriately
• Handle exceptions in async methods
• Consider using reactive patterns for high concurrency

Logging and Monitoring

Logging

• Use SLF4J with Logback
• Log at appropriate levels
• Include correlation IDs for tracing
• Avoid logging sensitive data

Monitoring

• Use Spring Boot Actuator for health and metrics
• Export metrics to monitoring systems
• Set up proper health checks
• Monitor application performance

API Documentation

• Use Springdoc OpenAPI for API documentation
• Document all endpoints with descriptions
• Include request/response examples
• Keep documentation up to date with code