spring-boot-3_skill

Overview

This skill captures recommended Spring Boot 3 patterns for configuration, dependency injection, transaction management, and web APIs. It codifies practical conventions to make services testable, validated, and easy to maintain. Use it as a quick guide when building or refactoring Spring Boot 3.3+ applications.

How this skill works

The skill inspects common design areas and prescribes focused patterns: prefer constructor injection, centralize configuration with @ConfigurationProperties plus validation, and place transaction boundaries on service-layer methods. It also shows lightweight controller patterns using records for DTOs and recommends avoiding field injection and scattered @Value usage. Follow the patterns to improve testability, validation, and separation of concerns.

When to use it

• When creating or refactoring a Spring Boot 3.3+ service or API
• When wiring beans to ensure clear dependencies and testability
• When externalizing configuration that needs validation and type safety
• When defining transactional behavior for business operations
• When designing REST controllers and request/response DTOs

Best practices

• Always use constructor injection to make dependencies explicit and mockable
• Define configuration with @ConfigurationProperties and @Validated for typed, testable settings
• Annotate business services (not controllers) with @Transactional to bound transactions
• Represent simple DTOs with Java records for concise, immutable data carriers
• Centralize configuration scanning (e.g., @ConfigurationPropertiesScan) rather than sprinkling @Value

Example use cases

• Create a PaymentProperties record with @ConfigurationProperties(prefix="payment") and validation annotations to hold provider and apiKey
• Implement OrderService with constructor injection and @Transactional for placeOrder business logic
• Build REST endpoints where controllers delegate to services and map request records to commands
• Refactor legacy code that uses field injection and multiple @Value-annotated fields into constructor-injected services and configuration properties
• Add validation for configuration early to fail fast on bad deployments