spring-boot-3

To enforce constructor injection in Spring Boot 3, declare bean dependencies as final constructor parameters, ensuring immutable wiring and mandatory dependency resolution at application startup without requiring field injection annotations.

The best way to validate typed configuration properties in Spring Boot 3 is using @ConfigurationProperties with JSR-303 validation annotations, ensuring externalized config values are type-safe and fail fast when bound.

Transactional boundaries in Spring Boot 3 should be placed at the service layer using @Transactional, ensuring database operations within service methods execute atomically while keeping controllers and repositories free from transactional logic.

Refactor Spring Boot applications by replacing field injection with final constructor parameters, migrating @Value annotations to typed @ConfigurationProperties classes with validation, and moving @Transactional annotations to service layer methods.

Spring Boot 3 does not strictly require constructor injection but strongly enforces it as a best practice pattern, ensuring dependencies are explicitly declared, immutable, and validated at startup rather than injected dynamically.

Typed @ConfigurationProperties in Spring Boot 3 provides structured, validated, and reusable configuration binding compared to @Value, ensuring properties are type-safe, validated at startup, and injected through constructor injection as grouped objects.