303-frameworks-spring-boot-validation

# Spring Boot Validation Guidelines Apply Spring Boot validation best practices at API boundaries. **What is covered in this Skill?** - Bean Validation annotations on DTOs and command models - @Valid / @Validated on controllers and method parameters - Validation groups for create/update workflows - Custom constraint annotations and validators - Consistent 400 error responses for validation failures **Scope:** Apply recommendations based on the reference rules and good/bad examples. ## Constraints Before applying validation changes, ensure the project compiles. After improvements, run full verification. - **MANDATORY**: Run `./mvnw compile` or `mvn compile` before applying any change - **SAFETY**: If compilation fails, stop immediately - **VERIFY**: Run `./mvnw clean verify` or `mvn clean verify` after applying improvements - **BEFORE APPLYING**: Read the reference for detailed rules and examples ## When to use this skill - Add validation support in Spring Boot - Review Spring Boot validation rules - Improve request validation in Spring Boot REST APIs - Add custom Bean Validation constraints in Spring Boot - Validate configuration properties in Spring Boot - Improve nested DTO validation in Spring Boot ## Workflow 1. **Read reference and assess project context** Read `references/303-frameworks-spring-boot-validation.md` and inspect the current project setup before proposing changes. 2. **Gather scope and decide target improvements** Identify requested outcomes, constraints, and the minimum safe set of changes to apply. 3. **Apply framework-aligned changes** Implement or refactor validation-related configuration/code following the reference patterns and project conventions. 4. **Run verification and report results** Execute appropriate build/tests and summarize what changed, what was verified, and any follow-up actions. ## Reference For detailed guidance, examples, and constraints, see [references/303-frameworks-spring-boot-validation.md](references/303-frameworks-spring-boot-validation.md).