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.