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

• Read reference and assess project context

Read references/303-frameworks-spring-boot-validation.md and inspect the current project setup before proposing changes.

• Gather scope and decide target improvements

Identify requested outcomes, constraints, and the minimum safe set of changes to apply.

• Apply framework-aligned changes

Implement or refactor validation-related configuration/code following the reference patterns and project conventions.

• 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.