Quarkus REST API Guidelines

Apply REST API design principles on Quarkus using Jakarta REST (JAX-RS).

What is covered in this Skill?

• Resource classes, @Path, HTTP method mapping, and resource URI design
• Status codes, Location headers, and Response building
• DTOs and Bean Validation at the boundary; ISO-8601 for date/time fields
• ExceptionMapper for consistent error JSON (RFC 7807 Problem Details)
• API versioning strategies (URI path, Accept header)
• Idempotency with Idempotency-Key header
• Optimistic concurrency: ETag, If-Match, If-None-Match
• HTTP caching with Cache-Control headers
• API deprecation: Sunset and Deprecation headers
• Pagination, sorting, and filtering query parameters
• Optional /openapi via SmallRye; API-first contract maintained in openapi.yaml (codegen)
• Reactive vs blocking considerations; @RunOnVirtualThread
• Security integration at the filter layer

Scope: Apply recommendations based on the reference rules and good/bad code examples.

Constraints

Before applying REST changes, ensure the project compiles. After applying improvements, run full verification.

• MANDATORY: Run ./mvnw compile or mvn compile before applying any change
• PREREQUISITE: Project must compile before applying REST API improvements
• SAFETY: If compilation fails, stop immediately
• BLOCKING CONDITION: Compilation errors must be resolved by the user before proceeding
• 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

• Review or improve JAX-RS resources in a Quarkus project
• Design HTTP APIs with validation and error handling on Quarkus
• Add API versioning, idempotency, ETag concurrency, or deprecation headers
• Implement pagination, sorting, or RFC 7807 Problem Details error responses

Workflow

1. Read reference and assess project context

Read references/402-frameworks-quarkus-rest.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 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/402-frameworks-quarkus-rest.md.