302-frameworks-spring-boot-rest

# Java REST API Design Principles Apply REST API design principles for Spring Boot applications. **What is covered in this Skill?** - HTTP methods (GET, POST, PUT, PATCH, DELETE) — semantic consistency - Resource URI design - HTTP status codes - Request/response DTOs with lean contracts - API versioning (URI, header, or media type — applied consistently) - Bean Validation at the boundary (@Valid/@Validated on controller inputs, 400 on failure) - Pagination, sorting, and filtering (Page/Pageable with caps) - ISO-8601 instants with offset (OffsetDateTime, Instant) in JSON contracts - Content negotiation (JSON default; vendor media types when meaningful) - Idempotency-Key support for POST creates; 409 Conflict for collisions - ETag concurrency with If-Match/If-None-Match; 412 Precondition Failed / 304 Not Modified - HTTP caching discipline (Cache-Control, ETag, Last-Modified) - Deprecation and sunset headers (Deprecation, Sunset, Link rel="successor-version)" - Error handling - API security (TLS, authentication, authorization, input validation) - API contract: OpenAPI file as source of truth for API-first (OpenAPI Generator) - Controller advice and problem details (RFC 7807) **Scope:** Apply recommendations based on the reference rules and good/bad code examples. ## Constraints Before applying any REST API changes, ensure the project compiles. If compilation fails, stop immediately. After applying 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 good/bad patterns - **EDGE CASE**: If request scope is ambiguous, stop and ask a clarifying question before applying changes - **EDGE CASE**: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance ## When to use this skill - Review Java code for Spring Boot REST API - Apply best practices for Spring Boot REST API in Java code ## Workflow 1. **Read reference and assess project context** Read `references/302-frameworks-spring-boot-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/302-frameworks-spring-boot-rest.md](references/302-frameworks-spring-boot-rest.md).