501-frameworks-micronaut-core

Micronaut Core Guidelines

Apply Micronaut core guidelines for DI, configuration, HTTP adapters, and operations.

What is covered in this Skill?

• Thin main with Micronaut.run(Application.class, args)
• Bean scopes: @Singleton, @Prototype; request scope only when justified
• Constructor injection with jakarta.inject.Inject
• @Factory for third-party or explicit bean construction
• @ConfigurationProperties (grouped settings) vs scattered @Property
• @Requires and environments instead of env branching in domain code
• Thin @Controller types delegating to @Singleton services
• @Scheduled with explicit failure visibility
• @ExecuteOn(TaskExecutors.BLOCKING) (or virtual-thread executors) for blocking I/O off the event loop
• Netty graceful shutdown properties
• AOP interceptors for cross-cutting concerns

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

Constraints

Before applying Micronaut 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
• PREREQUISITE: Project must compile successfully before applying Micronaut core improvements
• SAFETY: If compilation fails, stop immediately — compilation failure is a blocking condition
• VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
• BEFORE APPLYING: Read the reference for detailed rules, good/bad patterns, and constraints

When to use this skill

• Review Java code for Micronaut application structure and beans
• Apply best practices for Micronaut configuration, @Requires, and factories
• Improve scheduling, shutdown, or threading in Micronaut services
• Review Micronaut dependency injection scopes and factories
• Configure Micronaut @Requires conditions for environments

Workflow

1. Read reference and assess project context

Read references/501-frameworks-micronaut-core.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/501-frameworks-micronaut-core.md.