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

• Read reference and assess project context

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