A guide for building Micronaut applications, Java services that use compile-time dependency injection and support reactive HTTP and native-image deployment. It covers controllers, clients, configuration, and persistence choices.

Use it to create Micronaut projects, controllers, declarative HTTP clients, configuration classes, reactive endpoints, database connections, and native-image settings.

It provides consistent patterns for wiring services without relying heavily on runtime reflection. This helps prepare applications for reactive workloads and GraalVM native compilation.

micronaut — Skill for Claude Code and Codex by j4flmao

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add j4flmao/agent-skills --skill micronaut

Clone the repo

git clone --depth 1 https://github.com/j4flmao/agent-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/j4flmao/agent-skills/micronaut/github.svg)](https://agentmods.dev/skills/j4flmao/agent-skills/micronaut)

Your own site

<a href="https://agentmods.dev/skills/j4flmao/agent-skills/micronaut"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/micronaut/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/j4flmao/agent-skills/micronaut"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/micronaut.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 100 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,113 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00100	$0.04113
Opus 5	$0.00050	$0.02056
Sonnet 5	$0.00020	$0.00823
Haiku 4.5	$0.00010	$0.00411

Measured 9d ago against content hash d386e4a328b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

micronaut scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/backend/java/micronaut/SKILL.md · 540 lines

How it starts

The opening of the file, as written. The whole thing — 540 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Micronaut

Purpose

Build Micronaut applications with compile-time dependency injection, reactive HTTP servers, AOT compilation, GraalVM native image support, and declarative HTTP clients.

Agent Protocol

Trigger

User request includes: Micronaut, micronaut framework, micronaut DI, micronaut reactive, micronaut controller, micronaut client, micronaut native image, micronaut graalvm.

Input Context

JDK version (17+, 21+)
Micronaut version (4.x)
Build tool (Gradle, Maven)
Database (JDBC, R2DBC, MongoDB)
Features (Reactive, Declarative Client, AOT, Security)

Output Artifact

Project setup, controller pattern, DI configuration, client setup, native image config.

Response Format

Produce artifact directly. No preamble, no postamble, no explanations. No filler, no hedging.

Completion Criteria

Application class with @Singleton beans
Controller with @Get/@Post/@Body/@QueryValue
Declarative @Client for HTTP calls
Configuration via @ConfigurationProperties
Native image configuration for GraalVM
Reactive endpoints with Mono/Flux

Max Response Length

4096 tokens

Architecture Decision Trees

Micronaut vs Spring Boot vs Quarkus

Criterion	Micronaut	Spring Boot	Quarkus
Startup time	< 100ms (AOT)	2-5s (reflection)	< 200ms (AOT)
Memory footprint	~50MB	~200MB	~100MB
Native image	GraalVM first-class	Spring Native 3+	GraalVM first-class
DI approach	Compile-time (annotation processing)	Runtime (reflection)	Runtime + Quarkus Arc
Reactive support	Netty (built-in)	WebFlux	Vert.x
Gradle/Maven	Excellent	Excellent	Excellent

Decision: Fast startup + low memory → Micronaut. Full Spring ecosystem → Spring Boot. Fast + Funqy/extension-first → Quarkus.

Reactive vs Imperative Controllers

Aspect	Reactive (Mono/Flux)	Imperative (POJO)
Thread model	Event loop	Request-per-thread
Database	R2DBC (reactive)	JDBC (blocking)
Error handling	Operators (onErrorReturn)	try/catch
Testing	StepVerifier	JUnit assertions
Stack depth	Sometimes harder to debug	Predictable

Read the full file on GitHub · 540 lines

Files

What ships with it

6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 540 lines · 100 tokens per session scan A d386e4a328b1

Subscribe to this mod's changes

micronaut is a skill published in the GitHub repository j4flmao/agent-skills (22 stars, last pushed 3d ago), licensed MIT. It adds 100 tokens to every session and 4,113 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Backend and APIs Java Languages micronaut phase-7

micronaut