# spring-boot-dependency-injection

Sets up constructor-first dependency injection patterns for Spring Boot projects. It eliminates field injection and organizes bean selection via @Primary and @Qualifier.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 3800 installs · ★ 363
- Author: giuseppe-trisciuoglio
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/giuseppe-trisciuoglio/developer-kit/tree/HEAD/plugins/developer-kit-java/skills/spring-boot-dependency-injection/SKILL.md
- Updated: 2026-09-10
- HTML: https://affpapa.org/en/nevibecode/skills/spring-boot-dependency-injection

## What it does

This skill guides Spring Boot architecture toward constructor injection with `final` fields. Mandatory collaborators are injected directly without `@Autowired` when a single constructor exists. Optional integrations use `ObjectProvider` or explicit no-op fallback implementations instead of nullable fields.

Infrastructure wiring moves into dedicated `@Configuration` classes, keeping domain services clean. When multiple beans share a type, the skill uses `@Primary` for the default and `@Qualifier` for specific variants. Attempting to hide circular dependencies behind `@Lazy` is treated as an architectural defect that needs redesign, not a quick fix.

Wiring validation follows a stepped approach. First, verify the component loads with a minimal `@SpringBootTest` and `@ContextConfiguration`. Then, test service behavior with direct constructor instantiation without starting the Spring container.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/spring-boot-dependency-injection/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/spring-boot-dependency-injection/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/spring-boot-dependency-injection/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/spring-boot-dependency-injection/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install giuseppe-trisciuoglio/developer-kit spring-boot-dependency-injection
```

2. **Manually: put the files in place**
- File: `.github/skills/spring-boot-dependency-injection/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/giuseppe-trisciuoglio/developer-kit --path plugins/developer-kit-java/skills/spring-boot-dependency-injection
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/spring-boot-dependency-injection/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/giuseppe-trisciuoglio/developer-kit/tree/HEAD/plugins/developer-kit-java/skills/spring-boot-dependency-injection/SKILL.md

## When to use it
- replace legacy field injection with clean constructor injection
- handle optional collaborators using ObjectProvider or no-op fallbacks
- disambiguate multiple bean implementations using @Primary and @Qualifier
- enable fast unit testing without spinning up the Spring container

## Example prompts
- Refactor UserService to use constructor injection with final fields instead of @Autowired on fields.
- Wire an optional NotificationGateway into ReportService using ObjectProvider and a no-op fallback.
- Create a minimal context test for UserService to verify bean wiring before adding business logic.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: abfa99f26af5dc65.

BEGIN THIRD-PARTY FILE abfa99f26af5dc65
```text
---
name: spring-boot-dependency-injection
description: Provides dependency injection patterns for Spring Boot projects, including constructor-first design, optional collaborator handling, bean selection, and wiring validation. Use when creating services and configurations, replacing field injection, or troubleshooting ambiguous or fragile Spring wiring.
allowed-tools: Read, Write, Edit, Bash, Glob, Grep
---

# Spring Boot Dependency Injection

## Overview

Provides constructor-first dependency injection patterns for Spring Boot:
- mandatory collaborators via constructor injection
- optional collaborators via `ObjectProvider` or no-op fallbacks
- bean selection via `@Primary` and `@Qualifier`
- validation via minimal context tests before full integration

## When to Use

Use this skill when:
- creating a new `@Service`, `@Component`, `@Repository`, or `@Configuration` class
- replacing field injection in legacy Spring code
- resolving multiple beans of the same type with qualifiers or primary beans
- handling optional features, adapters, or integrations without null-driven wiring
- reviewing circular dependencies or brittle context startup failures
- preparing code for direct constructor-based unit testing


## Instructions

### 1. Separate mandatory and optional collaborators

For each class, identify:
- mandatory collaborators required for correct behavior
- optional collaborators that enable integrations, caching, notifications, or feature-flagged behavior

Mandatory collaborators belong in the constructor. Optional ones need an explicit strategy such as `ObjectProvider`, conditional beans, or a no-op implementation.

### 2. Default to constructor injection

For application services and adapters:
- inject mandatory dependencies through the constructor
- keep injected fields `final`
- instantiate the class directly in unit tests without starting Spring

A single constructor is usually enough; `@Autowired` is unnecessary in that case.

### 3. Resolve optional behavior intentionally

Good options include:
- `ObjectProvider<T>` when lazy access is useful
- `@ConditionalOnProperty` or `@ConditionalOnMissingBean` when wiring should change by configuration
```
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