Spring Boot Dependency Injection

Constructor injection is the right default for Spring, but a lot of legacy code still leans on field injection and nullable optionals. This skill walks you through separating mandatory from optional collaborators, using ObjectProvider for conditional features, and applying @Primary and @Qualifier only when you actually need them. The wiring validation section is solid: start with a minimal context test to catch bean problems before you write business logic. The no-op fallback pattern for optional dependencies is cleaner than sprinkling null checks everywhere. If you're refactoring services or onboarding someone who keeps reaching for @Autowired on fields, this gives you a concrete playbook.

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last updated: Aug 21, 2026

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Install

$ npx -y skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection --agent claude-code

Installs into .claude/skills of the current project.

Files

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

SKILL.md on GitHub