Java CDI Skill

Core CDI (Contexts and Dependency Injection) standards applicable to any CDI container. Covers dependency injection patterns, scopes, producer methods, events/observers, and interceptors.

Prerequisites

This skill applies to Jakarta CDI projects:

• jakarta.inject:jakarta.inject-api
• jakarta.enterprise:jakarta.enterprise.cdi-api

Required Imports

// CDI Core
import jakarta.inject.Inject;
import jakarta.inject.Named;
import jakarta.inject.Singleton;

// CDI Scopes
import jakarta.enterprise.context.ApplicationScoped;
import jakarta.enterprise.context.RequestScoped;
import jakarta.enterprise.context.SessionScoped;
import jakarta.enterprise.context.Dependent;

// CDI Producers and Optional Dependencies
import jakarta.enterprise.inject.Produces;
import jakarta.enterprise.inject.Instance;

// CDI Events
import jakarta.enterprise.event.Event;
import jakarta.enterprise.event.Observes;
import jakarta.enterprise.event.ObservesAsync;

// CDI Interceptors
import jakarta.interceptor.AroundInvoke;
import jakarta.interceptor.Interceptor;
import jakarta.interceptor.InterceptorBinding;
import jakarta.interceptor.InvocationContext;

// Quarkus Configuration
import org.eclipse.microprofile.config.inject.ConfigProperty;

References

• Jakarta CDI 4.1 Specification
• Jakarta EE CDI Tutorial
• Quarkus CDI Guide

Standards

• standards/basic.md — Injection, scopes, scope mismatch rule, optional dependencies, producers, error handling
• standards/advanced.md — Events, observers, interceptors

Templates

• templates/cdi-bean.java.tmpl — ApplicationScoped bean with constructor injection and Instance for optional dependencies
• templates/cdi-producer.java.tmpl — Producer method with Null Object pattern (never returns null)

Quality Rules

• Constructor injection used (never field/setter injection)
• Final fields for all injected dependencies
• Single constructor (no @Inject needed) or @Inject on injection constructor
• Appropriate scope selected for each bean
• Never inject shorter-lived scopes into longer-lived beans — use Instance<T>
• Instance<T> used for optional dependencies (not Provider<T>)
• Producer methods never return null
• Event payloads are immutable records
• Interceptors declare @Priority for deterministic ordering

Related Skills

• pm-dev-java:java-quarkus — Quarkus-specific CDI patterns, container/Docker config, security
• pm-dev-java:java-core — Core Java patterns
• pm-dev-java:junit-core — CDI testing patterns