What is a Circular Dependency in Spring and how do you resolve it? स्प्रिंग में सर्कुलर डिपेंडेंसी क्या है और इसे कैसे हल करें?

A circular dependency occurs when Bean A depends on Bean B, and Bean B depends back on Bean A (directly or through a longer chain), creating a cycle the container can't resolve through straightforward constructor injection since neither bean can be fully constructed first.

With constructor injection, Spring throws a BeanCurrentlyInCreationException at startup, surfacing the design problem immediately. Common fixes include refactoring to remove the cycle (usually the correct fix — it often signals a design smell), switching one side to setter/field injection so Spring can inject after both beans partially exist, or using @Lazy on one of the dependencies so it's only resolved on first use rather than at construction time.

@Service
public class ServiceA {
    private final ServiceB serviceB;
    public ServiceA(@Lazy ServiceB serviceB) { this.serviceB = serviceB; }
}