Circular Dependencies in Spring — How to Detect and Fix

A circular dependency means ServiceA needs ServiceB to be created, and ServiceB needs ServiceA — a deadlock. Spring's response depends on the injection style.

Constructor injection

• Spring detects the deadlock immediately and throws BeanCurrentlyInCreationException at startup — a clear failure message naming all beans in the cycle
• Spring Boot 2.6+ extended this to field and setter injection by default — even those cycles now fail at startup unless you opt in with spring.main.allow-circular-references=true

Why it is a design problem

• Circular dependencies almost always signal that two classes share a responsibility that belongs in a third class
• Or they signal direct coupling where events should decouple the interaction

The three proper fixes

• Extract the shared concern into a class C — both A and B depend on C, not on each other
• Replace one direction with ApplicationEventPublisher — A publishes an event, B listens; one-way dependency remains, the cycle is gone
• Interface segregation — if B only needs one method from A, extract it into a narrow interface; B depends on the interface, not on all of A

@Lazy breaks the cycle by deferring one side but hides the design problem entirely. When someone removes the annotation during refactoring, the BeanCurrentlyInCreationException returns with no explanation of why it was there. Use @Lazy only as a temporary workaround.