spring-boot-debug
Debug a Spring Boot failure
Read the stack trace from the innermost cause outward
The top exception is almost always a wrapper. Find the deepest Caused by: line first — that's the actual root cause. Diagnose from there, not from the top-level exception type.
Circular dependency (BeanCurrentlyInCreationException)
Bean A depends on Bean B, and B depends back on A. Spring Boot 2.6+ disables circular references by default, so the app fails fast at startup with the cycle printed in the log — read that printed cycle first, it names the exact beans involved.
Quick fix (use sparingly): @Lazy on one side of the injection, or spring.main.allow-circular-references=true.
Proper fix (prefer this): the cycle is a design smell — extract the shared logic both beans need into a third service, invert the dependency via an interface, or decouple with an application event. Circular dependencies signal tight coupling and an SRP violation more often than they signal a config problem.