Solving Circular Dependencies: @Lazy Is Just a Workaround

Situation

While implementing the Gift API at Kakao Tech Campus, a circular dependency occurred.

MemberService → WishlistService → MemberService

Spring threw BeanCurrentlyInCreationException.

---

Quick Fix: @Lazy

First attempt was using @Lazy annotation.

@Service
public class WishlistService {
    private final MemberService memberService;

    public WishlistService(@Lazy MemberService memberService) {
        this.memberService = memberService;
    }
}

This delays MemberService bean creation until actually used, resolving the circular reference error.

---

Mentor Feedback

“@Lazy only postpones the problem. The design issue of circular dependencies still exists. Over time, adding new features becomes harder due to the tangled dependencies.”

---

Root Cause

The problem was that MemberService and WishlistService both depended on each other.

MemberService: getMemberWithWishlist() → needs WishlistService
WishlistService: getWishlistWithMember() → needs MemberService

---

Real Solution: Rethink the Design

1. Extract common logic: Move shared logic to a new service
2. Use DTOs for data transfer: Don’t pass entire service, pass only needed data
3. Apply Facade pattern: Create a coordinating service for cross-service operations

// Before: MemberService directly calls WishlistService
// After: MemberWishlistFacade coordinates both
@Service
public class MemberWishlistFacade {
    private final MemberService memberService;
    private final WishlistService wishlistService;

    public MemberWithWishlistDto getMemberWithWishlist(Long memberId) {
        Member member = memberService.findById(memberId);
        List<WishlistItem> wishlist = wishlistService.findByMemberId(memberId);
        return new MemberWithWishlistDto(member, wishlist);
    }
}

---

Lessons Learned

• @Lazy is a workaround, not a solution
• Circular dependencies indicate design problems
• When they occur, reconsider responsibility distribution
• Proper layering is important

---

From Kakao Tech Campus 3rd cohort Gift API clone coding, summarizing mentor feedback.

• spring-gift-wishlist