What are the most common pitfalls with JPA/Hibernate and @Transactional?
Answer
- N+1 queries: LAZY collections accessed in a loop; fix with
join fetch, @EntityGraph, batch size or DTO projections. LazyInitializationException: reading a lazy field outside the transaction; fetch what you need inside the service or use DTOs.- Self-invocation or private methods: proxy bypassed, so no transaction.
- Checked exceptions do not roll back by default (
rollbackFor). - Too-long transactions (calling slow HTTP services inside) hold database connections.
- Returning entities directly from controllers: leaks fields and triggers lazy loading.
open-in-view (default true in Boot) hides lazy loading problems in the web layer; many teams disable it.
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