I’m working with JPA in my project and I keep seeing these two fetch types mentioned everywhere. Can someone explain what happens when you use EAGER loading compared to LAZY loading? I understand they control when data gets loaded from the database but I’m not sure about the practical differences. For example, if I have an entity with relationships, how does each fetch type behave differently? When should I choose one over the other? I’ve been using the default settings but I think I need to understand this better to optimize my application’s performance. Any examples or explanations would be really helpful.
I’ve worked with JPA apps for a while, and EAGER vs LAZY choice really matters with big datasets. EAGER loading seems fine when you’re testing with small data, but it’ll kill your performance once you hit production with thousands of records. The N+1 problem gets brutal - JPA starts firing separate queries for each related entity instead of smart joins. LAZY gives you control but you’ve got to manage sessions carefully. I skip annotation defaults and use entity graphs or explicit fetch strategies in repository methods instead. You can customize loading per use case rather than forcing everything into one approach. Also, Hibernate’s batch fetching helps optimize LAZY loading by cutting down database round trips when you need multiple lazy relationships.
eager loads everything at once, which can slow things down if you dont need it all. lazy loads only what you need, but sometimes can run into issues when sessions close too fast. usually go for lazy unless i’m sure i need associated data right away.
I’ve dealt with this performance issue plenty of times. EAGER vs LAZY really depends on how you’re accessing your data. EAGER runs joins right away when you grab the parent entity - one query gets everything. Great if you know you’ll need that data, but it’ll bite you with deep object graphs since you end up loading tons of records you don’t actually use. LAZY only fires queries when you actually touch the relationship properties. The gotcha? LazyInitializationException when your session closes before you access the lazy property. I’ve been burned by this in web apps where the session dies before the view renders. My approach: default to LAZY, then switch to EAGER only for relationships I always need. You can also use fetch joins in JPQL to override the default when it makes sense.