Choosing the right FetchType is one of the most important decisions when defining your entity mapping. It specifies when your JPA implementation, e.g., Hibernate, fetches associated entities from the database. You can choose between EAGER and LAZY loading. The first one fetches an association immediately, and the other only when you use it. I explain…
When we’re talking about performance optimizations for Spring Data JPA, the handling of associations is always an important topic. Because Spring Data JPA is based on JPA and most often used with Hibernate, you can apply all the performance tuning concepts you can find here on the blog. The most important one is to use…
You probably learned that you should use FetchType.LAZY for all of your associations. It ensures that Hibernate initializes an association when you use it and doesn’t spend any time getting data you don’t need. Unfortunately, this introduces a new issue. You now need to use a JOIN FETCH clause or an EntityGraph to fetch the…
EntityGraphs and JOIN FETCH clauses provide an easy and efficient way to fetch an entity and initialize its associations. But if you try to use it with a domain model that uses inheritance, you will quickly run into an issue: You can’t use this approach in a polymorphic query to fetch an association that’s defined…
The LazyInitializationException is one of the most common exceptions when working with Hibernate. There are a few easy ways to fix it. But unfortunately, you can also find lots of bad advice online. The proclaimed fixes often replace the exception with a hidden problem that will cause trouble in production. Some of them introduce performance…
