The entity lifecycle model is one of the core concepts of JPA and all its implementations. Even though it’s not directly visible when working with JPA’s EntityManager, it affects all operations you perform. The different states of the model define how your persistence provider, e.g. Hibernate, handles your entity objects. This includes if it loads
An association between 3 entities is called a ternary association. A typical example is an association between an employee, the project they are working on, and their role in that project. If the role is a complex object, you might decide to model this as 3 entity classes. The association between them is the interesting
Every framework has a set of exceptions that indicate common error scenarios. Understanding them will help you turn a task that could drag along for days into a quickly-implemented feature. When working with Hibernate, they tell you about issues with your database queries, mapping mistakes, and problems during write operations. In this article, I want
Projection is one of the first things you’re probably thinking about when implementing a query with Spring Data JPA. This is because projection defines the entity attributes and the database columns returned by your query. So, selecting the right columns is important for your business logic. At the same time, projection is also crucial for
Using JPA’s and Hibernate’s 2nd level cache can improve the performance of your persistence layer. It acts as a session-independent entity store. Hibernate uses it whenever you call the find method on your EntityManager or traverse an association to fetch a cached entity. Instead of executing a database query, Hibernate gets the entity object from
Lombok is a popular framework among Java developers because it generates repetitive boilerplate code like getter and setter methods, equals and hashCode methods, and the default constructor. All you need to do is add a few annotations to your class and Lombok will add the required code at compile time. This works reasonably well for
All applications that get deployed to production should use an automated approach to migrate their database. It makes your job a lot easier. It also ensures you don’t miss any changes during the update process. That’s, of course, also true if you develop your application based on Spring Boot. The integration of Flyway and Liquibase
JPA and Hibernate require you to write lots of Strings. You use them to create ad-hoc and named queries with JPQL, to define native SQL queries and to specify the fetching behavior in an EntityGraph. Until Java 13, the lack of multiline Strings in Java made all of these tasks either annoying to implement or
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