Arrays are a common data type in Java and part of the SQL-99 standard. So, it should be easy and quite common to use them with Hibernate, right? No, they aren’t. Most developers try to avoid using arrays in their persistence layers. There are several reasons for that: Not all DBMS support arrays. Because of…
When you model a hierarchical data structure, you often have to use self-referencing associations. Both ends of these associations are of the same type. In other words, the entity object on which the association is defined and the one the association references are of the same type. In your database, you model that using a…
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…
