Overview When it comes to data integrity, the famous example that people usually mention is the bank transfer scenario: Alice sends money to Bob, and Bob sends money to Alice. I also read that using @Transactional is the solution for such cases. However, is using @Transactional annotation enough to make Alice and Bob happy? Let’s … Read more
Overview When working with spring data jpa, you probably come across issues like this: You have an entity with an @Embedded attribute. The @Embeddable class has the one property that has the same name as one of your entities’. You got this error when running the program: What do you do? Why Do you have … Read more
Overview @ManyToOne and @OneToMany are standard mappings in Hibernate. Understanding how to use them correctly is the key to mapping entities efficiently in Hibernate. In this post, I will show you how to use these annotations and give examples to demonstrate use cases. The analogy I use is schools and students. In real life, schools … Read more
Overview Imagine this scenario, you have a legacy database that store weather data. The previous developer, due to various reason, store the temperature in the following format: id location temperature capture_date 1 Hanoi 30.50 C 2023-07-31 22:10:30.000 2 New York 95.20 F 2023-07-31 22:10:30.000 As you can see, the temperature stored in a sub-optimal way … Read more
Overview One of the lesser-known yet powerful annotations in Hibernate is @ColumnTransformer. This annotation let us apply SQL transformations on entity properties when interacting with the database. You can think of this annotation as a two way converter. A real life use case Let’s consider a weather app that initially use Kelvin scale to store … Read more
Overview From the official documentation, a Formula mapping defines a “derived” attribute (that means, not persisted), whose state is determined from other columns and functions when an entity is read from the database. You’d probably know other annotation that make a field not persisted to the database: @Transient. While they both allow you to create … Read more