How to map a JPA @ManyToOne relationship to a SQL query using the Hibernate @JoinFormula annotation

Introduction

Someone asked me to answer the following StackOverflow question, and, because the question is very interesting from an SQL perspective, I decided to turn the answer it into a blog post.

In this article, we are going to see how to map a JPA @ManyToOne association to the result of a SQL query using the Hibernate-specific @JoinFormula annotation.

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How to audit entity modifications using the JPA @EntityListeners, @Embedded, and @Embeddable annotations

Introduction

After I wrote the article about inheriting properties from a base class entity using @MappedSuperclass, I got an avalanche of opinions, but this one from Lukas deserves a blog post:

While @MappedSuperclass has its benefit, allowing you to reuse even the @Id mapping, as well as being more lenient towards Hibernate-specific auto-generated properties like @GeneratedValue, using Embeddable types is the other JPA alternative for reusing a bunch of properties among multiple entities.

In this article, we are going to see how we can reuse several audit-related properties using @Embeddable and another awesome JPA feature, @EntityListeners.

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How to emulate @CreatedBy and @LastModifiedBy from Spring Data using the @GeneratorType Hibernate annotation

Introduction

Hibernate comes with many additions to the standard JPA specification. One such example is the @GeneratorType annotation which allows you to customize the way a given entity property value is automatically generated.

If you’re using Spring Data, you can simply use the @CreatedBy and @LastModifiedBy annotations and the annotated entity properties are going to be populated with the currently logged user.

If you’re not using Spring Data, then you can easily emulate the same behavior using the Hibernate-specific @GeneratorType annotation and the ValueGenerator callback mechanism.

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The best way to map a @NaturalId business key with JPA and Hibernate

Introduction

As I explained in this free chapter of my book, Hibernate offers many benefits over standard JPA. One such example is the @NaturalId mapping.

In this article, you are going to see what is the best way to map a natural business key when using Hibernate.

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How does Hibernate handle JPA Criteria API literals

Introduction

The JPA specification is like a Java interface, However, when it comes to performance, implementation details matter a lot. That’s why, even if you use the JPA standard, you still need to know how the underlying provider implements the standard specification.

For instance, if we take this tweet from Gareth Western:

We can clearly see that there is an issue in the way literals might be handled by Hibernate when executing a Criteria API query.

Therefore, in this article, we are going to see how literals are handled by Hibernate and explain what we have changed in Hibernate 5.2.12.

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