Why JPA Buddy complains about @Data annotation over JPA Entity?

Question

I discovered JPA Buddy plugin for IntelliJ IDEA. In all my projects i love to use Lombok. It saves a lot of space in my entity classes. However, i just noticed, that JPA Buddy highliths it and suggest to replace.

E.g.:

As a result, the @Data annotation is replaced with:

@Getter
@Setter
@ToString
@RequiredArgsConstructor

the hashCode and equals implementations were added:

@Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || Hibernate.getClass(this) != Hibernate.getClass(o)) {
            return false;
        }
        Project project = (Project) o;
        return id != null && Objects.equals(id, project.id);
    }

    @Override
    public int hashCode() {
        return getClass().hashCode();
    }

I clearly see the desription: Using @Data for JPA entities is not recommended. It can cause severe performance and memory consumption issues

But can somebody provide some real world example? From my perspective, @Data includes everything i need (equals/hashcode) as well. And i didn't notice any performance issues in my projects.

(mini rant) Hibernate/JPA is a complicated technology, it's important that one knows its caveats before using it. I often see teams using hibernate (and spring-jpa) with little idea of how it works and this causes all kinds of unexpected errors (and workaround hacks, which makes the code hard to read). I would *strongly* suggest you to get a book that explains the basics (maybe `Java Persistence with Hibernate`) — Augusto, Jan 20 '23 at 09:52

score 6 · Accepted Answer · answered Jan 20 '23 at 10:30

JPA Buddy follows best practices, and @Data for JPA entities is an antipattern... You can read more here (with some real-world examples): https://www.jpa-buddy.com/blog/lombok-and-jpa-what-may-go-wrong/.

In short:

According to the JPA specification, all entity classes are required to have a public or protected no-argument constructor. @Data includes only @AllArgsConstructor and not @NoArgsConstructor
You can easily load attributes that are marked as Lazy due to the default @ToString method implementation provided by Lombok – which can significantly reduce the performance of your app.
Finally, @EqualsAndHashCode implementation can break HashSets (and HashMaps) behavior under certain conditions.

score 3 · Answer 2 · answered Jan 20 '23 at 09:39

3

Have a look at this blog post, it explains what could go wrong with Lombok's generated equals() and hashCode() inside JPA entity classes and why it should be avoided

answered Jan 20 '23 at 09:39

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Why JPA Buddy complains about @Data annotation over JPA Entity?

2 Answers2