Question
Why am I encountering the HibernateException: Found shared references to a collection while trying to manage related entities in Hibernate?
person.addToRelatedPersons(anotherPerson);
anotherPerson.addToRelatedPersons(person);
anotherPerson.save();
person.save();
Answer
The HibernateException: Found shared references to a collection typically occurs when Hibernate detects that one or more entities reference a shared collection. This scenario primarily arises in bidirectional relationships where both sides of the relationship attempt to manage the same collection. In your case, the error points to the shared references between two 'Person' entities.
@Entity
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@ManyToMany(cascade = CascadeType.ALL)
private Set<Person> relatedPersons = new HashSet<>();
public void addToRelatedPersons(Person person) {
this.relatedPersons.add(person);
person.getRelatedPersons().add(this);
}
public Set<Person> getRelatedPersons() {
return relatedPersons;
}
}
Causes
- Both entities are trying to add each other into a shared collection without proper lifecycle management.
- Hibernate does not support recursive references without correctly defined relationships in its configuration.
- Modification of collections should be managed carefully to ensure that Hibernate can track changes.
Solutions
- Ensure that the adding/removing of related objects is managed through one side of the relationship, usually the owning side.
- Consider using methods that manage both sides of the relationship (one entity at a time) by calling a method on one side, thus maintaining control over the relationship.
- Use @Transactional annotations if you are performing database operations within a transactional context to prevent state inconsistencies.
Common Mistakes
Mistake: Not managing both sides of the relationship correctly.
Solution: Use a dedicated method to manage both sides properly to avoid shared references.
Mistake: Calling `save()` methods without ensuring transaction management.
Solution: Always wrap database operations within a transaction to ensure consistency.
Helpers
- HibernateException
- shared references collection error
- Hibernate collection management
- bidirectional relationships Hibernate
- Hibernate save method errors