Hibernate - @ElementCollection - Strange delete/insert behavior

user_447348 0
Viewed 46011
@Entity
public class Person {

    @ElementCollection
    @CollectionTable(name = "PERSON_LOCATIONS", joinColumns = @JoinColumn(name = "PERSON_ID"))
    private List<Location> locations;

    [...]

}

@Embeddable
public class Location {

    [...]

}

Given the following class structure, when I try to add a new location to the list of Person's Locations, it always results in the following SQL queries:

DELETE FROM PERSON_LOCATIONS WHERE PERSON_ID = :idOfPerson

And

A lotsa' inserts into the PERSON_LOCATIONS table

Hibernate (3.5.x / JPA 2) deletes all associated records for the given Person and re-inserts all previous records, plus the new one.

I had the idea that the equals/hashcode method on Location would solve the problem, but it didn't change anything.

Any hints are appreciated!

jpa-2.0 jpa orm hibernate java
4 Answers

We discovered that entities we were defining as our ElementCollection types did not have an equals or hashcode method defined and had nullable fields. We provided those (via @lombok for what it's worth) on the entity type and it allowed hibernate (v 5.2.14) to identify that the collection was or was not dirty.

Additionally, this error manifested for us because we were within a service method that was marked with the annotation @Transaction(readonly = true). Since hibernate would attempt to clear the related element collection and insert it all over again, the transaction would fail when being flushed and things were breaking with this very difficult to trace message:

HHH000346: Error during managed flush [Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1]

Here is an example of our entity model that had the error

@Entity
public class Entity1 {
@ElementCollection @Default private Set<Entity2> relatedEntity2s = Sets.newHashSet();
}

public class Entity2 {
  private UUID someUUID;
}

Changing it to this

@Entity
public class Entity1 {
@ElementCollection @Default private Set<Entity2> relatedEntity2s = Sets.newHashSet();
}

@EqualsAndHashCode
public class Entity2 {
  @Column(nullable = false)
  private UUID someUUID;
}

Fixed our issue. Good luck.

user_2113330

I had the same issue but wanted to map a list of enums: List<EnumType>.

I got it working like this:

@ElementCollection
@CollectionTable(
        name = "enum_table",
        joinColumns = @JoinColumn(name = "some_id")
)
@OrderColumn
@Enumerated(EnumType.STRING)
private List<EnumType> enumTypeList = new ArrayList<>();

public void setEnumList(List<EnumType> newEnumList) {
    this.enumTypeList.clear();
    this.enumTypeList.addAll(newEnumList);
}

The issue with me was that the List object was always replaced using the default setter and therefore hibernate treated it as a completely "new" object although the enums did not change.

user_36368220
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