JPA Hibernate: An entity copy [xxx] was already assigned to a different entity [yyyyy]

Question

Recently, when I use JPA(1.3.0.final) and Hibernate(4.2.6.final) on Play 2.2.1 framework, I got errors like:

java.lang.IllegalStateException: Error occurred while storing entity [xxx] An entity copy [xxx] was already assigned to a different entity [yyy]

And none of the existing solutions on the Internet solves my prbolem.

Now, let me explain a bit about the story.

I have three entities, Owner, Box, and Item.

Assumptions:

1. An Item or a Box must have an Owner;
2. A Box may contain zero or more Items, while an specific Item may not belong to any Box.
3. When an Item is put into a Box, they may or may not have the same Owner.

Entity Class:

/* for simplicity, others fields, getter and setter are ommitted*/

The simplified Owner class definition

    @Entity
    @Table(name = "OWNER")
    public class Owner implements Serializable{
        @Id
        @Column(name="ID")
        public String uuid = UUID.randomUUID().toString();

        @Override
        public int hashCode() {
            int result = 1;
            char[] charArray = this.uuid.toCharArray();
            int n = charArray.length;
            int powbase = (int) Math.pow(31, n - 1);
            for(int i = 0; i < n; i++){
                if ( i != 0){
                powbase = powbase / 31;
                }
                result += (int)charArray[i] * powbase;
            }
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if(obj == null){
                return false;
            }
            if(!(obj instanceof Item)){
                return false;
            }
            Item other = (Item)obj;
            //Box other = (Box)obj;
            //Owner other = (Owner)obj;
            if(!other.uuid.equals(this.uuid)){
                return false;
            }
            return true;
        }
}

The implementation of hashCode() and equals() of Item and Box are similar to Owner. For sake of argument, let's omit these.

The simplified Item class definition

@Entity
@Table(name = "ITEM")
public class Item implements Serializable{

    @Id
    @Column(name="ID")
    public String uuid = UUID.randomUUID().toString();

    /* single-directional mapping*/
    @ManyToOne(cascade = { CascadeType.MERGE, CascadeType.REFRESH }, optional = false)
    @JoinColumn(name = "O_ID")
    public Owner owner;

    /* bi-directional mapping*/
    @ManyToOne(cascade = { CascadeType.MERGE, CascadeType.REFRESH })
    @JoinColumn(name = "B_ID")
    public Box box;
}

The simplified Box class definition.

@Entity
@Table(name = "BOX")
public class Box implements Serializable {

    @Id
    @Column(name="ID")
    public String uuid = UUID.randomUUID().toString();

    /* single-directional mapping*/
    @ManyToOne(cascade = { CascadeType.MERGE, CascadeType.REFRESH }, optional = false)
    @JoinColumn(name = "O_ID")
    public Owner owner;

    /* bi-directional mapping*/
    @OneToMany(cascade = { CascadeType.PERSIST, CascadeType.REFRESH,
            CascadeType.MERGE, CascadeType.REMOVE }, fetch = FetchType.EAGER, mappedBy = "box")
    public Set<Item> items = new HashSet<Item>();
}

The business logic is shown as follows:

public class Test {

    public static void main(String[] args) {
        Owner owner = new Owner();
        JPA.em().persist(owner);

        Box box = new Box();
        box.owner = owner;
        JPA.em().persist(box);

        Item boxItem = new Item();
        boxItem.owner = owner;
        boxItem.box = box;
        box.items.add(boxItem);
        JPA.em().persist(boxItem);

        Item nonBoxItem = new Item();
        nonBoxItem.owner = owner;
        JPA.em().persist(nonBoxItem);

        /* in the future, put the 'nonBoxItem' into a box*/
        Item itemToUpdate = JPA.em().find(Item.class, nonBoxItem.uuid);
        itemToUpdate.box = box;
        box.items.add(itemToUpdate);

        JPA.em().merge(itemToUpdate); /* error occurred here*/
    }

}

Does anyone have any idea to solve this problem?

Thanks.

Answer 1

I had the same problem. solved by adding dependency from this link https://stackoverflow.com/questions/17634230/hibernate-an-entity-copy-was-already-assigned-to-a-different-entity that worked for me

<dependency>
<groupId>com.intersult</groupId>
<artifactId>jpa-fix</artifactId>
<version>1.1</version>

Cheers!