java.lang.IllegalStateException: Multiple representations of the same entity with @ManyToMany 3 entities

问题

I have 3 entities with ManyToMany relationships:

Role Entity:

@Entity
public class Role {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer roleID;
    private String roleName;
    private String description;

    @ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH}, fetch = FetchType.EAGER)
    @JoinTable(name = \"role_permission\", joinColumns = {@JoinColumn(name = \"role_id\")}, inverseJoinColumns = {@JoinColumn(name = \"permission_id\")})
    private Set<Permission> permissions = new LinkedHashSet<Permission>();
}

Permission Entity:

@Entity
public class Permission {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int permissionID;
    private String permissionName;
    private String description;

    @ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH}, fetch = FetchType.EAGER)
    @JoinTable(name = \"permission_functionality\", joinColumns = {@JoinColumn(name = \"permission_id\")}, inverseJoinColumns = {@JoinColumn(name = \"functionality_id\")})
    private Set<Functionality> functionalities = new LinkedHashSet<>();
}

Functionality Entity:

@Entity
public class Functionality {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
}

I did the following:

1. I have created 3 functionalities:

   Functionality1, Functionality2, Functionality3
   

2. Then created 2 permissions:

   Permission1 with Functionality1, Functionality2
   
   Permission2 with Functionality2, Functionality3
   

3. Then created a role:

   Role1 with Permission1 and Permission2 
   

I am getting the following exception:

java.lang.IllegalStateException: Multiple representations of the same entity [com.persistence.entity.admin.Functionality#1] are being merged. Detached: [com.persistence.entity.admin.Functionality@4729256a]; Detached: [com.persistence.entity.admin.Functionality@56ed25db]

回答1:

Fixed it by removing CascadeType.MERGE on Permission entity

回答2:

The correct solution would have been to upgrade to hibernate 4.2.15 / 4.3.6 or above and add the following lines to your persistence.xml:

<property name="hibernate.event.merge.entity_copy_observer" value="allow"/>

回答3:

Check your equals and hashCode method, ensure that it is consistent and correctly defined. For example I had copied and mistakenly pasted another-class when computing hashCode, this caused the object never to be equal with itself :(.

回答4:

I ran into the same problem too and solved it by add a few configs in application.yaml files.

  jpa:
    properties:
      hibernate:
        enable_lazy_load_no_trans: true
        event:
          merge:
            entity_copy_observer: allow

See it here How to persist a new entity containing multiple identical instances of another unpersisted entity with spring-boot and JPA?

回答5:

In my case, moving the fetch operation and save operation in same @Transactional block solved the problem.

回答6:

error occurs when we have multiple object of same time in HashSet.Possible due to incorrect hash function.Hashset check equality of object on the basis of hash function between two objects.

Way to debug

Just try to print hashset you will see multiple object of same type.

Solution::#

• Use HashSet while defining one to many relationships.
• Avoid using Lists.
• Make sure your hash function should be correct.

回答7:

@LazyCollection(LazyCollectionOption.FALSE

@OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)

@JoinColumn(name = "translate_id")

回答8:

I could fix it by replacing

cascade = CascadeType.All

with

casecade={CascadeType.PERSIST,CascadeType.REMOVE}

回答9:

For Hibernate see the workaround here HHH-9106.

回答10:

Just a note to say I am using Hibernate Core 4.3.8 in a Spring MVC application, based on Spring Core 4.1.6. The workaround:

<property name="hibernate.event.merge.entity_copy_observer" value="allow"/>

Did not work for me. I needed to remove the CascadeType.MERGE in order to correctly populate an @ManyToMany. Not sure if newer versions of Hibernate have fixed this.

来源：https://stackoverflow.com/questions/26591521/java-lang-illegalstateexception-multiple-representations-of-the-same-entity-wit