How to persist @ManyToMany relation - duplicate entry or detached entity

Question

I want to persist my entity with ManyToMany relation. But i have some problem during persisting process.

My entities :

@Entity
@Table(name = "USER")
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long userId;

    @Column(name = "NAME", unique = true, nullable = false)
    String userName;

    @Column(name = "FORNAME")
    String userForname;

    @Column(name = "EMAIL")
    String userEmail;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name = "USER_USER_ROLES", joinColumns = @JoinColumn(name = "ID_USER"), inverseJoinColumns = @JoinColumn(name = "ID_ROLE"))
    List<UserRoles> userRoles = new ArrayList<UserRoles>();

    // getter et setter
}

and

@Entity
@Table(name = "USER_ROLES")
public class UserRoles implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long userRolesId;

    @Column(unique = true, nullable = false, name = "ROLE_NAME")
    String roleName; 

    // getter et setter
}

Service code :

User user = new User();
UserRoles role;
try {
    role = userRolesServices.getUserRoleByName("ROLE_USER"); // find jpql - transaction
} catch (RuntimeException e) {
    LOGGER.debug("No Roles found");
    role = new UserRoles("ROLE_USER"); // create new
}
user.addUserRole(role);
user.setUserName(urlId);
user.setUserForname(fullName);
user.setUserEmail(email);
userServices.createUser(user); // em.persist(user) - transaction

First time, when I try to persist a User with UserRoles "ROLE_USER", no problem. User and UserRoles and join tables are inserted.

My problem is when I try to persist a second User with the same UserRoles. I check if the UserRoles exists by finding it (userRolesServices.getUserRoleByName(...)). If exists -> add this UserRoles to User list (id + role name) else i create a new one (only role name).

By when I try to persist the second User, i obtain the following exception : "detached entity to persist : .....UserRoles" (maybe because getUserRoleByName is performed in another transaction)

If I do not use getUserRoleByName (only *new UserRoles("ROLE_USER");*), i obtain the following exception : "...ConstraintViolation : Duplicated entry for 'ROLE_NAME' ..."

So, how to properly persist an entity with @ManyToMany relation ?

score 30 · Accepted Answer · edited May 17 '17 at 16:27

30

For above problem I would say your entity relationship cascade is wrong. Consider this: A user can have multiple roles but there can be fixed number of roles that can exist in the system. So CASCADE ALL from User entity does not make any sense, since life cycle of UserRoles should not depend on User entity life cycle. E.g. when we remove User, UserRoles should not get removed.

detached entity to persist exception will only occur when you are passing object which has primary key already set to persist.

Remove cascade and your problem will be solved now only thing you will need to decide is how you are going to insert User roles. According to me there should be separate functionality to do so.

Also do not use ArrayList, use HashSet. ArrayList allows duplicates.

edited May 17 '17 at 16:27

naXa stands with Ukraine

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answered Mar 24 '12 at 10:50

Amit Deshpande

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1

I can delete REMOVE from cascade type : cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH} ? But I think I always obtain "unique constraint violation" on persist...(with no id)... And if I remove cascade and persist UserRoles manually, how can I modify the join table ? And what is the utility of a this relationship ? Ok for HashSet, i will modify it... – Aure77 Mar 26 '12 at 08:10
1

Using cascade = CascadeType.MERGE works ! thanks for you're help. – Aure77 Mar 28 '12 at 11:55
1

@Aure77, I've the same problem as you. I can set cascade to MERGE, but then UserRoles won't be created anymore when they are new... and I'll get a constraint violation when hibernate tries to insert into the join table referencing a non existent row on the user roles table. So, did I miss something? Thanks! – user683887 Sep 28 '12 at 18:31
I've removed cascade and my problem is solved, just as you said! – naXa stands with Ukraine May 17 '17 at 16:28

score 12 · Answer 2 · answered Mar 30 '16 at 15:13

I will provide my answer if anyone get same type of problem to me and the author.

Basically what I was facing was a situation when I had one table which was some kind of CONSTANT values. And the other would change, but it should map (many to many) to those CONSTANTS.

The exact problem is USERS and it's ROLES.

Roles would be known and added on system startup, thus they should never get removed. Even if no user would have some Role it should still be in the system.

The class implementation, using JPA:

User:

@Entity
@Table(name = "USERS")
public class User{

    @Id
    private String login;
    private String name;
    private String password;

    @ManyToMany(cascade = {CascadeType.MERGE})
    private Set<Role> roles = new HashSet<>();

Role:

@Entity
@Table(name = "ROLE")
public class Role {

    @Id
    @Enumerated(value = EnumType.STRING)
    private RoleEnum name;

    @ManyToMany(mappedBy = "roles")
    private Set<User> users = new HashSet<>();

Usage

This setup will easily add/remove Role to User. Simply by passing an array, f.e.: user.getRoles().add(new Role("ADMIN")); and merge the user. Removing works with passing an empty list.

If you forget to add the Role before adding it to the user most likely you will get an error like:

javax.persistence.RollbackException: java.lang.IllegalStateException: During synchronization a new object was found through a relationship that was not marked cascade PERSIST: com.storage.entities.Role@246de37e.

What and why

mappedBy attribute is added to the child Entity as described in the JPA Docs

If you choose to map the relationship in both directions, then one direction must be defined as the owner and the other must use the mappedBy attribute to define its mapping (...)

cascade = {CascadeType.MERGE} is added for proper cascades JPA Docs

Cascaded the EntityManager.merge() operation. If merge() is called on the parent, then the child will also be merged. This should normally be used for dependent relationships. Note that this only affects the cascading of the merge, the relationship reference itself will always be merged.

ATUL ANAND · Answer 3 · 2020-06-11T20:48:16.273

Duplication Reason: Id is autogenerated, so every time a new role is being created. Use in this way :

User

@Entity
@Table(name = "user")
public class User {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int user_Id;

@Column(name = "email")
private String email;

@Column(name = "firstname")
private String firstname; 

@Column(name = "lastname")
private String lastname;

@Column(name = "password")
private String password;

@Column(name = "active")
private int active;

@ManyToMany(cascade = CascadeType.MERGE, fetch = FetchType.EAGER)
@JoinTable(name="user_role", 
    joinColumns=@JoinColumn(name="user_Id"),
    inverseJoinColumns=@JoinColumn(name="role_Id"))
private Set<Role> roles  = new HashSet<>();
//Getter and Setter

Role

@Entity
@Table(name="roles")
public class Role {

 @Id
 @Column(name="role_Id")
 private int role_Id;

 @Column(name="role_name")
 private String role_name;

 @ManyToMany(mappedBy = "roles")
 private Set<User> users= new HashSet<>();

Controller (Should have added it to Service)

 @PutMapping("/addEmp")
   public String addEmp(@RequestBody User user) {

    String pass=passencoder.encode(user.getPassword());
    user.setPassword(pass);
    List<Role> roles =rolerepo.findAll();
    for(Role role: roles) 
        System.out.println("Roles"+ role.getRole_name());
    //user.setRoles(new HashSet < > (rolerepo.findAll()));
    userrepo.save(user);


    return "User Created";
}

Output

Roles

User_Role

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score 0 · Answer 4 · edited Jul 12 '20 at 12:45

I have the same issue, but couldn't get through it yet. My RelationShip is Hotel to DeliveryPartners. Following are the classes:

@Entity Class 

package com.hotelapp.models;

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.*;
import java.util.Set;

@Entity
@Getter
@Setter
@NoArgsConstructor
public class Hotel {

    @Id
    @GeneratedValue(generator = "hotel_id", strategy = GenerationType.AUTO)
    @SequenceGenerator(name = "hotel_id", sequenceName = "hotel_id")
    private Integer hotelId;
    private String hotelName;
    @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "address_id")
    private Address address;
    @OneToMany(cascade =  CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "hotel_id")
    private Set<Menu> menuList;
    @ManyToMany(cascade = {CascadeType.MERGE} ,fetch = FetchType.EAGER)
    @JoinTable(name ="hotel_delivery", joinColumns = @JoinColumn(name ="hotel_id"), inverseJoinColumns = @JoinColumn(name="delivery_id"))
    private Set<Delivery> delivery;

    public Hotel(String hotelName, Address address, Set<Menu> menu, Set<Delivery> delivery) {
        this.hotelName = hotelName;
        this.address = address;
        this.menuList = menu;
        this.delivery = delivery;
    }

    @Override
    public String toString() {
        return "Hotel{" +
                "hotelName='" + hotelName + '\'' +
                ", address=" + address +
                ", menu=" + menuList +
                ", delivery=" + delivery +
                '}';
    }
}

@Delivery Class

package com.hotelapp.models;

import com.fasterxml.jackson.annotation.JsonIgnore;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Getter
@Setter
@NoArgsConstructor
public class Delivery {

    @Id
    @GeneratedValue(generator = "del_id", strategy = GenerationType.AUTO)
    @SequenceGenerator(name = "del_id", sequenceName = "delivery_id")
    private Integer deliveryId;
    private String partnersName;
    private Double charges;
    @ManyToMany(mappedBy = "delivery", cascade = CascadeType.MERGE, fetch = FetchType.EAGER)
    @JsonIgnore
    private Set<Hotel> hotelList = new HashSet<>();

    public Delivery(String partnersName, Double charges) {
        this.partnersName = partnersName;
        this.charges = charges;
    }

    @Override
    public String toString() {
        return "Delivery{" +
                "partnersName='" + partnersName + '\'' +
                ", charges='" + charges + '\'' +
                '}';
    }
}

@Controller Class

  @PostMapping("/hotels")
    public ResponseEntity<Hotel> addHotel(@RequestBody Hotel hotel){
        Hotel hotel1 =hotelService.addHotel(hotel);
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.add("desc", "oneHotelAdded");
        return ResponseEntity.ok().headers(httpHeaders).body(hotel1);
    }

When I use merge cascade type, getting following exception:

Hibernate: insert into address (city, state, street_name, zip_code, address_id) values (?, ?, ?, ?, ?)
Hibernate: insert into hotel (address_id, hotel_name, hotel_id) values (?, ?, ?)
Hibernate: insert into menu (hotel_id, menu_name, price, menu_id) values (?, ?, ?, ?)
Hibernate: insert into menu (hotel_id, menu_name, price, menu_id) values (?, ?, ?, ?)
Hibernate: insert into menu (hotel_id, menu_name, price, menu_id) values (?, ?, ?, ?)
Hibernate: insert into hotel_delivery (hotel_id, delivery_id) values (?, ?)
2020-07-12 00:13:37.973 INFO 50692 --- [nio-9098-exec-1] o.h.e.j.b.internal.AbstractBatchImpl : HHH000010: On release of batch it still contained JDBC statements
2020-07-12 00:13:38.026 ERROR 50692 --- [nio-9098-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientObjectException: object references an unsaved transient instance - **save the transient instance before flushing: com.hotelapp.models.Delivery; nested exception is java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.hotelapp.models.Delivery] with root cause
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.hotelapp.models.Delivery**
at org.hibernate.engine.internal.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:347) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:495) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.type.EntityType.nullSafeSet(EntityType.java:280) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.persister.collection.AbstractCollectionPersister.writeElement(AbstractCollectionPersister.java:930) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1352) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.action.internal.CollectionRecreateAction.execute(CollectionRecreateAction.java:52) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:478) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at java.util.LinkedHashMap.forEach(LinkedHashMap.java:684) ~[na:1.8.0_221]
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:475) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:348) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:40) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102) ~[hibernate-core-5.4.17.Final.jar:5.4.17.Final]

I realise from the queries part there is no insert query for delivery table so that delivery can be used in hotel_delivery (MTM Table). Don't know how to proceed now.

score 0 · Answer 5 · answered Jun 24 '21 at 20:45

I was getting the same error, but after adding the cascade = CascadeType.ALL for both sides of relationship the issue is resolved. earlier I was cascade = CascadeType.ALL only on the parent side of the relation, after adding child also the code is working fine now. here is my code.

Reader(parent entity):

  @ManyToMany(cascade = CascadeType.PERSIST)
        @JoinTable(name="READER_SUBSCRIPTIONS", joinColumns= 
         {@JoinColumn(referencedColumnName="ID")}
            , inverseJoinColumns={@JoinColumn(referencedColumnName="ID")})
  private List<Subscription> subscriptions;

Subscription (child entity):

  @ManyToMany(mappedBy="subscriptions", cascade = CascadeType.ALL)
  private Set<Reader> readers;

Persistence code:

List<Subscription> list = new ArrayList<Subscription>();
list.add(sub1);
list.add(sub2);

Set<Reader> readerSet = new HashSet<Reader>();
readerSet.add(reader1);
readerSet.add(reader2);

reader1.setSubscriptions(list);
reader1.setSubscriptions(list);

sub1.setReaders(readerSet);
sub2.setReaders(readerSet);

reader2.setSubscriptions(list);
reader2.setSubscriptions(list);

readSubscriberRepository.save(reader1);
readSubscriberRepository.save(reader2);

score 0 · Answer 6 · answered Mar 22 '12 at 12:46

0

(maybe because getUserRoleByName is performed in another transaction)

That would seem to the the issue, do the query in the same transaction/entity manager. Otherwise re-find it in the current transaction using find().

answered Mar 22 '12 at 12:46

James

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I have 2 services : UserServices and UserRolesServices. Each one have get (find) method in a transaction (spring @Transactional). So, if i call UserRolesServices find method in UserService persist method, should it performed in same transaction ? – Aure77 Mar 22 '12 at 12:50
Tested and doesn't work as expected... because each service has is own transaction (i think)...Always "detached entity to persist" – Aure77 Mar 22 '12 at 22:15

How to persist @ManyToMany relation - duplicate entry or detached entity

6 Answers6

The class implementation, using JPA:

Usage

What and why

Linked