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JPA cascading delete fails with custom delete method

I ran into an error with custom delete method in spring data jpa. Basically there's a bag which contains items, and when deleting the bag, all the items in it should be deleted.
Here're the entities:
#Entity
#Table(name = "bag")
public class Bag {
#Id private Long id;
#Column("uid") private Long uid;
#Column("name") private String name;
#OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Item> items;
}
#Entity
#Table(name = "item")
public class Item {
#Id private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "bid", referencedColumnName = "id")
private Bag bag;
}
and the repository:
#Repository
public interface BagRepository extends JpaRepository<Bag, Long> {
Bag findByUidAndName(Long uid, String name);
#Transactional
#Modifying
#Query(value = "DELETE FROM `bag` WHERE `uid` = :uid AND `name` = :name", nativeQuery = true)
void deleteByUidAndName(#Param("uid") Long uid, #Param("name") String name);
}
When I call bagRepository.deleteByUidAndName(uid, name), I get an Exception from hibernate relating to foreign key constraint. Setting spring.jpa.show-sql=true shows it does not try to delete the items first before deleting the bag.
However, if I call Bag bag = bagRepository.findByUidAndName(uid, name) and then bagRepository.deleteById(bag.getId()) everything is fine.
I'd like to know what's wrong about customizing this delete method and how to fix it.

In case deleting entity via bagRepository.deleteById(bag.getId()) Hibernate will remove from parent to child entity because you defined cascade = CascadeType.ALL on the relation. When we perform some action on the target entity, the same action will be applied to the associated entity.
Logic is in Hibernate and does not utilize database cascades.
#OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Item> items;
In case bagRepository.deleteByUidAndName(uid, name) you defined native query for deletion. This means that Hibernate logic will be ignored and the query will be executed as-is. You are working directly with the database in this case and to delete record via native SQL you need to define ON DELETE CASCADE on the database level to have similar logic.
#Query(value = "DELETE FROM `bag` WHERE `uid` = :uid AND `name` = :name", nativeQuery = true)
void deleteByUidAndName(#Param("uid") Long uid, #Param("name") String name);
Solution 1, #OnDelete(action = OnDeleteAction.CASCADE)
In case you have auto-generated tables you can add Hibernate-specific annotation #OnDelete to the relation. During tables generation ON DELETE CASCADE will be applied to the foreign key constraint.
Relation definition:
#OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
#OnDelete(action = OnDeleteAction.CASCADE)
private List<Item> items;
Auto generated constaint:
alter table item
add constraint FK19sn210fxmx43i8r3icevbeup
foreign key (bid)
references bag
on delete cascade
Implemetation:
import org.hibernate.annotations.OnDelete;
import org.hibernate.annotations.OnDeleteAction;
import javax.persistence.*;
import java.util.List;
#Entity
#Table(name = "bag")
public class Bag {
#Id
private Long id;
#Column(name = "uid")
private Long uid;
#Column(name = "name")
private String name;
#OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
#OnDelete(action = OnDeleteAction.CASCADE)
private List<Item> items;
}
Solution 2, #JoinColumn annotation with foreign key ON DELETE CASCADE
Specify foreign key with ON DELETE CASCADE for Item entity
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "bid", referencedColumnName = "id",
foreignKey = #ForeignKey(
name="FK_ITEMS_ID",
foreignKeyDefinition = "FOREIGN KEY (ID) REFERENCES ITEM(BID) ON DELETE CASCADE"))
private Bag bag;
Implementation:
import javax.persistence.*;
#Entity
#Table(name = "item")
public class Item {
#Id
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "bid", referencedColumnName = "id",
foreignKey = #ForeignKey(
name="FK_ITEMS_ID",
foreignKeyDefinition = "FOREIGN KEY (ID) REFERENCES ITEM(BID) ON DELETE CASCADE"))
private Bag bag;
}
Solution 3, do not use native query
In this case Hibernate logic will be applied.
Define repository like:
#Repository
public interface BagRepository extends JpaRepository<Bag, Long> {
Bag findByUidAndName(Long uid, String name);
#Transactional
#Modifying
void deleteByUidAndName(#Param("uid") Long uid, #Param("name") String name);
}
Solution 4, Add ON DELETE CASCADE manually to the database
In case your table is not auto-generated you can manually add ON DELETE CASCADE to the database.
alter table item
add constraint FK_BAG_BID
foreign key (bid)
references bag
on delete cascade

The DELETE statement conflicted with the REFERENCE constraint in dbo.interests

I am running into a problem deleting related entities from my database. I have a trading application where users can post trades and express their interests in other people's trades.
When a user deletes their account, all trades posted and interests expressed by this user should be removed from the database. However, the latter doesn't seem to work (I am also not sure if the first one works as I don't know in what order they get executed). I get the error:
The DELETE statement conflicted with the REFERENCE constraint "FKq9kr60l7n7h3yf82s44rkoe4g". The conflict occurred in database "dbi438161_i438161", table "dbo.interests", column 'user_id'.
Note: I get the same when I try to delete a trade but then the column is 'trade_id'
I do the same for the trades and roles of a user so I think it has to do with what is in my interest entity. I am using CascadeType.ALL annotation to let Hibernate remove related entities
Lists of related entities in user:
#ManyToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
#JoinTable(name="user_roles",
joinColumns = { #JoinColumn(name = "user_id") },
inverseJoinColumns = { #JoinColumn(name = "role_id") })
private List<Role> roles = new ArrayList<>();
#Transient
#JsonIgnore
#OneToMany(cascade=CascadeType.ALL, mappedBy="user")
private List<Interest> interests = new ArrayList<>();
#Transient
#JsonIgnore
#OneToMany(cascade=CascadeType.ALL, mappedBy="user")
private List<Trade> trades = new ArrayList<>();
Interest entity:
#Entity
#Table(name = "interests")
public class Interest {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int interestId;
#ManyToOne
#JoinColumn(name = "user_id", nullable = false)
private User user;
#ManyToOne
#JoinColumn(name = "trade_id", nullable = false)
private Trade trade;
private String comment;
public Interest(User user, Trade trade, String comment) {
this.user = user;
this.trade = trade;
this.comment = comment;
}
public Interest(){
}
}
For comparison, the trade entity:
#Entity
#Table(name = "trades")
public class Trade {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="trade_id")
private int tradeId;
#Column(name="wants")
private String wants;
#Column(name="offers")
private String offers;
#Column(name="date_last_modified")
private LocalDateTime lastModified;
#ManyToOne
#JoinColumn(name = "user_id", nullable = false)
private User user;
#Transient
#JsonIgnore
#OneToMany(cascade=CascadeType.ALL, mappedBy="trade")
private List<Interest> interests = new ArrayList<>();
public Trade(String wants, String offers, User user){
this.wants = wants;
this.offers = offers;
this.user = user;
}
public Trade() {
}
}
Does anybody have an idea on what I am doing wrong here? Thanks in advance

Try to set orphanRemoval to true for the following associations:
#OneToMany(cascade=CascadeType.ALL, mappedBy="user", orphanRemoval = true)
private List<Interest> interests = new ArrayList<>();
#OneToMany(cascade=CascadeType.ALL, mappedBy="user", orphanRemoval = true)
private List<Trade> trades = new ArrayList<>();
As it is stated in the documentation:
If the child entity lifecycle is bound to its owning parent so that the child cannot exist without its parent, then we can annotate the association with the orphanRemoval attribute and dissociating the child will trigger a delete statement on the actual child table row as well.
Please also note that you should not use cascade=CascadeType.ALL for the #ManyToMany association as it explained in the documentation:
For #ManyToMany associations, the REMOVE entity state transition doesn’t make sense to be cascaded because it will propagate beyond the link table. Since the other side might be referenced by other entities on the parent-side, the automatic removal might end up in a ConstraintViolationException.

How to do many-to-many relationship without deleting the previous data in mapping table using Hibernate or JPA

I have 2 Entities : User.java and PushNotification.java
and mapping table named as userpushnotification where many-to-many mapping takes place.
the existing data in userpushnotification table is a kind of important for me.
So if i try to add users(let's say id=5,6,7) for pushnotification(id=2), hibernate deletes the previous data for pushnotification(id=2) in relationship table and then it adds the new users for that pushnotification(id=2).
My need is to keep all the records in relationship table.
So how can i restrict the Hibernate/JPA to execute only insert queries intstead of executing delete and insert queries.
In simple words, I just want to append data in relationship table instead of overwriting.
User.java :-
#Entity
#Table(name = "user")
public class User implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name = "id")
#GenericGenerator(name = "gen", strategy = "identity")
#GeneratedValue(generator = "gen")
private long id;
#Column(name = "username")
private String username;
#Column(name = "password")
private String password;
#Column(name = "authkey")
private String authKey;
#ManyToMany(fetch = FetchType.EAGER, mappedBy = "users")
private Set<PushNotifications> pushNotifications = new HashSet<PushNotifications>();
PushNotifications.java :-
#Entity
#Table(name = "pushnotifications", uniqueConstraints = #UniqueConstraint(columnNames = { "id" }))
public class PushNotifications implements Serializable {
#Id
#Column(name = "id")
#GenericGenerator(name="gen",strategy="identity")
#GeneratedValue(generator="gen")
private long id;
#Column(name = "shortdescription")
private String shortDescription;
#Column(name = "title")
private String title;
#JsonIgnore
#ManyToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY)
#JoinTable(name = "userpushnotifications",
joinColumns = {#JoinColumn(name = "pushnotificatoinId") },
inverseJoinColumns = { #JoinColumn(name = "userId") })
private Set<User> users = new HashSet<User>();
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
When i try to do this :
PushNotifications notifications = iNotificationService
.getNotification(notificationId);
Set<User> newUsers = new HashSet<User>();
newUsers .add(newUserToBeNotified_1);
newUsers .add(newUserToBeNotified_2);
notifications.setUsers(newUsers);
sessionFactory.getCurrentSession().merge(notifications);
Here, am tring to add 2 users for that notification type, Already there is one user for that notification type in relationship table.
Hibernate executing these queries :
Hibernate:
delete
from
userpushnotifications
where
pushnotificatoinId=?
and userId=?
Hibernate:
insert
into
userpushnotifications
(pushnotificatoinId, userId)
values
(?, ?)
Hibernate:
insert
into
userpushnotifications
(pushnotificatoinId, userId)
values
(?, ?)
So, i hope u got me, i dont want hibernate to make delete operations.
Please help me resolve this, Looking for answers...
Thanks in advance.

You could use Blaze-Persistence for this which works on top of JPA and provides support for DML operations for collections. A query could look like the following
criteriaBuilderFactory.insertCollection(entityManager, PushNotifications.class, "users")
.fromIdentifiableValues(User.class, "u", newUsers)
.bind("id", notification.getId())
.bind("users").select("u")
.executeUpdate();
After setting Blaze-Persistence up like described in the documentation you can create a repository like this:
#Component
class MyRepository {
#Autowired CriteriaBuilderFactory cbf;
#Autowired EntityManager em;
public void addUsers(Collection<User> newUsers) {
cbf.insertCollection(em, PushNotifications.class, "users")
.fromIdentifiableValues(User.class, "u", newUsers)
.bind("id", notification.getId())
.bind("users").select("u")
.executeUpdate();
}
}
This will issue just the insert into the join table.

Java hibernate OneToOne: which side should be the owner

So i'm learning from these simple examples, there're 2 tables, USERS and USER_DETAILS, simple enough, each user has user_details and it's 1-to-1 relationship. So this sample is like this,
#Entity
#Table(name = "USERS")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "USR_ID")
private long id;
#Column(name = "USERNAME", nullable = false, unique = true)
private String username;
#Column(name = "PASSWORD")
private String password;
#OneToOne(cascade = CascadeType.ALL, mappedBy = "user", fetch = FetchType.LAZY)
private UserDetail userDetail;
//Setter and getter methods
}
#Entity
#Table(name = "USER_DETAILS")
public class UserDetail {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "USR_DET_ID")
private long id;
#Column(name = "FIRST_NAME")
private String firstName;
#Column(name = "LAST_NAME")
private String lastName;
#Column(name = "EMAIL")
private String email;
#Column(name = "DBO")
private LocalDate dob;
#OneToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "USR_ID")
private User user;
//Setter and Getter methods
}
If you look at mappedBy, it's in the User not UserDetails.
Q1: so USER is the owner, if it calls save(),
USER_DETAILS table will be updated as well ?
Q2: same examples put mappedBy in the USER_DETAILS side,
why people want to do this ?
How to determine which side to put mappedBy ?
Thanks for your help !

Q2: same examples put mappedBy in the USER_DETAILS side,
why people want to do this ?
How to determine which side to put mappedBy ?
In a bidirectional relationship, each entity has a relationship field
or property that refers to the other entity. Through the relationship
field or property, an entity class’s code can access its related
object. If an entity has a related field, the entity is said to “know”
about its related object.
There is a bidirectional one-to-one relationship in your example. Both User and UserDetail entities have a relationship field. #OneToOne annotation specified on both the entities.
For one-to-one bidirectional relationships, the owning side
corresponds to the side that contains the corresponding foreign key.
The owner of the relationship is UserDetail entity. The owner has #JoinColumn annotation to specify foreign key (USR_ID).
Inverse side of relationship (User) has mappedBy attribute.
Q1: so USER is the owner, if it calls save(),
USER_DETAILS table will be updated as well ?
In your example UserDetail is the owner. Therefore the saving process:
User user = new User(); // Ignoring the constructor parameters...
UserDetail userDetail = new UserDetail();
user.setUserDetail(userDetail);
userDetail.setUser(user);
userRepository.save(user);
You only need to save the parent. It will save the child as well.

Hibernate join columns not by a primary key reference

I have User and Role classes with ManyToMany relationship. When I'm adding Role object to List roles in User object the 'user_roles' table columns 'username' and 'role_name' gets populated with User and Role objects primary keys' which are their ids. I wanted to know whether its possible to reference not primary keys(ids) and get username and Role.name in those columns instead?
#Entity
#Table(name = "users")
#SecondaryTable(name = "user_info", pkJoinColumns = {
#PrimaryKeyJoinColumn(name = "info_id", referencedColumnName = "user_id") })
public class User {
#Id
#Column(name = "user_id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
#Column(name = "username")
private String username;
#Column(name = "password")
private String password;
#ManyToMany
#JoinTable(name="user_roles",
joinColumns= {#JoinColumn(name="username"/*, referencedColumnName="username"*/)},
inverseJoinColumns= {#JoinColumn( name="role_name"/*, referencedColumnName="role_name"*/)}
)
private List<Role> roles;
#Entity
#Table(name = "roles")
public class Role {
#Id
#Column(name = "role_id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
#Column(name = "role_name")
private String name;
#ManyToMany
private List<User> users;
Also if I remove the comments around referencedColumnName I get error when trying to fetch all users from the database. I haven't added any data to database so even when querying empty database I'm getting this error:
Caused by: org.hibernate.HibernateException: Found shared references
to a collection: com.recipee.model.User.roles
The reason I'm using such database schema is because I'm trying to use Tomcat realm authentication where I need username and role_name in one database table.