Spring delete row of join table - mysql

Question

I have two entities User:
public class User {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Long userID;
#Column(name = "userHashedPassword")
private String password;
#Column(name = "userName")
private String userName;
#Column(name = "userEmail")
private String email;
#Transient
private List<String> groups = new LinkedList<>();
#ManyToMany
#JoinTable(name = "UserRoles",
joinColumns = #JoinColumn(
name = "userID"),
inverseJoinColumns = #JoinColumn(
name = "roleID"))
private Set<Role> roles = new HashSet<>();
#OneToMany(mappedBy = "user")
private Set<Rating> ratings;
protected User(){}
public User(String userHashedPassword, String userName, String email, Set<Role> roles){
this.password = userHashedPassword;
this.userName = userName;
this.email = email;
this.roles = roles;
}
//getters and setters
}
And Group:
#Table(name="FocusGroups")
#Entity
#JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,
property = "groupID")
public class Group {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long groupID;
private String groupName;
#ManyToMany
#JoinTable(name = "GroupMembers",
joinColumns = #JoinColumn(
name = "groupID"),
inverseJoinColumns = #JoinColumn(
name = "userID"))
private Set<User> groupMembers = new HashSet<>();
#ManyToOne(fetch = FetchType.EAGER, optional = true)
#JoinColumn(name="frameworkID", nullable = true)
private Framework framework;
public Group(){}
public Group(String groupName, Set<User> groupMembers, Framework framework) {
this.groupName = groupName;
this.groupMembers = groupMembers;
this.framework = framework;
}
//getters setters
}
When I delete a User, I want to remove them from group members, however it fails due to foreign key constraint: java.sql.SQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (capripol.groupmembers, CONSTRAINT FK98tbu0sjfsn1m5p340dn0v8wo FOREIGN KEY (userID) REFERENCES users (userID))
How do I work around this?

Answer 1

Well, I will try to answer: First of all, it is rather strange you refer on Groups in user
entity like that:
#Transient
private List<String> groups = new LinkedList<>();
It this case, you will not have a column group in user table in database, hence you have to first perform removal from group_members for an all groups:
delete from group_members where userid = <user_id_you_want_to_remove>;
And only after your JoinTable table does not contain any refers to user with <user_id_you_want_to_remove>, than you can execute
delete from users where userid = 1;
Note: there is no matter you do it by spring data (e.g. deleteById(Long id) and using #Query annotation specify the query above in SQL or HQL, up to you) - this will work. But I highly recommend you to reconsider you database structure - it is not cute to store only one entity.