ManyToMany relationship, deleting records from relationship table

问题

Since 2h I'm trying to come up with the solution for the following problem, and I just can't find a proper way to do it:

I have three tables in MySQL db:

Role [role_id] [role_name]

Permission [permission_id] [permission_name]

PermissionToRole [permission_id] [role_id]

I have the Role class as the owner of the relationship:

@ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
@JoinTable(name="permissiontorole", 
            joinColumns={@JoinColumn(name="role_id")}, 
            inverseJoinColumns={@JoinColumn(name="permission_id")})

The Permission class mapping defined as:

@ManyToMany(mappedBy="permissions")
private Set<UserRole> userRoles = new HashSet<UserRole>();

Now, when I delete either permission or role those respective records are removed from their tables (this is expected and desired), but the relationship still remains in PermissionToRole table and I have no clue how to remove that whenever I delete either Role or Permission record. when i change the cascade type to ALL, then when i remove role or permission the relationship is removed but so is the other record e.g. if i remove role the permission is also removed.

Any ideas how to deal with it?

回答1:

You simply need to remove the permission from the Role.permissions collection, to remove the association between the role and the permission:

for (UserRole role: permissionToDelete.getUserRoles()) {
    role.getPermissions().remove(permissionToDelete);
}
em.remove(permissionToDelete);

来源：https://stackoverflow.com/questions/20728387/manytomany-relationship-deleting-records-from-relationship-table

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java

mysql

hibernate

jpa

Cascade