如何删除现有记录并在Hibernate / JPA中的映射/子表上插入新记录

Question

Tables

+--------------+-------------+------------+
| USER         |             |            |
| ID           | USERNAME    |            |
| 1            | Jon         |            |
| 2            | Bob         |            |
| PROJECT      |             |            |
| ID           | PROJECTNAME |            |
| 1            | Java        |            |
| 2            | DevOps      |            |
| 3            | DotNet      |            |
| 4            | Testing     |            |
| 5            | Node        |            |
| USER_PROJECT |             |            |
| ID           | USER_ID     | PROJECT_ID |
| 1            | 1           | 1          |
| 2            | 1           | 2          |
| 3            | 1           | 3          |
+--------------+-------------+------------+

Classes

---

 User{
     ...
    @OneToMany(mappedBy="user", cascade=CascadeType.ALL, fetch=FetchType.LAZY, orphanRemoval=true)
        @Getter @Setter private Set<UserProject> userProjects;
    ...
    }

    Project{
        @OneToMany(mappedBy="project", cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval=true)
        @Fetch(FetchMode.JOIN)
        @Getter @Setter private Set<UserProject> userProjects;
    }

    UserProject{
        ....
        @ManyToOne
        @JoinColumn(name = "user_id")
        @Getter @Setter private User user;

        @ManyToOne
        @JoinColumn(name = "project_id")
        @Getter @Setter private Project project;

        @ManyToMany(cascade = {CascadeType.ALL}, fetch = FetchType.EAGER)
        @JoinTable(name="user_project_role",
            joinColumns={@JoinColumn(name="user_project_id")},
            inverseJoinColumns={@JoinColumn(name="role_id")})
        @Getter @Setter private Set<Role> roles;

    ...
    }

Service Implementation method:

public User updateUserDetails(User user){
        User updatedUser = userDAO.findOne(user.getId());
        for(Iterator<UserProject> iterator = updatedUser.getUserProjects().iterator(); iterator.hasNext();){
            UserProject userProject = iterator.next();
            if(!user.getUserProjects().contains(userProject)){
              //I have even changed the USER_PROJECT.USER_ID constraint to NOT-NULL for this line to work
              userProject.setUser(null);
            }
        }
        return userDAO.save(updatedUser);
    }

My UI provides options to ADD and also REMOVE existing projects for user.

I intend to delete and insert into USER_PROJECT. However I am unable to REMOVE existing projects for user. Iam only able to ADD newly selected projects for User.

What am I doing wrong here? Please comment if this is unclear.

Environment Hiberante 4.x/JPA, Spring 4.x/Spring Data JPA

Answer 1

I assume that the UserProject mapping is a consciuse choice because of the roles additional data (if not you normally do not map that table).

The orphan removal obviously cannot work as it is referenced by both User and Project table.

So to remove, you need to find the UserProject association, remove it from both sets on user and project, remove it explicit from the persistant contect, commit transaction.

For example something like that:

public User updateUserDetails(User template){
    User toUpdate = EM.find(User.class,template.getId());
    Set<UserProject> present = template.getUserProjects();//the ones should be kept
    Set<UserProject> toDel = new HashSet<>(toUpdate.getUserProjects());
    toDel.removeAll(present); //the difference so the once should be removed
    Set<UserProjcet> newOnes = new HashSet<>(present);
    newOnes.removeAll(toUpdate.getUserProjects()); //freshly added
    for (UserProject uP : toDel) {
        up.getProject().getUserProjects().remove(uP); //from each project removing reference to UserProject
        toUpdate.getUserProjects().remove(uP);
        EM.remove(uP); //removing the actuall 
    }
    toUpdate.getUserProjects().addAll(newOnes);
    return toUpdate;
}

It may also work (not sure yet) if you find the UserProjects to delete, set both user and project to null and remove it (you have to still call Em.remove on user project) without updating the lists.

Answer 2

First thing I didn't get where you are trying to delete the UserProject record in above code.

If updateUserDetails is the method where you are trying to delete the UserProject record, Then its wrong. Could you please clarify the things.