JPA managed mapping with different entities error

Question

I have a form and this form need to update my record but apparently not updating and i get below error message. Dealing this exception with in 4 days and i decide to ask a question. If you need an extra information i can add some.

JSP Exception;

MergeContext#attempt to create managed -> managed mapping with different entities: [main.model.Users#1]; [main.model.Users#1]; nested exception is java.lang.IllegalStateException: MergeContext#attempt to create managed -> managed mapping with different entities: [main.model.Users#1]; [main.model.Users#1]

Java Exception;

java.lang.IllegalStateException: MergeContext#attempt to create managed -> managed mapping with different entities: [main.model.Users#1]; [main.model.Users#1]

Controller; its get Position User and Domain info from form and saves it to DB;

@PostMapping("/save-personel-info")
public String savePersonelInfo(@RequestParam int id, HttpServletRequest request, @ModelAttribute("Users") Users users, @ModelAttribute("Positions") Positions positions, @ModelAttribute("Domains") Domains domains, ModelMap model){
    usersService.save(users);
    request.setAttribute("mode", "MODE_USERS");
    return "redirect:/index";
}

Service;

@Service
@Transactional
public class UsersService {

    public void save(Users users){
        usersRepository.save(users);
    }
}

Form;

<form:form method="POST" action="/save-personel-info" modelAttribute="Users">
    <tr>
        <form:input id="1-1-0" type="hidden" class="form-control" path="id"/>
            <td><form:input id="1-1-0" type="text" class="form-control" path="username" /></td>
            <td><form:input id="1-1-0" type="text" class="form-control" path="mail" /></td>
        <td>
            <form:select path="Positions" class="form-control">
                <form:options items="${Pst}"  itemValue="id" itemLabel="position_name" />
            </form:select> 
        </td>                                   
        <td>
            <form:select path="Domains" class="form-control">
                <form:options items="${Domains}"  itemValue="id" itemLabel="domain_name" />
            </form:select> 
        </td>
    </tr>
    <input type="submit" value="Submit" />
</form:form>

User Class;

@Component
@Entity
public class Users {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long id;
    public String username;
    public String mail;

    @Temporal(TemporalType.DATE)
    public Date enrolment_date;

    @ManyToOne(cascade = CascadeType.ALL)
    public Domains domains;

    @ManyToOne(cascade = CascadeType.ALL)
    public Positions positions;

    @OneToMany(targetEntity = UserLanguages.class, mappedBy = "users", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public Set<UserLanguages> userlanguages = new HashSet<UserLanguages>();

    @OneToMany(targetEntity = UserCertificates.class, mappedBy = "users", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public Set<UserCertificates> usercertificates = new HashSet<UserCertificates>();

    @OneToMany(targetEntity = UserKnowledge.class, mappedBy = "users", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public Set<UserKnowledge> userknowledge = new HashSet<UserKnowledge>();

What is the meaning of "managed mapping with different entities" i research the this error message but i guess no one get this error. Hibernate-orm

Answer 1

This error message says that Hibernate has detected invalid 'managed entity' -> 'managed entity' mappings where key != value.

MergeContext stores mappings of managed entities to merged entities (and vice versa) and I guess that somehow you have two distinct managed entities loaded at the same time that represent the same record in the database (that's why you can get this error). ^{(Source: internal source code of Hibernate Core analysis)}

It's hard to say from the provided example where another one Users entity is. So I'm writing here a few ideas:

• Users entity may be defined in Domains, Positions, UserLanguages, UserCertificates, or UserKnowledge classes. If you find it there with CascadeType.ALL / CascadeType.PERSIST, remove cascade property.

• If somewhere you're using Users entities in a collection and trying to persist it, you may also encounter this error. Override equals() and hashCode() methods of Users class and use a Set to ensure object uniqueness. The equals() method may be as simple as comparing ids:

  @Override
  public boolean equals(Object o) {
      if (this == o) {
          return true;
      }
      if (o == null || getClass() != o.getClass()) {
          return false;
      }
  
      Users that = (Users) o;
  
      return getId() == that.getId();
  }
  
  @Override
  public int hashCode() {
      return Long.valueOf(getId()).hashCode();
  }
  

• Look carefully for other Users entities in your program and do session.evict(users) to remove the object instance from the session cache.