java JPA管理的不同实体映射错误

Question

我有一个表格，这个表格需要更新我的记录，但显然没有更新，我得到下面的错误消息。4天后处理这个异常，我决定问一个问题。如果你需要额外的信息，我可以补充一些

JSP异常

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异常

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

控制器；从表单中获取位置用户和域信息并保存到数据库

@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";
}

服务

@Service
@Transactional
public class UsersService {

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

形式

<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>

用户类

@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>();

“不同实体的托管映射”的含义是什么？我研究了这个错误消息，但我想没有人会得到这个错误Hibernate-orm

Answer 1

有时这只是冬眠中的一个错误：

https://hibernate.atlassian.net/browse/HHH-12439?attachmentViewMode=gallery

Description
Depending on the initialization order of entities a cascaded merge is failing with an IllegalStateException like:

08:26:15,502 ERROR [org.jboss.as.ejb3.invocation] (default task-1) WFLYEJB0034: 
EJB Invocation failed on component Bean for method public abstract void 
org.jboss.playground.BeanRemote.errorTest(java.lang.Long,java.lang.String):
javax.ejb.EJBException: java.lang.IllegalStateException:  
MergeContext#attempt to create managed -> managed mapping with different entities:    
[org.jboss.playground.Frd#9]; [org.jboss.playground.Frd#9]

...

Answer 2

此错误消息表示Hibernate检测到无效的“托管实体”->；'托管实体的映射，其中key！=价值观

MergeContext存储托管实体到合并实体的映射（反之亦然），我猜您可能同时加载了两个不同的托管实体，它们代表数据库中的同一条记录（这就是为什么会出现此错误）^{（来源：internal source code of Hibernate Core分析）}

从提供的示例中很难说另一个Users实体在哪里。所以我在这里写了一些想法：

• Users实体可以在Domains、Positions、UserLanguages、UserCertificates或UserKnowledge类中定义。如果在那里找到CascadeType.ALL/CascadeType.PERSIST，请删除cascade属性

• 如果在某个地方使用集合中的Users实体并试图将其持久化，则也可能会遇到此错误。重写Users类的equals()和hashCode()方法，并使用Set来确保对象的唯一性。equals()方法可能与比较ID一样简单：

  @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();
  }
  

• 仔细查找程序中的其他Users实体，并执行session.evict(users)从会话缓存中删除对象实例