保存子数据时传递的分离实体可持久保存

  • Z时代
  • 2024-01-10
  • 分类：问答

提交表单时出现此错误：

org.hibernate.PersistentObjectException：分离的实体传递给持久化：com.project.pmet.model.Account; 嵌套异常是javax.persistence.PersistenceException：org.hibernate.PersistentObjectException：传递给持久对象的分离实体：com.project.pmet.model.Account

这是我的实体：

Account:

@Entity
@DynamicInsert
@DynamicUpdate
public class Account {
    @Id
    @GeneratedValue
    private Integer id;
    @Column(nullable = false)
    private String login;
    @Column(nullable = false)
    private String password;
    @Column(nullable = false)
    private String email;
    @ManyToOne
    @JoinColumn(name = "team_id")
    private Team team;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner")
    private List<Team> ownedTeams;
    ...

Team:

@Entity
@DynamicInsert
@DynamicUpdate
public class Team {
    @Id
    @GeneratedValue
    private Integer id;
    @Column(nullable = false)
    private String name;
    @ManyToOne
    @JoinColumn(name = "owner_id", nullable = false)
    private Account owner;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "team")
    private List<Account> members;
    ...

Here’s a part of the Controller:

    @ModelAttribute("team")
    public Team createTeamObject() {
        return new Team();
    }
    @RequestMapping(value = "/teams/create-team", method = RequestMethod.GET)
    public String getCreateTeam(@ModelAttribute("team") Team team, Principal principal) {
        logger.info("Welcome to the create team page!");
        Account owner = accountService.findOneByLogin(principal.getName());
        team.setOwner(owner);
        team.setMembers(new AutoPopulatingList<Account>(Account.class));
        return "teams";
    }
    @RequestMapping(value = "/teams/create-team", method = RequestMethod.POST)
    public String postCreateTeam(@ModelAttribute("team") Team team) {
        logger.info("Team created!");
        teamService.save(team);
        return "redirect:/teams.html";
    }

And the form:

<form:form commandName="team" id="teamForm">
      <div class="form-group">
          <label>Name</label>
          <form:input path="name" cssClass="form-control" />
      </div>
      <div class="form-group" id="row-template">
          <label>Members</label>
          <form:select path="members[0].id" cssClass="form-control" data-live-search="true" >
             <form:options items="${accounts}" itemValue="id" />
          </form:select>
          ...
      </div>
   <form:hidden path="owner.id" />
</form:form>

我究竟做错了什么？

回答：

teamService.save(team);

Save方法仅接受临时对象。你可以在这里找到什么是transient object 

Transient - an object is transient if it has just been instantiated using the new operator, and it is not associated with a Hibernate Session. It has no persistent representation in the database and no identifier value has been assigned. Transient instances will be destroyed by the garbage collector if the application does not hold a reference anymore. Use the Hibernate Session to make an object persistent (and let Hibernate take care of the SQL statements that need to be executed for this transition).

你正在获取Team对象，并尝试将其持久化到数据库中，但是该对象中包含Account对象，并且该Account对象已分离（意味着该对象的实例已保存到DB中，但该对象不在会话中）。Hibernate正在尝试保存它，因为你已指定：

@OneToMany(cascade = CascadeType.ALL, ....

因此，有几种方法可以解决它：

1）不要使用CascadeType.ALL配置。帐户对象可用于团队数（至少域结构允许），并且更新操作可能会更新所有团队的帐户-这意味着此操作不应在团队更新时启动。如果确实需要使用MERGE / DELETE配置，我将从那里删除级联参数（默认值是不执行级联操作）。但是，如果你确实需要坚持下去，请参阅选项＃2

2）使用“ saveOrUpdate（）”方法代替“ save（）”。“ saveOrUpdate（）”方法接受瞬态和分离的对象。但是这种方法的问题在于设计：在保存团队对象时，你真的需要插入/更新帐户吗？我将其分为两个操作，并阻止从团队更新帐户。

希望这可以帮助。

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