Hibernate 在尝试删除多对多关系中的实体时抛出异常答案

【问题标题】：Hibernate throws Exception while trying to delete Entity that in ManyToMany relationshipHibernate 在尝试删除多对多关系中的实体时抛出异常
【发布时间】：2015-02-24 23:52:55
【问题描述】：

Team 和 TeamMember 处于多对多关系。当我试图像这样删除团队时：

public void deleteTeam(int id) {
        Team team = (Team) getCurrentSession().get(Team.class, id);
        getCurrentSession().delete(team);
}

它给了：

org.springframework.dao.InvalidDataAccessApiUsageException: deleted object would be re-saved by cascade (remove deleted object from associations): [com.sprhib.model.Team#1]; 
    nested exception is org.hibernate.ObjectDeletedException: deleted object would be re-saved by cascade (remove deleted object from associations): [com.sprhib.model.Team#1]

然后我尝试从持有我需要删除的 TEAM 的团队成员实体中删除所有团队：

public void deleteTeam(int id) {
        Team team = getTeam(id);
        if(team != null){
            for(TeamMember tm: team.getTeamMembers()){
                for(Team t: tm.getTeams()){
                    if(t.getId() == team.getId()){
                        tm.getTeams().remove(t);
                    }
                }
            }
            getCurrentSession().delete(team);
        }
    }

但同样的错误仍然存在。首先，我希望 Hibernate 能够相应地管理多对多关系中的所有相关实体，因为它们具有注释。但它拒绝工作。什么鬼？

团队

@Entity
@Table(name="teams")
public class Team {


    private int id;

    private String name;

    private int rating;

    private Set<TeamMember> teamMembers;

    private Organization organization;

    @Id
    @NotNull
    @GeneratedValue(strategy = GenerationType.AUTO)
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @Length(max = 45)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @NotNull
    @Range(min = 0,max = 10)
    public int getRating() {
        return rating;
    }
    public void setRating(int rating) {
        this.rating = rating;
    }

    @NotNull
    @ManyToOne(fetch = FetchType.EAGER, cascade = {CascadeType.MERGE})
    @JoinColumn(name = "FK_Organization_id", nullable = false)
    public Organization getOrganization() {
        return organization;
    }

    public void setOrganization(Organization organization) {
        this.organization = organization;
    }

    @ManyToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(name = "team_member", joinColumns =
        @JoinColumn(name = "FK_Team_id", referencedColumnName= "id"),
            inverseJoinColumns = @JoinColumn(name = "FK_Member_id", referencedColumnName = "id")
    )
    public Set<TeamMember> getTeamMembers() {
        return teamMembers;
    }

    public void setTeamMembers(Set<TeamMember> teamMembers) {
        this.teamMembers = teamMembers;
    }
}

团队成员

@Entity
@Table(name="member")
public class TeamMember {

    private int id;

    private String name;

    private Set<Team> teams;

    @Id
    @NotNull
    @GeneratedValue(strategy = GenerationType.AUTO)
    public int getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }
    @NotEmpty
    @Length(max=100)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @NotNull
    @ManyToMany(fetch = FetchType.EAGER, mappedBy = "teamMembers", cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH, CascadeType.REMOVE}) // cascade!!!
    public Set<Team> getTeams(){
        return teams;
    }

    public void setTeams(Set<Team> teams) {
        this.teams = teams;
    }


}

【问题讨论】：

但是从团队中删除团队成员意味着什么？是否应该将 TeamMember 与 Team 解除关联，或者您是否真的要删除 TeamMember？也许 JPA/Hibernate 对这种歧义感到困惑

标签： java spring hibernate

【解决方案1】：

REMOVE 不应与 JPA 2.0 规范中的 @ManyToMany 一起使用。

关系建模注释限制了 cascade=REMOVE 规范的使用。 cascade=REMOVE 规范应仅应用于指定为 OneToOne 或 OneToMany 的关联。将 cascade=REMOVE 应用于其他关联的应用程序不可移植。

Hibernate 中有供应商扩展@OnDelete：

@OnDelete(action=OnDeleteAction.CASCADE)

【讨论】：