Hibernate:由于违反外国钥匙的行为，不允许级联删除

Question

我正在研究一个Spring-MVC应用程序，在该应用程序中，我正在尝试删除与其他3个实体有一对一关系的实体。我已经标记了要在级联上删除的实体，但它不起作用。我遇到了违反外国密钥的错误。

注意实体：

@Entity
@Table(name="groupnotes")
public class GroupNotes {
    @OneToMany(mappedBy = "mnotedata",fetch = FetchType.EAGER,cascade = CascadeType.REMOVE)
    private Set<GroupAttachments> mattachments = new HashSet<>();
    public Set<GroupAttachments> getMattachments() {
        return this.mattachments;
    }
    public void setMattachments(Set<GroupAttachments> mattachments) {
        this.mattachments = mattachments;
    }
    @OneToMany(mappedBy = "mhistory",fetch = FetchType.LAZY,cascade = CascadeType.REMOVE)
    private Set<GroupNoteHistory> groupNoteHistorySet = new HashSet<>();
    public Set<GroupNoteHistory> getGroupNoteHistorySet(){
        return this.groupNoteHistorySet;
    }
    public void setGroupNoteHistorySet(Set<GroupNoteHistory> groupNoteHistorySet){
        this.groupNoteHistorySet = groupNoteHistorySet;
    }
    @OneToMany(mappedBy = "unreadNotes",fetch = FetchType.LAZY,cascade = CascadeType.REMOVE)
    private Set<UnreadNotes> unreadNotesSet = new HashSet<>();
    public Set<UnreadNotes> getUnreadNotesSet(){
        return this.unreadNotesSet;
    }
    public void setUnreadNotesSet(Set<UnreadNotes> unreadNotesSet){
        this.unreadNotesSet = unreadNotesSet;
    }
}

实体集群：

@Entity
@Table(name = "groupattachments")
public class GroupAttachments {
@ManyToOne
    @JoinColumn(name = "mnoteid")
    @OnDelete(action = org.hibernate.annotations.OnDeleteAction.CASCADE)
    private GroupNotes mnotedata;
    public void setMnotedata(GroupNotes mnotedata){this.mnotedata=mnotedata;}
    public GroupNotes getMnotedata(){return mnotedata;}
}

但是，当我执行以下代码时：

 @Override
    public boolean deleteAllNotesForSection(int msectionid) {
        session = this.sessionFactory.getCurrentSession();
        org.hibernate.Query query = session.createQuery("from GroupNotes as " +
                "n where n.ownednotes.msectionid=:msectionid");
        query.setParameter("msectionid",msectionid);
        List<GroupNotes> groupNotesList = query.list();
        for(GroupNotes groupNotes : groupNotesList){
            groupNotes.getGroupNoteHistorySet().clear();
            groupNotes.getMattachments().clear();
            groupNotes.getUnreadNotesSet().clear();
            session.flush();
        }
        org.hibernate.Query query1 = session.createQuery("delete from GroupNotes as " +
                "n where n.ownednotes.msectionid=:msectionid");
        query1.setParameter("msectionid",msectionid);
        query1.executeUpdate();
        session.flush();
        return true;
    }

执行上述代码时会出现以下错误：

SEVERE: Servlet.service() for servlet [appServlet] in context with path [] threw exception [Request processing failed; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
org.postgresql.util.PSQLException: ERROR: update or delete on table "groupnotes" violates foreign key constraint "groupnotes_groupnotehistory_fk" on table "groupnotehistory"
  Detail: Key (mnoteid)=(5455) is still referenced from table "groupnotehistory".

不是清除所有集合的第一个查询，应该从数据库中清除历史记录和所有内容。理想情况下，应该没有问题，因为它是级联删除。我还尝试使用query1.list和删除的前面删除来检索列表，但也无效。我不明白如何解决这个问题。非常感谢。

Answer 1

这里有几件事是错误的。首先，调用clear()仅处理双向关系的一侧。您需要访问每个孩子，并将其引用到 GroupNote到null。您写的方式，数据库将在冲洗后保持不变，不会删除任何实体。

第二，在HQL旁路中调用delete cascade选项。因此，即使没有第一个问题，也不会以这种方式删除相关实体，从而导致您看到的例外。