Hibernate 休眠级联删除孤立

我有两个实体：新闻和新闻评论

@Entity
@Table(name = "news", schema = "city")
public class News {

        private Set<CommentNews> comments = new HashSet<CommentNews>();
        ...
    @OneToMany(cascade={javax.persistence.CascadeType.ALL})
    @Cascade(CascadeType.DELETE_ORPHAN)
    @JoinColumn(name="news_id")
    public Set<CommentNews> getComments() {
        return comments;
    }
}

代码如下：

public void delete(int id) {
        T obj = null;
        session = HibernateUtil.openSession();
        try {
            session.beginTransaction();
            obj = (T) session.get(persistentClass, id);
            session.delete(obj);
            session.getTransaction().commit();
        } catch (HibernateException e) {
            session.getTransaction().rollback();
        } finally {
            session.close();
        }
    }

我明白了

Hibernate: update city.comment_news set news_id=null where news_id=?
    WARN : org.hibernate.util.JDBCExceptionReporter - SQL Error: 1048, SQLState: 23000
    ERROR: org.hibernate.util.JDBCExceptionReporter - Column 'news_id' cannot be null
    ERROR: org.hibernate.event.def.AbstractFlushingEventListener - Could not synchronize database state with session
    org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: 
Column 'news_id' cannot be null

---

我想同时删除新闻和评论新闻

此处的映射不正确：

在拥有端，您应该使用mappedBy来显示映射（JoinColumn）在另一端。你不应该两边都有一根柱子

您应该使用JPA注释，其中包括作为OneToMany的一部分的OrphanRemoving属性

@Entity
@Table(name = "news", schema = "city")
public class News {
    @OneToMany(mappedBy = "news", cascade={javax.persistence.CascadeType.ALL}, orphanRemoval = true)
    public Set<CommentNews> getComments() {
        return comments;
    }
}

---

希望这对你有用。

如果我没有一个自己的

@OneToMany

映射，我该怎么办。我只有

@ManyToOne

侧映射。

@Entity
@Table(name = "news", schema = "city")
public class News {
    @OneToMany(mappedBy = "news", cascade={javax.persistence.CascadeType.ALL}, orphanRemoval = true)
    public Set<CommentNews> getComments() {
        return comments;
    }
}

@Entity
@Table(name = "comment_news", schema = "city")
public class CommentNews {
    @ManyToOne
    @JoinColumn(name = "news_id")
    public News getNews() {
        return news;
    }
}