我有一个Group表,通过连接表与User表有ManyToMany关系。一个组可以包含很多用户,也可以包含包含更多用户的子组。
我正在使用JPA,Hibernate 3.3
注意:由于我已将此表达为ManyToMany关系,因此我没有实体表(对于连接表),也不确定如何在连接表上使用JPA执行任何查询。
@Entity
@Table(name = "group")
public class Group {
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false, insertable = false, updatable = false)
private Integer id;
@Column(name = "name", length = "255", nullable = false)
private String name;
@ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH}, fetch = FetchType.LAZY)
@JoinTable(name = "group_user", joinColumns = @JoinColumn(name = "group_id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
private List<User> users = new ArrayList<User>(0);
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinTable(name = "group_subgroup", joinColumns = @JoinColumn(name = "src_group_id"), inverseJoinColumns = @JoinColumn(name = "target_group_id"))
private List<Group> groups = new ArrayList<Group>(0);
答案 0 :(得分:1)
您可以在用户实体中添加private List<Group> groups
(懒惰)。并且,对于团体来说:
`SELECT u FROM User u JOIN u.groups g WHERE g=:group`
和子组:
`SELECT u FROM User u JOIN u.groups WHERE g IN (:groups)`
(并致电query.setParameter("groups", group.getGroups())
)