我正在尝试以级联方式映射两个多对多关联。我有三个类:用户、用户组和权限。第一个与第二个具有多对多关联,而第二个与第三个具有多对多关联。
我正在使用休眠 4.2.0
@Entity
@Table(name = "user")
public class User implements Serializable {
@ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, targetEntity = org.weedea.bidupsys.user.logic.model.UserGroup.class)
@JoinTable(name = "UserGroupUser", joinColumns = { @JoinColumn(name = "userId") }, inverseJoinColumns = { @JoinColumn(name = "userGroupId") })
private List<UserGroup> userGroupList = null;
}
@Entity
@Table(name = "userGroup")
public class UserGroup implements Serializable {
@ManyToMany(fetch = FetchType.EAGER, targetEntity = org.weedea.bidupsys.user.logic.model.Permission.class, cascade = { CascadeType.ALL })
@JoinTable(name = "UserGroupPermission", joinColumns = { @JoinColumn(name = "userGroupId") }, inverseJoinColumns = { @JoinColumn(name = "permissionId") })
private List<Permission> permissionList = null;
}
使用这个配置我得到一个错误,因为我尝试同时加载两个急切的集合:
javax.servlet.ServletException: cannot simultaneously fetch multiple bags
javax.faces.webapp.FacesServlet.service(FacesServlet.java:229)
如果我将 fetch = FetchType.LAZY 放在第二个集合上,我会收到另一个错误:
failed to lazily initialize a collection of role: org.weedea.bidupsys.user.logic.model.UserGroup.permissionList, could not initialize proxy - no Session
我怎么能映射这两个多对多关联?感谢帮助!