两表通过中间表多对多关联用HQL查询
如有user表，role表，userrole表，3者之间的关系是，user表和role表通过userrole表多对多关联。 定义user类：[code="java"]public class user implements java.io.Serializable {private Integer userId;private String userName;private Set userrole= new HashSet(0);//get和set省略}[/code] 定义role类：[code="java"]public role implements java.io.Serializable {private Integer roleId;private String roleName;private Set userrole= new HashSet(0);//get和set省略}[/code] 定义userrole类：[code="java"]public userrole implements java.io.Serializable {private Integer userroleID;private role role;private user user;//get和set省略}[/code]对应的xml：[code="java"]<!--只捡关联部分--><!--user--> <key><column name="userId" not-null="true"></column></key><one-to-many not-null="true"></column></key><one-to-many fetch="select"><column name="roleId" not-null="true"></column></many-to-one><many-to-one name="user" fetch="select"><column name="userId" not-null="true"></column></many-to-one>[/code]问题是：如何用hql查找出角色为admin的用户的id和名字？hql：[code="java"]select u.userId,u.userName from user u,userrole ur,role r where u.userID in(ur.user) and r.roleName='admin' and ur.userroleID in elements(r.userrole)[/code]本例用到了in和in elements关键字，区别在于in elements用于set，in用于实例对象。