**1.UserMapper.java** ~~~ //根据id查询用户User关联的Role User findById2(int id); ~~~ **2.UserMapper.xml** ~~~ <resultMap id="userMapperWithRole1" type="User"> <id property="id" column="u_id"></id> <result property="name" column="u_name"></result> <result property="password" column="u_password"></result> <collection property="roles" ofType="Role" select="findRolesByUserId" column="u_id" fetchType="lazy"> </collection> </resultMap> <select id="findById2" resultMap="userMapperWithRole1"> select * from t_user where u_id = #{id} </select> ~~~ **3.UserMapper.java** ~~~ //根据用户id查询关联的角色对象 List<Role> findRolesByUserId(int uid); ~~~ **4.UserMapper.xml** ~~~ <select id="findRolesByUserId" resultType="Role" > SELECT r.* FROM user_role ur,role r WHERE ur.rid = r.id AND ur.uid = #{uid} </select> ~~~ **5.测试代码** ~~~ @Test public void testFindById2(){ UserMapper mapper = session.getMapper(UserMapper.class); System.out.println(mapper. findById2(15)); } ~~~