**UserMapper.java** ~~~ //根据多个id查询，in的用法 List<User> findByIdList(@Param("ids") List<Integer> ids); ~~~ **UserMapper.xml** ~~~ <select id="findByIdList" resultMap="userMapper"> select * from t_user <where> <!-- collection:指定要遍历的(数据|集合)对象 item: 为当前遍历的元素指定一个引用 open: 条件左半部分 close: 条件右半部分 separator:每个元素的分割符 --> <foreach collection="ids" item="id" open="u_id in (" separator="," close=")"> #{id} </foreach> </where> </select> ~~~ **测试代码** ~~~ @Test public void testFindByIds(){ List<Integer> ids = new ArrayList<>(); ids.add(15); ids.add(16); ids.add(17); UserMapper mapper = session.getMapper(UserMapper.class); System.out.println(mapper.findByIdList(ids)); } ~~~