【Mybatis】学习笔记01：连接数据库，实现增删改

【Mybatis】学习笔记02：实现简单的查

【MyBatis】学习笔记03：配置文件进一步解读（非常重要）

【MyBatis】学习笔记04：配置文件模板

【MyBatis】学习笔记05：获取参数值的两种方式

【MyBatis】学习笔记06：各种查询所返回数据的数据类型

• 写法1：$
• 写法2：concat拼接
• 写法3：#（推荐使用）

写法1：$

    /**
     * 根据用户名模糊查询
     * @param username 用户名的关键字
     * @return  List<User> 用户列表
     */
    List<User> getUserByLike(@Param("username") String username);

<!--    List<User> getUserByLike(@Param("username") String username);-->
    <select id="getUserByLike" resultType="User">
         select * from t_users where userName like "%${username}%"
    </select>

    @Test
    public void testGetUserByLike(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
        List<User> list = mapper.getUserByLike("三");
        System.out.println(list);
    }

[User{userId='5',userName='张三'userCount='mllt@xrilang.com',userPassword='123'userGrade='0',userRegDate='null'userBlance='0'}, User{userId='6',userName='李三'userCount='xirlang@mllt.c',userPassword='124'userGrade='0',userRegDate='null'userBlance='0'}]

写法2：concat拼接

<!--    List<User> getUserByLike(@Param("username") String username);-->
    <select id="getUserByLike" resultType="User">
         <!-- select * from t_users where userName like "%${username}%"-->
        select * from t_users where userName like concat("%",#{username},"%")
    </select>
<!--concat 拼接-->

[User{userId='5',userName='张三'userCount='mllt@xrilang.com',userPassword='123'userGrade='0',userRegDate='null'userBlance='0'}, User{userId='6',userName='李三'userCount='xirlang@mllt.c',userPassword='124'userGrade='0',userRegDate='null'userBlance='0'}]

写法3：#（推荐使用）

<!--    List<User> getUserByLike(@Param("username") String username);-->
    <select id="getUserByLike" resultType="User">
         <!-- select * from t_users where userName like "%${username}%"-->
         <!-- select * from t_users where userName like concat("%",#{username},"%")-->
        select * from t_users where userName like "%"#{username}"%"
</select>

[User{userId='5',userName='张三'userCount='mllt@xrilang.com',userPassword='123'userGrade='0',userRegDate='null'userBlance='0'}, User{userId='6',userName='李三'userCount='xirlang@mllt.c',userPassword='124'userGrade='0',userRegDate='null'userBlance='0'}]