MyBatis 入门开发 —-输入,输出参数

Posted 2020-11-05

第一: parameterType传入参数传递简单数据类型

<select id="findUserById" parameterType="int" resultType="cn.fy.domain.User">
    SELECT id,username,birthday,sex,address  FROM USER WHERE id = #{id}
    </select>

传递pojo对象

<!—传递pojo对象综合查询用户信息 -->
    user 使用了别名.
    <select id="findUserByUser" parameterType="user" resultType="user">
       select * from user where id=#{id} and username like ‘%${username}%‘
    </select>

    #{id} : 使用 user中的id
    ${username}:使用user中的username.
    // 如果参数类型user 中有属性 order 类
    <select id="findUserByUser" parameterType="user" resultType="user">
       select * from user where id=#{order.id} and username like ‘%${username}%‘
    </select>

mybatis可以通过ognl 表达式: #{属性.属性.属性}
传递hashmap

map综合查询用户信息 -->
    <select id="findUserByHashmap" parameterType="hashmap" resultType="user">
        select * from user where id=#{id} and username like ‘%${username}%‘
    </select>

     @Test
    public void findUserByHashmap() {
        SqlSession session = MyBatisUtil.getSession();

        UserMapper userMapper = session.getMapper(UserMapper.class);
        //构造查询条件Hashmap对象
        HashMap<String, Object> map = new HashMap<String, Object>();
        map.put("id", 1);
        map.put("username", "张");
        //传递Hashmap对象查询用户列表
        List<User>list = userMapper.findUserByHashmap(map);
        //关闭session
        session.close();
    }

    select * from user where id=? and username like ‘%管理员%‘

第二: resultType(输出类型)输出简单类型

select count(1) from user Public void testFindUserCount() throws Exception{ //获取session SqlSession session = sqlSessionFactory.openSession(); //获取mapper接口实例 UserMapper userMapper = session.getMapper(UserMapper.class); User user = new User(); user.setUsername("管理员"); //传递Hashmap对象查询用户列表 int count = userMapper.findUserCount(user); //关闭session session.close(); } 输出简单类型 select * from user where id = #{id} Public void testFindUserById() throws Exception { //获取session SqlSession session = sqlSessionFactory.openSession(); //获限mapper接口实例 UserMapper userMapper = session.getMapper(UserMapper.class); //通过mapper接口调用statement User user = userMapper.findUserById(1); System.out.println(user); //关闭session session.close(); } 输出pojo列表 select * from user where username like ‘%${value}%‘ @Test public void dimFind() { SqlSession session = MyBatisUtil.getSession(); List list = session.selectList("test1.findUserByUsername", "常山"); System.out.println(list); } 输出hashmap select username,sex from user @Test public void findUserNameAndSex() { SqlSession session = MyBatisUtil.getSession(); UserMapper userMapper = session.getMapper(UserMapper.class); //构造查询条件Hashmap对象 // 传递Hashmap对象查询用户列表 // 注意不能返回HashMap,还是要返回list List list = userMapper.findUserNameAndSex(); System.out.println("--list-" + list); //关闭session session.close(); } --list-[{sex=2, username=王五}, {sex=1, username=张三}, {sex=1, username=张小明}] resultMap resultMap 替代 resultType. ``` resultType可以指定pojo将查询结果映射为pojo，但需要pojo的属性名和sql查询的列名一致方可映射成功。 如果sql查询字段名和pojo的属性名不一致，可以通过resultMap将字段名和属性名作一个对应关系 ，resultMap实质上还需要将查询结果映射到pojo对象中。 resultMap可以实现将查询结果映射为复杂类型的pojo，比如在查询结果映射对象中包括pojo和list实现一对一查询和一对多查询。 ``` SELECT id,username,birthday,sex,address FROM USER WHERE id = #{id} -------------------------------- @Test public void findUserResultMap() throws Exception { SqlSession session = MyBatisUtil.getSession(); UserMapper userMapper = session.getMapper(UserMapper.class); //构造查询条件Hashmap对象 List list = userMapper.findUserResultMap(10); //--list-[User{id=10, username=‘张三‘, sex=‘1‘, birthday=Thu Jul 10 00:00:00 CST 2014, address=‘北京市‘}] System.out.println("--list-" + list); //关闭session session.close(); }