Mybatis获取参数值的各种情况

  /*
     * @author h
     * @desc
     * Mybatis中获取参数值的两种方式：${},#{}
     * ${}本质是字符串拼接
     * #{}本质是占位符
     * Mybatis获取参数值的各种情况：
     * 1、mapper接口方法的参数
     * 2、mapper接口方法的参数有多个
     *  此时Mybatis会将参数放入一个Map集合中，以两种方式进行存储
     * 3、若mapper接口方法的参数有多个时，可以手动将这些参数放在map中存储
     * 4、mapper接口方法的参数是实体类类型的参数
     *  通过属性来访问即可
     * 5、命名参数（注解）
     */
    @Test
    public void getAllUser(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        List<User> users = mapper.getAllUser();
        for (Object o: users
             ) {
            System.out.println(o);
        }
    }
    @Test
    public void getUserByUsername(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        User user = mapper.getUserByUsername("张三");
        System.out.println(user);
    }

    @Test
    public void checkLogin(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        User user = mapper.checkLogin("张三","123456");
        System.out.println(user);
    }

    @Test
    public void checkLoginByMap(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        Map<String,Object> map = new HashMap<>();
        map.put("username","张三");
        map.put("password","123456");
        User user = mapper.checkLoginByMap(map);
        System.out.println(user);
    }

    @Test
    public void insertUser(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        int result = mapper.insertUser(new User(null,"李四","abc123",23,"男","123@qq.com"));
        System.out.println(result);
    }

}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mybatis.mapper.ParameterMapper">
    <!--List<User> getAllUser();-->
    <select id="getAllUser" resultType="User">
        select * from t_user
    </select>

    <!--User getUserByUsername(String name)-->
    <select id="getUserByUsername" resultType="User">
                                                <!--#{}中的值可以为任意，只是想跟参数名保持一致-->
       <!-- select * from t_user where username = #{username}-->
        select * from t_user where username = ${username}
    </select>

    <!--User checkLogin(String username, String password);-->
    <select id="checkLogin" resultType="User">
        select * from t_user where username = #{arg0} and password = #{arg1}
    </select>

    <!--User checkLoginByMap(Map<String,Object> map);-->
    <select id="checkLoginByMap" resultType="User">
        select * from t_user where username = #{username} and password = #{password}
    </select>

    <!--int insertUser(User user);-->
    <insert id="insertUser">
        insert into t_user values(null, #{username},#{password},#{age},#{sex},#{email})
    </insert>
</mapper>