mapper.xml 的配置

Posted 2021-03-07 风中灵叶

<?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">

<!-- namespace：命名空间，用于隔离sql，还有一个很重要的作用，后面会讲 -->
<mapper namespace="test">
<!-- id:statement的id 或者叫做sql的id-->
<!-- parameterType:声明输入参数的类型 -->
<!-- resultType:声明输出结果的类型，应该填写pojo的全路径 -->
<!-- #{}：输入参数的占位符，相当于jdbc的？ -->

<!-- 通过id查询一个用户 -->
<select id="findUserById" parameterType="integer" resultType="com.itheima.domain.User">
select * from user where id=#{id};
</select>

<!-- 通过username 模糊查询用户列表
#{}: 占位符
${}：字符串拼接
-->
<select id="findUserByUsername" parameterType="String" resultType="com.itheima.domain.User">
select * from user where username like ‘%${value}%‘;
</select>


<!-- 添加用户 -->
<insert id="insertUser" parameterType="com.itheima.domain.User">
INSERT INTO user (username,birthday,sex,address) VALUES (#{username},#{birthday},#{sex},#{address});

</insert>

<!-- 更新用户 -->
<update id="updatetUser" parameterType="com.itheima.domain.User" >
update user set username=#{username} where id=#{id};
</update>

<!-- 删除用户 -->
<delete id="deleteUser" parameterType="integer">
delete from user where id= #{id};
</delete>

</mapper>