XML-MyBatis的Mapper配置文件

<?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="com.example.demo.mapper.UserMapper">

    <!-- 插入用户 -->
    <insert id="insertUser" parameterType="com.example.demo.entity.User">
        INSERT INTO user(name, email) VALUES(#{name}, #{email})
    </insert>

    <!-- 根据ID查询用户 -->
    <select id="findUserById" parameterType="int" resultType="com.example.demo.entity.User">
        SELECT * FROM user WHERE id = #{id}
    </select>

    <!-- 更新用户 -->
    <update id="updateUser" parameterType="com.example.demo.entity.User">
        UPDATE user SET name = #{name}, email = #{email} WHERE id = #{id}
    </update>

    <!-- 删除用户 -->
    <delete id="deleteUser" parameterType="int">
        DELETE FROM user WHERE id = #{id}
    </delete>

    <!-- 查询所有用户 -->
    <select id="findAllUsers" resultType="com.example.demo.entity.User">
        SELECT * FROM user
    </select>
</mapper>

这段XML内容是一个MyBatis的Mapper配置文件，用于定义数据库操作的SQL语句。以下是对每个部分的解释：

1. XML声明和DOCTYPE声明：

   <?xml version="1.0" encoding="UTF-8" ?>
   <!DOCTYPE mapper
     PUBLIC "-//myba