以下這種寫法對於我來說不行，但我們老師就是這樣寫的

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper SYSTEM "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd" PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN">
<mapper namespace="..."> 
</mapper>

下面是我在網上看到的，實驗後可行

<?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">