Mybatis中配置xml时报Wrong root element: 5Attribute namespace is not allowed here: 5错误解决方法（idea）

初学者容易犯的错误

在MyBatis官网中复制

<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

后忘记修改

原

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<mapper namespace="userMapper">
    <select id="findAll" resultType="com.itrs.domain.User">
        select * from user
    </select>
</mapper>

改

<?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="userMapper">
    <select id="findAll" resultType="com.itrs.domain.User">
        select * from user
    </select>
</mapper>