Multiple annotations found at this line: - The content of element type "mapper" must match "EMPTY". - Attribute "namespace" must be declared for element type "mapper".

今天在mybatis的mapper映射配置文件中遇到了这样的问题，困扰了我3个小时：

Multiple annotations found at this line:
- The content of element type "mapper" must match "EMPTY".
- Attribute "namespace" must be declared for element type
"mapper".

代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<mapper namespace="com.ckx.entity.User">
</mapper>

第四行mapper标签一直报错！找不到问题原因，也百度尝试了百家学说，终无成就。无奈改了下表头格式如下：

<?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.ckx.entity.User">
</mapper>

毛主席万岁！问题解决了！可为什么有什么不一样吗？

这个放原因在于头部的医用错误  ：   

http://mybatis.org/dtd/mybatis-3-mapper.dtd