MyBatis映射器出错，已解决(Multiple annotations found at this line: - The content of element type "mapper" m)

创建UserMapper.xml文件时提示错误：Multiple annotations found at this line:
- The content of element type “mapper” must match “EMPTY”.
- Attribute “namespace” must be declared for element type
“mapper”.

这是因为配置文件约束错误，将文档类型从configuration改为mapper即可