报错信息：
Multiple annotations found at this line:
- Attribute "xmlns:xsi" must be declared for element type "web-app".
- The content of element type "web-app" must match "(icon?,display-name?,description?,distributable?,context-param*,filter*,filter-
mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env-ref*,resource-ref*,security-
constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)".
- Attribute "xsi:schemaLocation" must be declared for element type "web-app".
- Attribute "version" must be declared for element type "web-app".
- Attribute "xmlns" must be declared for element type "web-app".
