cvc-complex-type.2.3: Element 'web-app' cannot have character [children], because the type's content

Multiple annotations found at this line:
    - cvc-complex-type.2.3: Element 'web-app' cannot have character [children], because the type's content 
     type is element-only.

解:1

将头部文件

原来

<web-app version="3.0"
xmlns="http://Java.sun.com/xml/ns/javaee"

修改为

<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/j2ee"

解决2：不要粘贴，直接手写。或者将web.xml中有错误的部分删除重新写上，保存。