web.xml 3.0头文件

<web-app  

        version="3.0"  

        xmlns="http://java.sun.com/xml/ns/javaee"  

        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  

        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

</web-app  >