换成这样
<web-app id="calendar" version="3.0"
xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
metadata-complete="true"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee/ http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
“Latest Version: http://xmlns.jcp.org/xml/ns/javaee/”
refer to http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/javaee/index.html
<web-app id="calendar" version="3.0"
xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
metadata-complete="true"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee/ http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
“Latest Version: http://xmlns.jcp.org/xml/ns/javaee/”
refer to http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/javaee/index.html