webapp标签变成了
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSch...; xmlns="http://xmlns.jcp.org/xml/ns/j...; xmlns:web="http://xmlns.jcp.org/xml/ns/j...; xmlns:web="http://xmlns.jcp.org/xml/ns/j...; xsi:schemaLocation="http://java.sun.com/xml/ns/ja... http://java.sun.com/xml/ns/javaee/web-app_4_0.xsd http://xmlns.jcp.org/xml/ns/j... http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="4.0">
关键是我没动它,老自说自话加上那么一条
xmlns:web="http://xmlns.jcp.org/xml/ns/javaee"
之前的版本是
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSch...; xmlns="http://java.sun.com/xml/ns/ja...; xsi:schemaLocation="http://java.sun.com/xml/ns/ja... http://java.sun.com/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">