web.xml 各版本的 Schema 头部声明

"1.0" encoding="UTF-8"?>  
  
  
web-app>  
  display-name>Servlet 2.3 Web Applicationdisplay-name>  
web-app>

"1.0" encoding="UTF-8"?>  
web-app version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee  
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">  

web-app>

"1.0" encoding="UTF-8"?>  
web-app version="2.5" 
    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_2_5.xsd">  

web-app>

"1.0" encoding="UTF-8"?>
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>

"1.0" encoding="UTF-8"?>
web-app version="3.1" 
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
    http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">

web-app>

"1.0" encoding="UTF-8"?>

web-app version="4.0" 
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee　　　    　 　　
    http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd">
  
web-app>
转自：https://www.cnblogs.com/wumz/p/10716512.html