web.xml 各版本

Servlet 2.3

<!DOCTYPE web-app PUBLIC  
    "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"  
    "http://java.sun.com/dtd/web-app_2_3.dtd" >  

<web-app>  
    <display-name>Servlet 2.3 Web Application</display-name>  
</web-app>  

Servlet 2.4

<web-app 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"  
    version="2.4">  
    <display-name>Servlet 2.4 Web Application</display-name>  
</web-app> 

Servlet 2.5

<web-app 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"  
    version="2.5">  
    <display-name>Servlet 2.5 Web Application</display-name>  
</web-app>  

Servlet 3.0

<?xml version="1.0" encoding="UTF-8"?> 
<web-app 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"  
          version="3.0">  
  <display-name>Servlet 3.0 Web Application</display-name>  
</web-app>