原网址：web.xml deployment descriptor examples 

  The web.xml is a configuration file to describe how a web application should be deployed. Here’re 5web.xml examples, just for self-reference.

  web.xml是一个配置文件来描述一个Web应用程序的部署。这里有5个web.xml的例子，仅供参考。

1. Servlet 3.1 deployment descriptor

Java EE 7 XML schema, namespace is http://xmlns.jcp.org/xml/ns/javaee/

<web-app 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" version="3.1"> </web-app>

2. Servlet 3.0 deployment descriptor

Java EE 6 XML schema, namespace is http://java.sun.com/xml/ns/javaee

<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"> </web-app>

3. Servlet 2.5 deployment descriptor

Java EE 5 XML schema, namespace is http://java.sun.com/xml/ns/javaee

<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"> </web-app>

4. Servlet 2.4 deployment descriptor

J2EE 1.4 XML schema, namespace is http://java.sun.com/xml/ns/j2ee

<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>

5. Servlet 2.3 deployment descriptor

J2EE 1.3 DTDs schema. This web.xml file is too old, highly recommend you to upgrade it.

<!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>