用Struts2框架报错：The Struts dispatcher cannot be found

报错信息：The Struts dispatcher cannot be found.  This is usually caused by using Struts tags without the associated filter. Struts tags are only usable when the request has passed through its servlet filter, which initializes the Struts dispatcher needed for this tag.

报错原因：使用了struts2的标签库，但是没有正确的配置web.xml文件的过滤器

解决方法：

正确配置web.xml即可解决；

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
 3   <display-name>helloworld</display-name>
 4   <filter>
 5     <filter-name>struts2</filter-name>
 6     <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
 7   </filter>
 8   <filter-mapping>
 9     <filter-name>struts2</filter-name>
10     <url-pattern>/*</url-pattern>
11   </filter-mapping>
12   <welcome-file-list>
13     <welcome-file>index.html</welcome-file>
14     <welcome-file>index.htm</welcome-file>
15     <welcome-file>index.jsp</welcome-file>
16     <welcome-file>default.html</welcome-file>
17     <welcome-file>default.htm</welcome-file>
18     <welcome-file>default.jsp</welcome-file>
19   </welcome-file-list>
20 </web-app>

web.xml