web.xml关于mime-mapping配置报错问题

[随风起飞]

<?xml version="1.0" encoding="UTF-8"?>
<!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标签报错 The content of element type "web-app" must match "(icon?,display-name?,description?,distributable?,context-param*,filter*,filter-mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env-ref*,resource-ref*,security-constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)" -->
<web-app>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>
			/WEB-INF/conf/applicationContext.xml,/WEB-INF/conf/biz.xml,/WEB-INF/conf/dao.xml
		</param-value>
	</context-param>
	<filter>
		<filter-name>struts2</filter-name>
		<filter-class>
			org.apache.struts2.dispatcher.FilterDispatcher
		</filter-class>
	</filter>
	<filter>
		<filter-name>swfFilter</filter-name>
		<filter-class>com.haolang.server.core.SwfFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>struts2</filter-name>
		<url-pattern>*.do</url-pattern>
	</filter-mapping>
	<filter-mapping>
		<filter-name>struts2</filter-name>
		<url-pattern>*.action</url-pattern>
	</filter-mapping>
	<filter-mapping>
		<filter-name>swfFilter</filter-name>
		<url-pattern>*.swf</url-pattern>
	</filter-mapping>
	<listener>
		<listener-class>
			org.springframework.web.context.ContextLoaderListener
		</listener-class>
	</listener>
	<servlet>
		<servlet-name>systemStartUp</servlet-name>
		<servlet-class>
			com.haolang.server.core.SystemInit
		</servlet-class>
		<load-on-startup>2</load-on-startup>
	</servlet>
        <!-- mime-mapping 报错 must match"(extension,mime-typ)" -->
	<mime-mapping>
		<extension>ppt</extension>
		<mime-type>application/vnd.ms-powerpoint</mime-type>
		<mime-type>
			application/vnd.openxmlformats-officedocument.presentationml.presentation
		</mime-type>
	</mime-mapping>
	<mime-mapping>
		<extension>pptx</extension>
		<mime-type>
			application/vnd.openxmlformats-officedocument.presentationml.presentation
		</mime-type>
	</mime-mapping>
	<session-config>
		<session-timeout>30</session-timeout>
	</session-config>
	<!-- Default page to serve -->
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
</web-app>

问题如上，本人对web.xml的配置一直不是很懂，这里面mime-mapping配置有错吗？
去掉mime-mapping 整个web-app还是报错。有没有人解说下！