sitemesh装饰页面
步骤：
1，引入sitemesh的jar包
2，引入struts2对sitemesh的支持包：struts2-sitemesh-plugin-x.x.x.jar
3，修改web.xml文件，添加ActionContextCleanup和sitemesh过滤器
<filter><filter-name>struts-cleanup</filter-name><filter-class>org.apache.struts2.dispatcher.ActionContextCleanUp</filter-class></filter><filter><filter-name>sitemesh</filter-name><filter-class>org.apache.struts2.sitemesh.FreeMarkerPageFilter</filter-class></filter><filter-mapping><filter-name>struts-cleanup</filter-name><url-pattern>/*</url-pattern></filter-mapping><filter-mapping><filter-name>sitemesh</filter-name><url-pattern>/*</url-pattern></filter-mapping>
4，提供decorators.xml配置文件，在这个配置文件中定义装饰器的路径，需要放到WEB-INF目录下
5，创建装饰器
6，使用装饰器
????? -->在头部添加一条语句：<meta name="decorator" content="navigation">
