在xml文件里获取jvm环境变量

   <context-param>
             <param-name> contextConfigLocation</param-name >
             <param-value>
                  file:${home}${file.separator}amn_sms${file.separator} config${file.separator}context.xml
             </param-value>
   </context-param>
   <listener>
             <listener-class>
                  org.springframework.web.context.ContextLoaderListener
             </listener-class>
    </listener>