要在Listener中获取HttpServletRequest，方法其实很简单：
ServletRequestAttributes rervletRequestAttributes = (ServletRequestAttributes)RequestContextHolder.currentRequestAttributes(); HttpServletRequest request = rervletRequestAttributes.getRequest();
但是有一种情况要特别注意， 就是请求不是来自于DispatcherServlet/DispatcherPortlet，例如filter之类。
这种情况下就必须得在web.xml里加入下面的listener：
<listener> <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class> </listener>
不然就会得到以下错误信息：
No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.