HttpServletRequest httpRequest=(HttpServletRequest)request;  

 String strBackUrl = "http://" + request.getServerName() //服务器地址

                     + ":"

                     + request.getServerPort()           //端口号

                     + httpRequest.getContextPath()      //项目名称

                     + httpRequest.getServletPath()      //请求页面或其他地址

                 + "?" + (httpRequest.getQueryString()); //参数