public void doFilter(ServletRequest request, ServletResponse response,
      FilterChain chain) throws IOException, ServletException {
    HttpServletRequest servletRequest=(HttpServletRequest)request;
    HttpServletResponse servletResponse=(HttpServletResponse)response;
    // 判斷是否是 Ajax 請求，因為 Ajax 請求會追加 x-requested-with=XMLHttpRequest
    if("XMLHttpRequest".equalsIgnoreCase(servletRequest.getHeader("x-requested-with"))){
      servletResponse.addHeader("sessionstatus", "timeout");
    }    
    // 后續(xù)代碼省略......
  }

// 全局的ajax訪問，處理ajax清求時sesion超時
$.ajaxSetup({
  type: POST,
  contentType:"application/json;charset=utf-8",
  // 使用 complete 捕獲結(jié)果，做超時處理
  complete: function (XMLHttpRequest, textStatus) {
    var data = XMLHttpRequest.responseText;
    if (data == "timeout") {
      if( window.top != window.self ){
        window.top.location = "${pageContext.request.contextPath}";
      }
    }
  }
});