Web 开发中Ajax的Session 超时处理方法

  public void doFilter(ServletRequest request, ServletResponse response,
      FilterChain chain) throws IOException, ServletException {
    HttpServletRequest servletRequest=(HttpServletRequest)request;
    HttpServletResponse servletResponse=(HttpServletResponse)response;
    // 判断是否是 Ajax 请求，因为 Ajax 请求会追加 x-requested-with=XMLHttpRequest
    if("XMLHttpRequest".equalsIgnoreCase(servletRequest.getHeader("x-requested-with"))){
      servletResponse.addHeader("sessionstatus", "timeout");
    }    
    // 后续代码省略......
  }

// 全局的ajax访问，处理ajax清求时sesion超时
$.ajaxSetup({
  type: POST,
  contentType:"application/json;charset=utf-8",
  // 使用 complete 捕获结果，做超时处理
  complete: function (XMLHttpRequest, textStatus) {
    var data = XMLHttpRequest.responseText;
    if (data == "timeout") {
      if( window.top != window.self ){
        window.top.location = "${pageContext.request.contextPath}";
      }
    }
  }
});