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) {

    vardata = XMLHttpRequest.responseText;

    if(data =="timeout") {

      if( window.top != window.self ){

        window.top.location ="${pageContext.request.contextPath}";

      }

    }

  }

});