ajax提交session超时跳转页面使用全局的方法来处理

public void doFilter(ServletRequest request, ServletResponse response, 
FilterChain chain) throws IOException, ServletException { 
HttpServletRequest httprequest = (HttpServletRequest) request; 
HttpServletResponse httpresponse = (HttpServletResponse) response; 
String url = httprequest.getRequestURL().toString(); 
if (httprequest.getSession()== null) { 
if (httprequest.getHeader("x-requested-with") != null 
&& httprequest.getHeader("x-requested-with").equals( 
"XMLHttpRequest")) { // ajax请求 
httpresponse.setHeader("sessionstatus", "timeout"); 
} else { 
httpresponse.sendRedirect("/test/index.jsp"); 
return; 
} 
} else { 
chain.doFilter(request, response); 
} 
}

//全局的ajax访问，处理ajax清求时sesion超时 
$.ajaxSetup({ 
contentType : "application/x-www-form-urlencoded;charset=utf-8", 
complete : function(XMLHttpRequest, textStatus) { 
var sessionstatus = XMLHttpRequest.getResponseHeader("sessionstatus"); // 通过XMLHttpRequest取得响应头，sessionstatus， 
if (sessionstatus == "timeout") { 
// 如果超时就处理 ，指定要跳转的页面 
window.location.replace("/test/index.jsp"); 
} 
} 
});