"XMLHttpRequest".equals(request.getHeader("X-Requested-With"));

这个是判断一个请求是传统的请求还是。ajax请求 

 第一种写法：

public ModelAndView resolveException(HttpServletRequest request,HttpServletResponse response, Object handler, Exception exception) {boolean isAjax = "XMLHttpRequest".equals(request.getHeader("X-Requested-With"));logger.error(getTrace(exception));        //如果是ajax请求         if (isAjax) { 

 第二种写法：参考CSDN shenzhenNBA 作者的

if (request.getHeader("x-requested-with") != null      && request.getHeader("x-requested-with").equalsIgnoreCase("XMLHttpRequest")) {      out.print("该请求是 AJAX 异步HTTP请求。");  }else{       out.print("该请求是传统的 同步HTTP请求。");