判断是否ajax请求

/**
 * 判断ajax请求
 * @param request
 * @return
 */
boolean isAjax(HttpServletRequest request){
    return  (request.getHeader( "X-Requested-With" ) != null  && "XMLHttpRequest" .equals( request.getHeader( "X-Requested-With" ).toString())   ) ;
}

ajax返回值有<pre>标签时，ajax添加属性dataType为text类型即可！