Jquery ajax跨域访问的问题

$(document).ready(function(){ 


  var orderId="200902001"; 

  var userId="290001"; 

  

  var url ='http://dataservice.yimei.com/servlet/addChannelActivityDetail?orderId='+orderId+'&userId='+userId+'&callback=?'; 



  $.getJSON(url,function(data){}); 


 }); 


//注意 


1) 用$.getJSON这种方式; 


2) &callback=?这句很重要 


 //跨域 

String callback = request.getParameter("callback"); 

..... 

JSONArray jsonArray = JSONArray.fromObject(list); 

JSONObject json= new JSONObject(); 

json.put("users", jsonArray); 


response.getWriter().write(callback+"("+json.toString()+");");