ajax配合jsonp解决跨域访问问题

前端： 
$.ajax({ 
type:"get", 
async: false,//是否异步 
url:"http://ip:端口/servlet地址", 
dataType: "jsonp", 
contentType: "application/x-www-form-urlencoded;charset=UTF-8", 
jsonpCallback: "callback", 
data: { }, //传递的参数 
success: function(e){ 
  var r = $.parseJSON(e);//e：返回值 
}, 
error: function(XMLHttpRequest, textStatus, errorThrown) {} 
}); 
后台：用servlet做的样例 
String callback = request.getParameter("callback");//回调函数 
request.setCharacterEncoding("utf-8");//防止中文乱码 
response.setCharacterEncoding("utf-8");//防止中文乱码 
//response.setHeader("pragma", "no-cache"); 
//response.setHeader("cache-control", "no-cache"); 
//list要返回的结果 
JSONArray jsonArray = JSONArray.fromObject(list); 
response.getWriter().print(callback+"('"+jsonArray+"')");  
response.getWriter().flush();