java 跨越访问 (jquery,jsonp)

前台页面代码:

  <script type="text/javascript">
    $(function(){
$.ajax({
type:"get",
async:false,
url:"http://localhost:8080/0hiCN/php-login/getAllNews?callback=?",
dataType:'jsonp',
processData: false,
success:function(data){
  alert(data.result); 
},
error:function(XMLHttpRequest, textStatus, errorThrown) {
  alert(XMLHttpRequest.status);
  alert(XMLHttpRequest.readyState);
  alert(textStatus); 
}});
});

    </script>

后台代码(SpringMVC):

        @RequestMapping(value="/getData",method = RequestMethod.GET)
  @ResponseBody
  public void getAllNews(HttpServletRequest request,HttpServletResponse response) throws IOException{
  try {  
         response.setContentType("text/plain");  
         response.setHeader("Pragma", "No-cache");  
         response.setHeader("Cache-Control", "no-cache");  
         response.setDateHeader("Expires", 0);  
         PrintWriter out = response.getWriter();  
         
         JSONObject json = new JSONObject();
         try {
json.put("result", true);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
         String jsonpCallback = request.getParameter("callback");//客户端请求参数  
         out.println(jsonpCallback+"("+json.toString()+")");//返回jsonp格式数据  
         out.flush();  
         out.close();  
       } catch (IOException e) {  
         e.printStackTrace();  
       }      
  }