function getJson(){
    $.ajax({
        type:"get",
        dataType:"json",
        url:"<%=basePath %>getJson",
        success:function(data){
            for(var i=0;i<jsonData.length;i++){
                alert("Id："+data[i].id+"   username："+data[i].username);
            }
        },
 　　　　error:function(e){
　　　　　　alert(e);
　　    }
    })
}

    @ResponseBody
    @RequestMapping("/getJson")
    public Object getJson(){
        return new Object();
    }

    @RequestMapping("/getJson")
    public void getJson(HttpServletResponse response){
　　　　　Object obj = new Object();
　      JSONObject json = JSONObject.fromObject(obj);
        JsonUtils.ajaxJson(json.toString(), response);
    }

import java.io.IOException;

import javax.servlet.http.HttpServletResponse;

public class JsonUtils {
    public static void ajaxJson(String jsonString,HttpServletResponse response) {
        ajax(jsonString, "application/json",response);
    }
    public static void ajax(String content, String type,HttpServletResponse response) {
        try {
            response.setContentType(type + ";charset=UTF-8");
            response.setHeader("Pragma", "No-cache");
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expires", 0);
            response.getWriter().write(content);
            response.getWriter().flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}