关于jquery dataTables 插件的使用！

后台返回的如下格式的数据：
{
    "sEcho": 3,
    "iTotalRecords": 57,
    "iTotalDisplayRecords": 57,
    "aaData": [
        {
            "DT_RowId": "row_7",
            "DT_RowClass": "gradeA",
            "0": "Gecko",
            "1": "Firefox 1.0",
            "2": "Win 98+ / OSX.2+",
            "3": "1.7",
            "4": "A"
        },
        {
            "DT_RowId": "row_8",
            "DT_RowClass": "gradeA",
            "0": "Gecko",
            "1": "Firefox 1.5",
            "2": "Win 98+ / OSX.2+",
            "3": "1.8",
            "4": "A"
        }
        
    ]
}怎么不能放到 前台的table里面 ，这是什么原因呢？？
我按照文档上的 方法
  $('#example').dataTable( {
  "bProcessing": true,
  "bServerSide": true,
  "sAjaxSource": "../jsonServlet",
  "contentType":"application/json",
  "sEcho": 3,
  
          "fnServerData": function ( sSource, aoData, fnCallback ) {
$.ajax( {
"dataType": 'json', 
"type": "POST", 
 "url": sSource, 
                                 "data": aoData, 
"success": fnCallback
} );求指点