json格式验证

 设置type=json

   "contactInfo": [
    {
      "type": "maxlength",
      "required": false,
      "isAdd": true,
      "isEdit": true,
      "max": 4000,
      "message": "【{contact_info}】值最大长度为4000。"
    },
    //json验证
    {
      "type": "json",
      "required": true,
      "isAdd": true,
      "isEdit": true,
      "message": "【{contact_info}】Json格式不正确。"
    }
    ]