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我正在使用 Json.NET 反序列化由 iOS 客户端（使用 Monotouch）上的 API 服务器发送的 json 文件。我有一个非常奇怪的问题，因为有时反序列化会因随机异常而失败。我之前没有任何问题，我认为它是从 json 文件变大开始的。发生这种情况时，我只是要求应用程序再试一次，并且在随机次数（并随机选择不同的异常）之后，反序列化最终会无缘无故地工作。

以下是我得到的不同例外：

  2013-02-12 19:14:58.307 client_ios[2176:4303] Failed to deserialize: Unexpected end of content while loading JObject.  
        at Newtonsoft.Json.Linq.JContainer.ReadTokenFrom (Newtonsoft.Json.JsonReader r) [0x00000] in <filename unknown>:0 
        at Newtonsoft.Json.Linq.JObject.Load (Newtonsoft.Json.JsonReader reader) [0x00000] in <filename unknown>:0 
        at shared.api.NotificationConverter.ReadJson (Newtonsoft.Json.JsonReader reader, System.Type objectType, System.Object existingValue, Newtonsoft.Json.JsonSerializer serializer) [0x00000] in /Users/xxx/Projects/xxx/shared/src/api/Notification.cs:23 
        at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueNonProperty (Newtonsoft.Json.JsonReader reader, System.Type objectType, Newtonsoft.Json.Serialization.JsonContract contract) [0x00000] in <filename unknown>:0 
        at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateList (IWrappedCollection wrappedList, Newtonsoft.Json.JsonReader reader, System.String reference, Newtonsoft.Json.Serialization.JsonArrayContract contract) [0x00000] in <filename unknown>:0 

Failed to deserialize: Unterminated string. Expected delimiter: ". Line 2530, position 69.  at Newtonsoft.Json.JsonTextReader.ReadStringIntoBuffer (Char quote) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.JsonTextReader.ParseString (Char quote) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.JsonTextReader.ParseValue (Char currentChar) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.JsonTextReader.ReadInternal () [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.JsonTextReader.Read () [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.Linq.JContainer.ReadContentFrom (Newtonsoft.Json.JsonReader r) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.Linq.JContainer.ReadTokenFrom (Newtonsoft.Json.JsonReader r) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.Linq.JObject.Load (Newtonsoft.Json.JsonReader reader) [0x00000] in <filename unknown>:0 
  at shared.api.NotificationConverter.ReadJson (Newtonsoft.Json.JsonReader reader, System.Type objectType, System.Object existingValue, Newtonsoft.Json.JsonSerializer serializer) [0x00000] in /Users/xxx/Projects/xxx/shared/src/api/Notification.cs:23 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueNonProperty (Newtonsoft.Json.JsonReader reader, System.Type objectType, Newtonsoft.Json.Serialization.JsonContract contract) [0x00000] in <filename unknown>:0 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateList (IWrappedCollection wrappedList, Newtonsoft.Json.JsonReader reader, System.String reference,     Newtonsoft.Json.Serialization.JsonArrayContract contract) [0x00000] in <filename unknown>:0

这是我用于反序列化的几行代码：

using (WebResponse webResponse = requestWeb.GetResponse()) {
    using (Stream responseStream = webResponse.GetResponseStream()) {
        using (StreamReader streamReader = new StreamReader(responseStream)) {
            using (JsonReader jsonReader = new JsonTextReader(streamReader)) {
                JsonSerializer serializer = new JsonSerializer();
                serializer.Converters.Add(creator);
                rsp = serializer.Deserialize<SimpleServerResponse>(jsonReader);
            }
        }
     }
}

它在 JObject.Load(reader) 处崩溃：

public class NotificationConverter : JsonConverter {

    public override bool CanConvert(Type objectType) {
        return typeof(ANotification).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) {
        JObject jobject = JObject.Load(reader);

        object target = null;

        JToken token = jobject["type_id"];

        if (token != null) {
            int id = token.ToObject<int>();

            switch (id) {
                case ANotification.STORY_INVITE:
                    target = new Notification<Moment>();
                    break;
                case ANotification.STORY_CONTENT_ADDED:
                    target = new Notification<Moment>();
                    break;
                case ANotification.STORY_LIKE:
                    target = new Notification<Moment>();
                    break;
                case ANotification.PICTURE_COMMENTED:
                    target = new Notification<PictureMomentPair>();
                    break;
                case ANotification.PICTURE_LIKED:
                    target = new Notification<PictureMomentPair>();
                    break;
                case ANotification.USER_FOLLOW:
                    target = new Notification<User>();
                    break;
                default:
                    break;
            }

            serializer.Populate(jobject.CreateReader(), target);
        }

        return target;
    }
}

关于我的 JsonConverter 的一些解释：服务器在 JSON 文件上发送的对象可能会根据“type_id”值而改变。JsonConverter 尝试读取 type_id 并根据它返回正确的对象。

我现在的解决方法是读取字符串中的整个流，然后将其传递给 json 反序列化器，但它在 iOS 上肯定更慢（更多 CPU 消耗）。

我不知道为什么有时它有效，有时无效。

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