我在解析给定的JSON数据时遇到了这个奇怪的问题。我有这样的JSON结构:
{"value":[
{"street":"Karlova 25"},
{"city":"Prague"},
{"gpsLat":"50.1571"},
{"gpsLon":"15.0482"}
]}
如何使用Newtonsoft JSON.NET库解析此结构?我尝试使用我自己的JsonConverter类:
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer){
JArray jarray = (JArray)((JTokenReader)reader).CurrentToken;
List<AddressValue> values = new List<AddressValue>();
foreach (var jobj in jarray.Children<JObject>()){
foreach (JProperty prop in jobj.Properties()){
values.Add(new AddressValue() { Label = prop.Name, Value = prop.Value.ToString() });
}
}
return values.ToArray();
}
class AddressValue{
public string Label { get; set; }
public string Value { get; set; }
}
但我有一个例外:
Exception thrown: 'Newtonsoft.Json.JsonSerializationException' in Newtonsoft.Json.DLL
Additional information: Unexpected token when deserializing object: StartObject. Path 'value[0]'.
编辑:我还试图将其保存到Dictionary:
[JsonProperty(PropertyName = "value")]
public Dictionary<string, string> Value{get; set;}
但我还有一个例外:
$exception {"Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'System.Collections.Generic.Dictionary`2[System.String,System.String]' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.rnTo fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.rnPath 'param.value'."}
我做错了什么?谢谢你的回答。
您不需要重新发明轮子。这种功能性已经发挥了作用。创建如下类:
public class Value
{
public string street { get; set; }
public string city { get; set; }
public string gpsLat { get; set; }
public string gpsLon { get; set; }
}
public class MyClass
{
public List<Value> value { get; set; }
}
现在,您可以简单地将json反序列化为poco对象。
MyClass result = JsonConvert.DeserializeObject<MyClass>(youJson);
您似乎希望将JSON中的Dictionary<string, string>
表示为对象数组,其中每个嵌套对象都有一个字典中的键和值。您可以使用以下转换器:
public class DictionaryToDictionaryListConverter<TKey, TValue> : JsonConverter
{
class DictionaryDTO : Dictionary<TKey, TValue>
{
public DictionaryDTO(KeyValuePair<TKey, TValue> pair) : base(1) { Add(pair.Key, pair.Value); }
}
public override bool CanConvert(Type objectType)
{
return typeof(IDictionary<TKey, TValue>).IsAssignableFrom(objectType) && objectType != typeof(DictionaryDTO);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var token = JToken.Load(reader);
var dict = (IDictionary<TKey, TValue>)(existingValue as IDictionary<TKey, TValue> ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator());
if (token.Type == JTokenType.Array)
{
foreach (var item in token)
using (var subReader = item.CreateReader())
serializer.Populate(subReader, dict);
}
else if (token.Type == JTokenType.Object)
{
using (var subReader = token.CreateReader())
serializer.Populate(subReader, dict);
}
return dict;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var dict = (IDictionary<TKey, TValue>)value;
// Prevent infinite recursion of converters by using DictionaryDTO
serializer.Serialize(writer, dict.Select(p => new DictionaryDTO(p)));
}
}
然后在您的容器类中使用它,如下所示:
public class RootObject
{
[JsonProperty("value")]
[JsonConverter(typeof(DictionaryToDictionaryListConverter<string, string>))]
public Dictionary<string, string> Value { get; set; }
}
请注意,如果密钥不是唯一的,转换器将在读取过程中引发异常。
更新
对于AddressValue
,您可以使用以下转换器:
public class AddressValueConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(AddressValue);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var addressValue = (existingValue as AddressValue ?? new AddressValue());
var token = JObject.Load(reader);
var property = token.Properties().SingleOrDefault();
if (property != null)
{
addressValue.Label = property.Name;
addressValue.Value = (string)property.Value;
}
return addressValue;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var addressValue = (AddressValue)value;
serializer.Serialize(writer, new Dictionary<string, string> { { addressValue.Label, addressValue.Value } });
}
}
然后按如下方式使用:
[JsonConverter(typeof(AddressValueConverter))]
public class AddressValue
{
public string Label { get; set; }
public string Value { get; set; }
}
public class RootObject
{
[JsonProperty("value")]
public List<AddressValue> Value { get; set; }
}
在这里演示两个选项。