我解决了类似的问题并找到了一个解决方案。这个方法不是很优雅,我认为应该有更好的方法,但至少它能够工作。所以我的想法是针对每个实现了
IBar
接口的类型都有一个
JsonConverter
,并且还有一个针对
IBar
本身的转换器。
让我们从模型开始:
public interface IBar { }
public class BarA : IBar { }
public class Foo
{
public IBar Bar { get; set; }
}
现在让我们为
IBar
创建转换器。它仅在反序列化JSON时使用。它将尝试读取
$type
变量并调用实现类型的转换器:
public class BarConverter : JsonConverter
{
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotSupportedException();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var jObj = JObject.Load(reader);
var type = jObj.Value<string>("$type");
if (type == GetTypeString<BarA>())
{
return new BarAJsonConverter().ReadJson(reader, objectType, jObj, serializer);
}
throw new NotSupportedException();
}
public override bool CanConvert(Type objectType)
{
return objectType == typeof (IBar);
}
public override bool CanWrite
{
get { return false; }
}
private string GetTypeString<T>()
{
var typeOfT = typeof (T);
return string.Format("{0}, {1}", typeOfT.FullName, typeOfT.Assembly.GetName().Name);
}
}
这是BarA
类的转换器:
public class BarAJsonConverter : BarBaseJsonConverter
{
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
GetSerializer().Serialize(writer, value);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var existingJObj = existingValue as JObject;
if (existingJObj != null)
{
return existingJObj.ToObject<BarA>(GetSerializer());
}
throw new NotImplementedException();
}
public override bool CanConvert(Type objectType)
{
return objectType == typeof(BarA);
}
}
您可能会注意到它继承自
BarBaseJsonConverter
类,而不是
JsonConverter
。另外,我们在
WriteJson
和
ReadJson
方法中不使用
serializer
参数。在自定义转换器中使用
serializer
参数存在问题。您可以在
这里了解更多信息。我们需要创建
JsonSerializer
的新实例,而基类是一个很好的选择:
public abstract class BarBaseJsonConverter : JsonConverter
{
public JsonSerializer GetSerializer()
{
var serializerSettings = JsonHelper.DefaultSerializerSettings;
serializerSettings.TypeNameHandling = TypeNameHandling.Objects;
var converters = serializerSettings.Converters != null
? serializerSettings.Converters.ToList()
: new List<JsonConverter>();
var thisConverter = converters.FirstOrDefault(x => x.GetType() == GetType());
if (thisConverter != null)
{
converters.Remove(thisConverter);
}
serializerSettings.Converters = converters;
return JsonSerializer.Create(serializerSettings);
}
}
JsonHelper
是一个用于创建JsonSerializerSettings
的类:
public static class JsonHelper
{
public static JsonSerializerSettings DefaultSerializerSettings
{
get
{
return new JsonSerializerSettings
{
Converters = new JsonConverter[] { new BarConverter(), new BarAJsonConverter() }
};
}
}
}
现在它将正常工作,并且您仍然可以使用自定义转换器进行序列化和反序列化:
var obj = new Foo { Bar = new BarA() }
var json = JsonConvert.SerializeObject(obj, JsonHelper.DefaultSerializerSettings)
var dObj = JsonConvert.DeserializeObject<Foo>(json, JsonHelper.DefaultSerializerSettings)