使用JSON.NET将异构JSON数组反序列化为协变List <>

我有一个JSON数组包含具有不同属性的不同types的对象。 其中一个属性称为“types”，并确定数组项目的types。 这里是我的数据的一个例子：

[{ type : "comment", text : "xxxx" }, { type : "code", tokens : [{ type : "ref", data : "m" }, { type : "operator", data : "e" } ] }, { type : "for", boundLocal : { type : "local", name : "i", kind : "Number" }, upperBound : { type : "ref", tokens : [{ type : "operator", data : "3" }, { type : "operator", data : "0" } ] }, body : [{ type : "code", tokens : [{ type : "ref", data : "x" } ] }, { type : "code", tokens : [{ type : "ref", data : "y" } } ] ] ] 

为了将这些对象映射到我的.Net实现，我定义了一组类：一个基类和几个子类（具有复杂的层次结构，具有4个“代”）。 这只是这些类的一个小例子：

 public abstract class TExpression { [JsonProperty("type")] public string Type { get; set; } } public class TComment : TExpression { [JsonProperty("text")] public string Text { get; set; } } public class TTokenSequence : TExpression { [JsonProperty("tokens")] public List<TToken> Tokens { get; set; } } 

我想要达到的是能够将这个数组反序列化到一个协变generics列表中，声明如下：

 List<TExpression> myexpressions = JsonConvert.DeserializeObject<List<TExpression>>(aststring); 

这个列表应该包含从TExpressioninheritance的适当的子类的实例，所以我可以在以后的代码中使用下面的代码：

 foreach(TExpression t in myexpressions) { if (t is TComment) dosomething; if (t is TTokenSequence) dosomethingelse; } 

我怎样才能达到使用JSON.NET？

Answer 1

这里是一个使用CustomCreationConverter的例子。

 public class JsonItemConverter : Newtonsoft.Json.Converters.CustomCreationConverter<Item> { public override Item Create(Type objectType) { throw new NotImplementedException(); } public Item Create(Type objectType, JObject jObject) { var type = (string)jObject.Property("valueType"); switch (type) { case "int": return new IntItem(); case "string": return new StringItem(); } throw new ApplicationException(String.Format("The given vehicle type {0} is not supported!", type)); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { // Load JObject from stream JObject jObject = JObject.Load(reader); // Create target object based on JObject var target = Create(objectType, jObject); // Populate the object properties serializer.Populate(jObject.CreateReader(), target); return target; } } public abstract class Item { public string ValueType { get; set; } [JsonProperty("valueTypeId")] public int ValueTypeId { get; set; } [JsonProperty("name")] public string Name { get; set; } public new virtual string ToString() { return "Base object, we dont' want base created ValueType=" + this.ValueType + "; " + "name: " + Name; } } public class StringItem : Item { [JsonProperty("value")] public string Value { get; set; } [JsonProperty("numberChars")] public int NumberCharacters { get; set; } public override string ToString() { return "StringItem object ValueType=" + this.ValueType + ", Value=" + this.Value + "; " + "Num Chars= " + NumberCharacters; } } public class IntItem : Item { [JsonProperty("value")] public int Value { get; set; } public override string ToString() { return "IntItem object ValueType=" + this.ValueType + ", Value=" + this.Value; } } class Program { static void Main(string[] args) { // json string var json = "[{\"value\":5,\"valueType\":\"int\",\"valueTypeId\":1,\"name\":\"numberOfDups\"},{\"value\":\"some thing\",\"valueType\":\"string\",\"valueTypeId\":1,\"name\":\"a\",\"numberChars\":11},{\"value\":2,\"valueType\":\"int\",\"valueTypeId\":2,\"name\":\"b\"}]"; // The above is deserialized into a list of Items, instead of a hetrogenous list of // IntItem and StringItem var result = JsonConvert.DeserializeObject<List<Item>>(json, new JsonItemConverter()); foreach (var r in result) { // r is an instance of Item not StringItem or IntItem Console.WriteLine("got " + r.ToString()); } } } 

Answer 2

CustomCreationConverter应该能够处理这个。

Answer 3

它也可以用声明的方式用JsonSubTypes实现：

 [JsonConverter(typeof(JsonSubtypes), "valueType")] [JsonSubtypes.KnownSubType(typeof(IntItem), "int")] [JsonSubtypes.KnownSubType(typeof(StringItem), "string")] public abstract class Item { public string ValueType { get; set; } [JsonProperty("valueTypeId")] public int ValueTypeId { get; set; } [JsonProperty("name")] public string Name { get; set; } public override string ToString() { return "Base object, we dont' want base created ValueType=" + this.ValueType + "; " + "name: " + Name; } } public class StringItem : Item { [JsonProperty("value")] public string Value { get; set; } [JsonProperty("numberChars")] public int NumberCharacters { get; set; } public override string ToString() { return "StringItem object ValueType=" + this.ValueType + ", Value=" + this.Value + "; " + "Num Chars= " + NumberCharacters; } } public class IntItem : Item { [JsonProperty("value")] public int Value { get; set; } public override string ToString() { return "IntItem object ValueType=" + this.ValueType + ", Value=" + this.Value; } } [TestMethod] public void Demo() { // json string var json = "[{\"value\":5,\"valueType\":\"int\",\"valueTypeId\":1,\"name\":\"numberOfDups\"}," + "{\"value\":\"some thing\",\"valueType\":\"string\",\"valueTypeId\":1,\"name\":\"a\",\"numberChars\":11}," + "{\"value\":2,\"valueType\":\"int\",\"valueTypeId\":2,\"name\":\"b\"}]"; var result = JsonConvert.DeserializeObject<List<Item>>(json); Assert.AreEqual("IntItem object ValueType=int, Value=5", result[0].ToString()); Assert.AreEqual("StringItem object ValueType=string, Value=some thing; Num Chars= 11", result[1].ToString()); Assert.AreEqual("IntItem object ValueType=int, Value=2", result[2].ToString()); }