如何设置Newtonsoft.Json以使用旧成员名称反序列化对象,但使用当前成员名称序列化该对象?
编辑:一项要求是将过时的成员从要序列化/反序列化的类中删除。
这是一个需要序列化和反序列化的示例对象。我给了一个属性一个属性,该属性包含过去可能已序列化过的名称的列表。
[DataContract] class TestObject { [LegacyDataMemberNames("alpha", "omega")] [DataMember(Name = "a")] public int A { get; set; } }
我想始终使用名称“ a”对json进行序列化,但能够从任何旧名称(包括“ alpha”和“ omega”)以及当前名称“ a”反序列化为一个属性
这可以通过custom来完成,可以IContractResolver通过扩展现有的解析器之一来创建,例如DefaultContractResolver:
IContractResolver
DefaultContractResolver
[System.AttributeUsage(System.AttributeTargets.Property | System.AttributeTargets.Field, AllowMultiple = false, Inherited = true)] public class LegacyDataMemberNamesAttribute : Attribute { public LegacyDataMemberNamesAttribute() : this(new string[0]) { } public LegacyDataMemberNamesAttribute(params string[] names) { this.Names = names; } public string [] Names { get; set; } } public class LegacyPropertyResolver : DefaultContractResolver { // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons. // http://www.newtonsoft.com/json/help/html/ContractResolver.htm // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance." static LegacyPropertyResolver instance; static LegacyPropertyResolver() { instance = new LegacyPropertyResolver(); } public static LegacyPropertyResolver Instance { get { return instance; } } protected LegacyPropertyResolver() : base() { } protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization) { var properties = base.CreateProperties(type, memberSerialization); for (int i = 0, n = properties.Count; i < n; i++) { var property = properties[i]; if (!property.Writable) continue; var attrs = property.AttributeProvider.GetAttributes(typeof(LegacyDataMemberNamesAttribute), true); if (attrs == null || attrs.Count == 0) continue; // Little kludgy here: use MemberwiseClone to clone the JsonProperty. var clone = property.GetType().GetMethod("MemberwiseClone", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public); foreach (var name in attrs.Cast<LegacyDataMemberNamesAttribute>().SelectMany(a => a.Names)) { if (properties.Any(p => p.PropertyName == name)) { Debug.WriteLine("Duplicate LegacyDataMemberNamesAttribute: " + name); continue; } var newProperty = (JsonProperty)clone.Invoke(property, new object[0]); newProperty.Readable = false; newProperty.PropertyName = name; properties.Add(newProperty); } } return properties; } }
请注意,此实现不需要类具有显式的数据协定属性注释。如果愿意,可以添加该限制。
然后将其与以下内容一起使用JsonSerializerSettings:
JsonSerializerSettings
var settings = new JsonSerializerSettings { ContractResolver = LegacyPropertyResolver.Instance };
例如:
[DataContract] class TestObject { [LegacyDataMemberNames("alpha", "omega")] [DataMember(Name = "a")] public int A { get; set; } } public static class JsonExtensions { public static void RenameProperty(this JObject obj, string oldName, string newName) { if (obj == null) throw new NullReferenceException(); var property = obj.Property(oldName); if (property != null) { property.Replace(new JProperty(newName, property.Value)); } } } public class TestClass { public static void Test() { try { TestInner(); } catch (Exception ex) { Debug.Assert(false, ex.ToString()); // No assert throw; } } public static void TestInner() { var test = new TestObject { A = 42 }; var settings = new JsonSerializerSettings { ContractResolver = LegacyPropertyResolver.Instance }; var json = JObject.FromObject(test, JsonSerializer.CreateDefault(settings)); if (json.SelectToken("alpha") != null || json.SelectToken("omega") != null) throw new InvalidOperationException("Failed serialization"); Test(test, json); json.RenameProperty("a", "alpha"); Test(test, json); json.RenameProperty("alpha", "omega"); Test(test, json); } private static void Test(TestObject test, JObject json) { var test1 = json.ToObject<TestObject>(JsonSerializer.CreateDefault(new JsonSerializerSettings { ContractResolver = LegacyPropertyResolver.Instance })); if (test1.A != test.A) throw new InvalidOperationException("Failed deserialization"); Console.WriteLine("Successfully deserialized: " + json.ToString(Formatting.None)); Debug.WriteLine("Successfully deserialized: " + json.ToString(Formatting.None)); } }