json 从遗留属性名称反序列化
Posted
技术标签:
【中文标题】json 从遗留属性名称反序列化【英文标题】:json deserialize from legacy property names 【发布时间】:2016-01-14 07:40:44 【问题描述】: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对其进行序列化?
编辑:要求是从正在序列化/反序列化的类中删除过时的成员。
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,其中包含一个名称列表,它可能在过去被序列化过。
[DataContract]
class TestObject
[LegacyDataMemberNames("alpha", "omega")]
[DataMember(Name = "a")]
public int A get; set;
我希望始终使用名称“a”进行 json 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
【问题讨论】:
这个问题不应该被关闭。 @Brian Rogers 提出的“类似”问题有一个解决方案,包括让过时的成员留在课堂上。这个问题是关于删除过时的成员。 【参考方案1】:这可以通过扩展DefaultContractResolver
创建的自定义IContractResolver
来完成:
[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
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;
然后将属性添加到您的类型中,如问题所示:
[DataContract]
class TestObject
[LegacyDataMemberNames("alpha", "omega")]
[DataMember(Name = "a")]
public int A get; set;
构造和配置LegacyPropertyResolver
的实例,例如如下:
static IContractResolver legacyResolver = new LegacyPropertyResolver
// Configure as required, e.g.
// NamingStrategy = new CamelCaseNamingStrategy()
;
然后在settings
中使用:
var settings = new JsonSerializerSettings ContractResolver = legacyResolver ;
var deserialized = JsonConvert.DeserializeObject<TestObject>(jsonString, settings);
注意事项:
此实现不要求类具有显式数据协定属性注释。如果您愿意,可以添加该限制。
您应该cache and reuse instances of contract resolvers 以获得最佳性能。
演示小提琴here.
【讨论】:
天哪,哇,这是一个非常彻底的答案。谢谢。【参考方案2】:使用 Json.NET 的一个非常简单的解决方案是仅提供带有 setter 的旧属性。
class TestObject
public int A get; set;
public int alpha set => A = value;
public int omega set => A = value;
您可能宁愿不公开这些,在这种情况下,您只需标记private
并添加JsonProperty
属性。
class TestObject
public int A get; set;
[JsonProperty] private int alpha set => A = value;
[JsonProperty] private int omega set => A = value;
【讨论】:
很好的回答蒂姆【参考方案3】:我采用了您的代码并将其修改为我自己的样式,如下所示:
[System.AttributeUsage(System.AttributeTargets.Property | System.AttributeTargets.Field, AllowMultiple = false, Inherited = true)]
public class LegacyDataMemberNamesAttribute : Attribute
public readonly string[] LegacyNames;
public LegacyDataMemberNamesAttribute(params string[] legacyNames)
LegacyNames = legacyNames;
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."
public static readonly LegacyPropertyResolver Instance = new LegacyPropertyResolver();
protected LegacyPropertyResolver() : base()
protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
var properties = base.CreateProperties(type, memberSerialization);
foreach (var property in properties.ToArray())
if (!property.Writable) continue;
foreach (var legacyName in GetLegacyNames(property))
properties.Add(CloneWithLegacyName(property, legacyName));
return properties;
static IEnumerable<string> GetLegacyNames(JsonProperty property)
return property.AttributeProvider.GetAttributes(typeof(LegacyDataMemberNamesAttribute), true)
.Cast<LegacyDataMemberNamesAttribute>()
.SelectMany(a => a.LegacyNames)
.Distinct();
static readonly object[] _emptyObjectArray = new object[0];
static readonly MethodInfo _propertyClone = typeof(JsonProperty).GetMethod("MemberwiseClone", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
static JsonProperty CloneWithLegacyName(JsonProperty property, string legacyName)
var legacyProperty = (JsonProperty)_propertyClone.Invoke(property, _emptyObjectArray);
legacyProperty.Readable = false;
legacyProperty.PropertyName = legacyName;
return legacyProperty;
【讨论】:
以上是关于json 从遗留属性名称反序列化的主要内容,如果未能解决你的问题,请参考以下文章