为什么Json.net不使用自定义的IsoDateTimeConverter?
我使用为什么Json.net不使用自定义的IsoDateTimeConverter?,datetime,json.net,converter,Datetime,Json.net,Converter,我使用Json.net来序列化我的对象,我想定制DateTime输出: 下面是一个小例子: [DataContract] class x { [DataMember] [JsonConverter(typeof(IsoDateTimeConverter))] public DateTime datum = new DateTime(1232, 3, 23); } var dtc = new IsoDateTimeConverter(); dtc.DateTimeForm
Json.net
来序列化我的对象,我想定制DateTime
输出:
下面是一个小例子:
[DataContract]
class x
{
[DataMember]
[JsonConverter(typeof(IsoDateTimeConverter))]
public DateTime datum = new DateTime(1232, 3, 23);
}
var dtc = new IsoDateTimeConverter();
dtc.DateTimeFormat = "yy";
JsonConvert.SerializeObject(new x(), dtc);
结果是{“datum”:“1232-03-23T00:00:00”}
而不是{“datum”:“1232”}
这可以正常工作(返回“32”
):
捕获项在哪里?捕获项是通过
[JsonConverter(typeof(IsoDateTimeConverter))]应用的转换器。
取代传递到序列化程序中的转换器。这记录在:
指定哪个
用于转换对象
属性可以放置在类或成员上。当放置在
类,则该属性指定的JsonConverter将是
序列化该类的默认方式。当属性位于
字段或属性,则指定的JsonConverter将始终为
用于序列化该值
使用JsonConverter的优先级是member属性,然后
类属性,最后是传递给
JsonSerializer.
作为一种解决方法,在应用转换器的ReadJson()
和WriteJson()
方法中,可以在序列化程序的转换器列表中检查相关的转换器,如果找到,就使用它。装饰器模式可用于将此逻辑与底层转换逻辑分离。首先,介绍:
public class OverridableJsonConverterDecorator : JsonConverterDecorator
{
public OverridableJsonConverterDecorator(Type jsonConverterType) : base(jsonConverterType) { }
public OverridableJsonConverterDecorator(JsonConverter converter) : base(converter) { }
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
foreach (var converter in serializer.Converters)
{
if (converter == this)
{
Debug.WriteLine("Skipping identical " + converter.ToString());
continue;
}
if (converter.CanConvert(value.GetType()) && converter.CanWrite)
{
converter.WriteJson(writer, value, serializer);
return;
}
}
base.WriteJson(writer, value, serializer);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
foreach (var converter in serializer.Converters)
{
if (converter == this)
{
Debug.WriteLine("Skipping identical " + converter.ToString());
continue;
}
if (converter.CanConvert(objectType) && converter.CanRead)
{
return converter.ReadJson(reader, objectType, existingValue, serializer);
}
}
return base.ReadJson(reader, objectType, existingValue, serializer);
}
}
public abstract class JsonConverterDecorator : JsonConverter
{
readonly JsonConverter converter;
public JsonConverterDecorator(Type jsonConverterType) : this((JsonConverter)Activator.CreateInstance(jsonConverterType)) { }
public JsonConverterDecorator(JsonConverter converter)
{
if (converter == null)
throw new ArgumentNullException();
this.converter = converter;
}
public override bool CanConvert(Type objectType)
{
return converter.CanConvert(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
return converter.ReadJson(reader, objectType, existingValue, serializer);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
converter.WriteJson(writer, value, serializer);
}
public override bool CanRead { get { return converter.CanRead; } }
public override bool CanWrite { get { return converter.CanWrite; } }
}
然后,在IsoDateTimeConverter
顶部应用修饰符,如下所示:
[DataContract]
class x
{
[DataMember]
[JsonConverter(typeof(OverridableJsonConverterDecorator), typeof(IsoDateTimeConverter))]
public DateTime datum = new DateTime(1232, 3, 23);
}
现在,静态应用转换器将根据需要被取代。样品
注意,对于这个特定的测试用例,“截止日期”默认情况下在ISO中序列化,不再需要IsoDateTimeConverter
。强制以特定格式序列化日期可以通过设置:
样品。然而,一般性问题值得回答
[DataContract]
class x
{
[DataMember]
[JsonConverter(typeof(OverridableJsonConverterDecorator), typeof(IsoDateTimeConverter))]
public DateTime datum = new DateTime(1232, 3, 23);
}
[DataContract]
class x
{
[DataMember]
public DateTime datum = new DateTime(1232, 3, 23);
}
var settings = new JsonSerializerSettings { DateFormatString = "yy" };
var json1 = JsonConvert.SerializeObject(new x(), settings);
Console.WriteLine(json1); // Prints {"datum":"32"}
var json2 = JsonConvert.SerializeObject(new x());
Console.WriteLine(json2); // Prints {"datum":"1232-03-23T00:00:00"}