使用 System.Text.Json 反序列化 Json 时间戳

Question

我正在尝试反序列化以下 JSON

{"serverTime":1613967667240}

变成下面的一个对象class

public class ApiServerTime
{
    [JsonPropertyName("serverTime")]
    public DateTime ServerTime
    {
        get;
        private set;
    }
}

使用以下命令：

JsonSerializer.Deserialize<ApiServerTime>(jsonString);

但生成的对象包含 ServerTime == DateTime.MinValue。我做错了什么？

Answer 1

根据 What is the “right” JSON date format? 你最好使用 ISO 8601

"\"\/Date(1335205592410)\/\""         .NET JavaScriptSerializer
"\"\/Date(1335205592410-0500)\/\""    .NET DataContractJsonSerializer
"2012-04-23T18:25:43.511Z"              JavaScript built-in JSON object
"2012-04-21T18:25:43-05:00"             ISO 8601

你也可以使用 JsonMicrosoftDateTimeConverter 来反序列化它。但它需要更改 json 演示文稿。你可以参考 link System.Text.Json DateTime & DateTimeOffset “/Date()/” serialization

{
    "Date": "\/Date(1580803200000-0800)\/"
}

最后，你可以使用临时模型保存当前时间戳，然后转换它。

public class ApiServerTime{
public long ServerTime{get;set;}
public static DateTime UnixTimeStampToDateTime( double unixTimeStamp )
{
    // Unix timestamp is seconds past epoch
    System.DateTime dtDateTime = new DateTime(1970,1,1,0,0,0,0,System.DateTimeKind.Utc);
    dtDateTime = dtDateTime.AddSeconds( unixTimeStamp ).ToLocalTime();
    return dtDateTime;
}
}

Answer 2

您也可以为 System.Text.Json 注册自定义日期格式化程序。 https://docs.microsoft.com/en-us/dotnet/standard/datetime/system-text-json-support

public class DateTimeConverterForCustomStandardFormatR : JsonConverter<DateTime>
{
    public override DateTime Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return DateTime.UnixEpoch.AddMilliseconds(reader.GetInt64());
    }

    public override void Write(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options)
    {
        // The "R" standard format will always be 29 bytes.
        Span<byte> utf8Date = new byte[29];

        bool result = Utf8Formatter.TryFormat(value, utf8Date, out _, new StandardFormat('R'));
        Debug.Assert(result);

        writer.WriteStringValue(utf8Date);
    }
}


string js = "{\"ServerTime\":1613967667240}";
JsonSerializerOptions options = new JsonSerializerOptions();
options.Converters.Add(new DateTimeConverterForCustomStandardFormatR());
var value = JsonSerializer.Deserialize<ApiServerTime>(js, options);

Answer 3

本着构建更好的鼠标陷阱的精神，这里有一个实现支持..

以秒或毫秒为单位的 Unix 时间。假设：秒 < 9999 年（DateTime 最大值）和毫秒 > 1978.
可为空的日期时间

public class UnixToNullableDateTimeConverter : JsonConverter<DateTime?>
{
    public override bool HandleNull => true;
    public bool? IsFormatInSeconds { get; set; } = null;

    public override DateTime? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TryGetInt64(out var time))
        {
            // if 'IsFormatInSeconds' is unspecified, then deduce the correct type based on whether it can be represented in the allowed .net DateTime range
            if (IsFormatInSeconds == true || IsFormatInSeconds == null && time > _unixMinSeconds && time < _unixMaxSeconds)
                return DateTimeOffset.FromUnixTimeSeconds(time).LocalDateTime;
            return DateTimeOffset.FromUnixTimeMilliseconds(time).LocalDateTime;
        }

        return null;
    }

    public override void Write(Utf8JsonWriter writer, DateTime? value, JsonSerializerOptions options) => throw new NotSupportedException();

    private static readonly long _unixMinSeconds = DateTimeOffset.MinValue.ToUnixTimeSeconds() - DateTimeOffset.UnixEpoch.ToUnixTimeSeconds(); // -62_135_596_800
    private static readonly long _unixMaxSeconds = DateTimeOffset.MaxValue.ToUnixTimeSeconds() - DateTimeOffset.UnixEpoch.ToUnixTimeSeconds(); // 253_402_300_799
}

使用 System.Text.Json 反序列化 Json 时间戳

Deserialise Json Timestamp with System.Text.Json

c#

datetime

json

system.text.json