.Net Core TimeSpan使用System.Text.Json 反/序列化

向右看齐 2022-12-19 04:00 227阅读 0赞

目前在.Net Core 3.X 新出了个内置的 JSON 库, `System.Text.Json` 性能更高占用内存更少，减少第三方依赖项, 还能规避多个依赖项的依赖 Newtonsoft.Json 版本不一致的问题

但是，凡是都有个但是，`System.Text.Json`目前无法反/序列化转换`TimeSpan`

但从 .NET 5 的 [Milestone][]可以知道，這功能将会包含在 .NET 5 之中，在此之前，如果要对`TimeSpan`做反/序列化转换，可以使用 JsonConverter 来处理。

根据官方 [ .NET发布计划][.NET]，.Net 5 将会在 2020 年 11 月发布，所以这中作法很可能到那时候，就再也不需要了。

## 添加JsonTimeSpanConverter ##

直接在 `System.Text.Json.Serialization`命名空间下，继承自`JsonConverter<TimeSpan>`创建一个可以用来转换 `TimeSpan`  
的 `JsonConverter`  
代码如下：

public class JsonTimeSpanConverter : JsonConverter<TimeSpan>
    {
        public override TimeSpan Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType != JsonTokenType.String)
                throw new NotSupportedException();
            if (typeToConvert != typeof(TimeSpan))
                throw new NotSupportedException();
            // 使用常量 "c" 來指定用 [-][d.]hh:mm:ss[.fffffff] 作为 TimeSpans 转换的格式
            return TimeSpan.ParseExact(reader.GetString(), "c", CultureInfo.InvariantCulture);
        }
        public override void Write(Utf8JsonWriter writer, TimeSpan value, JsonSerializerOptions options)
        {
            writer.WriteStringValue(value.ToString("c", CultureInfo.InvariantCulture));
        }
    }

## 使用方式 ##

只要在类型 `TimeSpan的属性上面`，加上`[JsonConverter(typeof(JsonTimeSpanConverter))]`，这样 `JsonSerializer`在做反/序列化转换时，就会使用我们添加的 `JsonTimeSpanConverter`来做转换。

这样就可以正常反/序列化转换了

### 测试 ###

不标记\[JsonConverter(typeof(JsonTimeSpanConverter))\]

public class TasksOprions
    {
        public int Id { get; set; }
    
        //[JsonConverter(typeof(JsonTimeSpanConverter))]
        public TimeSpan StartTime { get; set; }
    
        //[JsonConverter(typeof(JsonTimeSpanConverter))]
        public TimeSpan EndTime { get; set; }
    }
    static void Main(string[] args)
    {    
        var tasks = new TasksOprions()
        {
            Id=1,
            StartTime = new TimeSpan(1, 0, 0),
            EndTime = new TimeSpan(12, 0, 0)
        };
        var json = JsonSerializer.Serialize(tasks);
        Console.WriteLine(json);
        //输出 
        //{"Id":1,"StartTime":{"Ticks":36000000000,"Days":0,"Hours":1,"Milliseconds":0,"Minutes":0,"Seconds":0,"TotalDays":0.041666666666666664,"TotalHours":1,"TotalMilliseconds":3600000,"TotalMinutes":60,"TotalSeconds":3600},"EndTime":{"Ticks":432000000000,"Days":0,"Hours":12,"Milliseconds":0,"Minutes":0,"Seconds":0,"TotalDays":0.5,"TotalHours":12,"TotalMilliseconds":43200000,"TotalMinutes":720,"TotalSeconds":43200}}
        var obj = JsonSerializer.Deserialize<TasksOprions>(json);
        //obj.Id            1
        //obj.StartTime     { 00:00:00}
        //obj.EndTime	    {00:00:00}
        //反序列化之后TimeSpan类型都是00:00:00
    
        Console.WriteLine(JsonSerializer.Serialize(obj));
        //{"Id":1,"StartTime":{"Ticks":0,"Days":0,"Hours":0,"Milliseconds":0,"Minutes":0,"Seconds":0,"TotalDays":0,"TotalHours":0,"TotalMilliseconds":0,"TotalMinutes":0,"TotalSeconds":0},"EndTime":{"Ticks":0,"Days":0,"Hours":0,"Milliseconds":0,"Minutes":0,"Seconds":0,"TotalDays":0,"TotalHours":0,"TotalMilliseconds":0,"TotalMinutes":0,"TotalSeconds":0}}
    	
    	Console.ReadLine();
    }

标记\[JsonConverter(typeof(JsonTimeSpanConverter))\]

public class TasksOprions
    {
        public int Id { get; set; }
    
        [JsonConverter(typeof(JsonTimeSpanConverter))]
        public TimeSpan StartTime { get; set; }
    
        [JsonConverter(typeof(JsonTimeSpanConverter))]
        public TimeSpan EndTime { get; set; }
    }
    static void Main(string[] args)
    {
        var tasks = new TasksOprions()
        {
            Id=1,
            StartTime = new TimeSpan(1, 0, 0),
            EndTime = new TimeSpan(12, 0, 0)
        };
        var json = JsonSerializer.Serialize(tasks);
        Console.WriteLine(json);
        //输出 
        //{"Id":1,"StartTime":"01:00:00","EndTime":"12:00:00"}
        var obj = JsonSerializer.Deserialize<TasksOprions>(json);
        //obj.Id            1
        //obj.StartTime     {01:00:00}
        //obj.EndTime	    {12:00:00} 
        //反序列化之后和之前的一样的
    
        Console.WriteLine(JsonSerializer.Serialize(obj));
        //{"Id":1,"StartTime":"01:00:00","EndTime":"12:00:00"}
    }

OK，达到效果。

[Milestone]: https://www.colabug.com/goto/aHR0cHM6Ly9naXRodWIuY29tL2RvdG5ldC9ydW50aW1lL21pbGVzdG9uZS83
[.NET]: https://www.colabug.com/goto/aHR0cHM6Ly9naXRodWIuY29tL2RvdG5ldC9jb3JlL2Jsb2IvbWFzdGVyL3JvYWRtYXAubWQ=