使用多态反序列化JSON类，而类型信息json.net [英] Deserializing polymorphic json classes without type information using json.net

问题描述

这 Imgur API调用包含返回一个列表既图库图片和图库专辑类重新以JSON psented $ p $。

This Imgur api call returns a list containing both Gallery Image and Gallery Album classes represented in json.

我看不到如何反序列化这些自动使用Json.NET因为没有$ type属性，告诉它的类是为了重新presented解串器。有一种称为可用于在两者之间区分IsAlbum属性。

I cant see how to deserialize these automatically using Json.NET given that there is no $type property telling the deserializer which class is meant to be represented. There is a property called "IsAlbum" that can be used to differentiate between the two.

<一个href=\"http://stackoverflow.com/questions/16519893/deserialize-json-object-to-polymorphic-c-sharp-object-without-typenamehandling\">This问题似乎显示一个方法，但它看起来像一个黑客攻击的一位。

This question appears to show one method but it looks like a bit of a hack.

如何去反序列化这些类？ （使用C＃，Json.NET）的

How do I go about deserializing these classes? (using C#, Json.NET).

样本数据：

图库

{
    "id": "OUHDm",
    "title": "My most recent drawing. Spent over 100 hours.",
        ...
    "is_album": false
}

图库专辑

{
    "id": "lDRB2",
    "title": "Imgur Office",
    ...
    "is_album": true,
    "images_count": 3,
    "images": [
        {
            "id": "24nLu",
            ...
            "link": "http://i.imgur.com/24nLu.jpg"
        },
        {
            "id": "Ziz25",
            ...
            "link": "http://i.imgur.com/Ziz25.jpg"
        },
        {
            "id": "9tzW6",
            ...
            "link": "http://i.imgur.com/9tzW6.jpg"
        }
    ]
}

}

推荐答案

您可以通过创建一个自定义的 JsonConverter 来处理对象实例化做到这一点很容易。假设你有你的类定义是这样的：

You can do this fairly easily by creating a custom JsonConverter to handle the object instantiation. Assuming you have your classes defined something like this:

public abstract class GalleryItem
{
    public string id { get; set; }
    public string title { get; set; }
    public string link { get; set; }
    public bool is_album { get; set; }
}

public class GalleryImage : GalleryItem
{
    // ...
}

public class GalleryAlbum : GalleryItem
{
    public int images_count { get; set; }
    public List<GalleryImage> images { get; set; }
}

您可以创建转换器是这样的：

You would create the converter like this:

public class GalleryItemConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return typeof(GalleryItem).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, 
        Type objectType, object existingValue, JsonSerializer serializer)
    {
        JObject item = JObject.Load(reader);
        if (item["is_album"].Value<bool>())
        {
            return item.ToObject<GalleryAlbum>();
        }
        else
        {
            return item.ToObject<GalleryImage>();
        }
    }

    public override void WriteJson(JsonWriter writer, 
        object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

下面是显示在行动转换器的示例程序：

Here's an example program showing the converter in action:

class Program
{
    static void Main(string[] args)
    {
        string json = @"
        [
            {
                ""id"": ""OUHDm"",
                ""title"": ""My most recent drawing. Spent over 100 hours."",
                ""link"": ""http://i.imgur.com/OUHDm.jpg"",
                ""is_album"": false
            },
            {
                ""id"": ""lDRB2"",
                ""title"": ""Imgur Office"",
                ""link"": ""http://alanbox.imgur.com/a/lDRB2"",
                ""is_album"": true,
                ""images_count"": 3,
                ""images"": [
                    {
                        ""id"": ""24nLu"",
                        ""link"": ""http://i.imgur.com/24nLu.jpg""
                    },
                    {
                        ""id"": ""Ziz25"",
                        ""link"": ""http://i.imgur.com/Ziz25.jpg""
                    },
                    {
                        ""id"": ""9tzW6"",
                        ""link"": ""http://i.imgur.com/9tzW6.jpg""
                    }
                ]
            }
        ]";

        List<GalleryItem> items = 
            JsonConvert.DeserializeObject<List<GalleryItem>>(json,
                new GalleryItemConverter());

        foreach (GalleryItem item in items)
        {
            Console.WriteLine("id: " + item.id);
            Console.WriteLine("title: " + item.title);
            Console.WriteLine("link: " + item.link);
            if (item.is_album)
            {
                GalleryAlbum album = (GalleryAlbum)item;
                Console.WriteLine("album images (" + album.images_count + "):");
                foreach (GalleryImage image in album.images)
                {
                    Console.WriteLine("    id: " + image.id);
                    Console.WriteLine("    link: " + image.link);
                }
            }
            Console.WriteLine();
        }
    }
}

这是上面程序的输出：

id: OUHDm
title: My most recent drawing. Spent over 100 hours.
link: http://i.imgur.com/OUHDm.jpg

id: lDRB2
title: Imgur Office
link: http://alanbox.imgur.com/a/lDRB2
album images (3):
    id: 24nLu
    link: http://i.imgur.com/24nLu.jpg
    id: Ziz25
    link: http://i.imgur.com/Ziz25.jpg
    id: 9tzW6
    link: http://i.imgur.com/9tzW6.jpg

这篇关于使用多态反序列化JSON类，而类型信息json.net的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！