如何解决System.Text.Json:如何将对象序列化为带有键的嵌套子对象?
我有一个要序列化的以下类的对象:
[Serializable]
public class BuildInfo
{
public DateTime BuildDate { get; set; }
public string BuildVersion { get; set; }
}
我编写了以下方法来序列化任何对象:
...
public static string JsonSerialize<TValue>(TValue value)
{
var options = new JsonSerializerOptions
{
PropertyNamingPolicy = JsonNamingPolicy.CamelCase,WriteIndented = true
};
return JsonSerializer.Serialize(value,options);
}
...
我得到以下输出(示例):
{
"buildDate": "2021-04-22T17:29:59.1611109+03:00","buildVersion": "1.0.1"
}
我想得到这样的输出:
{
"buildInfo": {
"buildDate": "2021-04-22T17:29:59.1611109+03:00","buildVersion": "1.0.1"
}
}
我该怎么做?
解决方法
你可以试试这个
JsonSerialize( new { BuildInfo = build })
编辑
在调用 JsonSerialize 之前处理这个的简单方法是有一个包装类
var buildInfoWrapper = new { BuildInfo = buildInfo };
JsonSerialize(buildInfoWrapper)
,
我花了半天时间,但我做到了。
首先,我们需要定义自定义 JSON 转换器:
public class TopAsNestedJsonConverter<TValue> : JsonConverter<TValue>
{
private readonly string _propertyName;
private readonly JsonSerializerOptions _referenceOptions;
public TopAsNestedJsonConverter(JsonSerializerOptions referenceOptions)
{
_propertyName = FormatPropertyName(typeof(TValue).Name,referenceOptions);
_referenceOptions = referenceOptions;
}
public override TValue? Read(ref Utf8JsonReader reader,Type typeToConvert,JsonSerializerOptions options)
{
var value = default(TValue);
var propertyFound = false;
if (reader.TokenType != JsonTokenType.StartObject)
{
return value;
}
while (reader.Read())
{
switch (reader.TokenType)
{
case JsonTokenType.PropertyName when IsPropertyFound(reader.GetString()):
propertyFound = true;
break;
case JsonTokenType.StartObject when propertyFound:
value = JsonSerializer.Deserialize<TValue>(ref reader,_referenceOptions);
propertyFound = false;
break;
}
}
return value;
}
public override void Write(Utf8JsonWriter writer,TValue? value,JsonSerializerOptions options)
{
writer.WriteStartObject();
writer.WritePropertyName(_propertyName);
JsonSerializer.Serialize(writer,value,_referenceOptions);
writer.WriteEndObject();
}
private bool IsPropertyFound(string? propertyName)
{
return string.Equals(_propertyName,propertyName,_referenceOptions.PropertyNameCaseInsensitive
? StringComparison.OrdinalIgnoreCase
: StringComparison.Ordinal);
}
private static string FormatPropertyName(string propertyName,JsonSerializerOptions options)
{
return options.PropertyNamingPolicy != null
? options.PropertyNamingPolicy.ConvertName(propertyName)
: propertyName;
}
}
然后,我们需要一个实用程序类以方便使用:
public static class JsonUtilities
{
public static string JsonSerializeTopAsNested<TValue>(TValue? value,JsonSerializerOptions? options = null)
{
return JsonSerializer.Serialize(value,GetConverterOptions<TValue>(options));
}
public static async Task<string> JsonSerializeTopAsNestedAsync<TValue>(TValue? value,JsonSerializerOptions? options = null,CancellationToken cancellationToken = default)
{
await using var stream = new MemoryStream();
await JsonSerializer.SerializeAsync(stream,GetConverterOptions<TValue>(options),cancellationToken);
return Encoding.UTF8.GetString(stream.ToArray());
}
public static TValue? JsonDeserializeTopAsNested<TValue>(string json,JsonSerializerOptions? options)
{
return JsonSerializer.Deserialize<TValue>(json,GetConverterOptions<TValue>(options));
}
public static async Task<TValue?> JsonDeserializeTopAsNestedAsync<TValue>(string json,JsonSerializerOptions? options,CancellationToken cancellationToken = default)
{
await using var stream = new MemoryStream(Encoding.UTF8.GetBytes(json));
return await JsonSerializer.DeserializeAsync<TValue>(stream,cancellationToken);
}
private static JsonSerializerOptions GetConverterOptions<TValue>(JsonSerializerOptions? options = null)
{
var referenceOptions = options == null ? new JsonSerializerOptions() : new JsonSerializerOptions(options);
var converterOptions = new JsonSerializerOptions(referenceOptions);
converterOptions.Converters.Add(new TopAsNestedJsonConverter<TValue>(referenceOptions));
return converterOptions;
}
}
最后是示例代码:
public class BuildInfo
{
public DateTime? BuildDate { get; init; }
public string? BuildVersion { get; init; }
}
public static class Program
{
public static async Task Main()
{
var buildInfo = new BuildInfo
{
BuildDate = DateTime.Now,BuildVersion = "1.0.1"
};
var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
{
PropertyNameCaseInsensitive = false,WriteIndented = true
};
var json = await JsonUtilities.JsonSerializeTopAsNestedAsync(buildInfo,options);
Console.WriteLine(json);
var info = await JsonUtilities.JsonDeserializeTopAsNestedAsync<BuildInfo>(json,options);
Console.WriteLine($"{info?.BuildDate} {info?.BuildVersion}");
}
}
如果您在代码或算法本身中发现任何错误,我会很高兴。
,考虑到所有的答案和评论,我得到了以下代码:
public static class JsonUtilities
{
public static string JsonSerializeTopAsNested<TValue>(TValue? value,JsonSerializerOptions? options = null)
{
return JsonSerializer.Serialize(ToSerializableObject(value,options),options);
}
public static async Task<string> JsonSerializeTopAsNestedAsync<TValue>(TValue? value,ToSerializableObject(value,options,cancellationToken);
return Encoding.UTF8.GetString(stream.ToArray());
}
public static TValue? JsonDeserializeTopAsNested<TValue>(string json,JsonSerializerOptions? options = null)
{
var serializableObject = JsonSerializer.Deserialize<Dictionary<string,TValue?>>(json,options);
return FromSerializableObject(serializableObject,options);
}
public static async Task<TValue?> JsonDeserializeTopAsNestedAsync<TValue>(string json,CancellationToken cancellationToken = default)
{
await using var stream = new MemoryStream(Encoding.UTF8.GetBytes(json));
var serializableObject = await JsonSerializer.DeserializeAsync<Dictionary<string,TValue?>>(stream,cancellationToken);
return FromSerializableObject(serializableObject,options);
}
private static Dictionary<string,TValue?> ToSerializableObject<TValue>(TValue? propertyValue,JsonSerializerOptions? options)
{
var propertyName = GetPropertyName<TValue>(options);
return propertyValue == null && options is {IgnoreNullValues: true}
? new Dictionary<string,TValue?>()
: new Dictionary<string,TValue?> {[propertyName] = propertyValue};
}
private static TValue? FromSerializableObject<TValue>(IReadOnlyDictionary<string,TValue?>? serializableObject,JsonSerializerOptions? options)
{
var propertyName = GetPropertyName<TValue>(options);
return serializableObject != null && serializableObject.ContainsKey(propertyName)
? serializableObject[propertyName]
: default;
}
private static string GetPropertyName<TValue>(JsonSerializerOptions? options)
{
var propertyName = typeof(TValue).Name;
return options?.PropertyNamingPolicy?.ConvertName(propertyName) ?? propertyName;
}
}
如果发现更多评论和错误,我将不胜感激。
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