.NET 6中System.Text.Json的七个特性

目录

忽略循环引用序列化和反序列化通知 序列化支持属性排序使用 Utf8jsonWriter 编写 JSONIAsyncEnumerable 支持序列化支持流像 DOM 一样使用 JSON

忽略循环引用

在 .NET 5 中，如果存在循环依赖, 那么序列化的时候会抛出异常, 而在 .NET 6 中, 你可以选择忽略它。

Category dotnet = new(){    Name = ".NET 6",};Category systemTextJson = new(){    Name = "System.Text.Json",    Parent = dotnet};dotnet.Children.Add(systemTextJson);JsonSerializerOptions options = new(){    ReferenceHandler = ReferenceHandler.IgnoreCycles,    WriteIndented = true};string dotnetJson = JsonSerializer.Serialize(dotnet, options);Console.WriteLine($"{dotnetJson}");public class Category{    public string Name { get; set; }    public Category Parent { get; set; }    public List<Category> Children { get; set; } = new();}// 输出:// {//   "Name": ".NET 6",//   "Parent": null,//   "Children": [//     {//       "Name": "System.Text.Json",//       "Parent": null,//       "Children": []//     }//   ]// }

序列化和反序列化通知

在 .NET 6 中，System.Text.Json 公开序列化和反序列化的通知。

有四个新接口可以根据您的需要进行实现：

IJsonOnDeserializedIJsonOnDeserializingIJsonOnSerializedIJsonOnSerializing

Product invalidProduct = new() { Name = "Name", Test = "Test" };JsonSerializer.Serialize(invalidProduct);// The InvalidOperationException is thrownstring invalidJson = "{}";JsonSerializer.Deserialize<Product>(invalidJson);// The InvalidOperationException is thrownclass Product : IJsonOnDeserialized, IJsonOnSerializing, IJsonOnSerialized{    public string Name { get; set; }    public string Test { get; set; }    public void OnSerialized()    {        throw new NotImplementedException();    }    void IJsonOnDeserialized.OnDeserialized() => Validate(); // Call after deserialization    void IJsonOnSerializing.OnSerializing() => Validate();   // Call before serialization    private void Validate()    {        if (Name is null)        {            throw new InvalidOperationException("The 'Name' property cannot be 'null'.");        }    }}

 序列化支持属性排序

在 .NET 6 中, 添加了 JsonPropertyOrderAttribute 特性，允许控制属性的序列化顺序，以前，序列化顺序是由反射顺序决定的。

Product product = new(){    Id = 1,    Name = "Surface Pro 7",    Price = 550,    Category = "Laptops"};JsonSerializerOptions options = new() { WriteIndented = true };string json = JsonSerializer.Serialize(product, options);Console.WriteLine(json);class Product : A{    [JsonPropertyOrder(2)]      public string Category { get; set; }    [JsonPropertyOrder(1)]      public decimal Price { get; set; }    public string Name { get; set; }      [JsonPropertyOrder(-1)]      public int Id { get; set; }}class A{    public int Test { get; set; }}// 输出:// {//   "Id": 1,//   "Name": "Surface Pro 7",//   "Price": 550,//   "Category": "Laptops"// }

使用 Utf8JsonWriter 编写 JSON

.NET 6 增加了 System.Text.Json.Utf8JsonWriter，你可以方便的用它编写原始Json。

JsonWriterOptions writerOptions = new() { Indented = true, };using MemoryStream stream = new();using Utf8JsonWriter writer = new(stream, writerOptions);writer.WriteStartObject();writer.WriteStartArray("customJsonFormatting");foreach (double result in new double[] { 10.2, 10 }){    writer.WriteStartObject();    writer.WritePropertyName("value");    writer.WriteRawValue(FormatNumberValue(result), skipInputValidation: true);    writer.WriteEndObject();}writer.WriteEndArray();writer.WriteEndObject();writer.Flush();string json = Encoding.UTF8.GetString(stream.ToArray());Console.WriteLine(json);static sthttp://www.easck.comring FormatNumberValue(double numberValue){    return numberValue == Convert.ToInt32(numberValue)        ? numberValue.ToString() + ".0"        : numberValue.ToString();}// 输出:// {//    "customJsonFormatting": [//      {//        "value": 10.2//      },//      {//        "value": 10.0//      }//  ]// }

IAsyncEnumerable 支持

在 .NET 6 中， System.Text.Json 支持 IAsyncEnumerable。

static async IAsyncEnumerable<int> GetNumbersAsync(int n){    for (int i = 0; i < n; i++)    {        await Task.Delay(1000);        yield return i;    }}// Serialization using IAsyncEnumerableJsonSerializerOptions options = new() { WriteIndented = true };using Stream 输出Stream = Console.OpenStandard输出();var data = new { Data = GetNumbersAsync(5) };await JsonSerializer.SerializeAsync(输出Stream, data, options);// 输出:// {//    "Data": [//      0,//      1,//      2,//      3,//      4//  ]// }// Deserialization using IAsyncEnumerableusing MemoryStream memoryStream = new(Encoding.UTF8.GetBytes("[0,1,2,3,4]"));// Wraps the UTF-8 encoded text into an IAsyncEnumerable<T> that can be used to deserialize root-level JSON arrays in a streaming manner.await foreach (int item in JsonSerializer.DeserializeAsyncEnumerable<int>(memoryStream)){    Console.WriteLine(item);}// 输出:// 0// 1// 2// 3// 4

IAsyncEnumerable 的序列化的动图。

g in JSON formatstring json = jObject.ToJsonString();Console.WriteLine(json); // {"Value":"Text","Array":[1,5,13,17,2]}

以上所述是小编给大家介绍的.NET 6中System.Text.Json的七个特性，希望对大家有所帮助。在此也非常感谢大家对我们网站的支持！