ASP.NET Core 3 中是否有使用蛇形大小写作为 JSON 命名策略的内置方式？

Question

我设法使用以下代码使其工作：

.AddNewtonsoftJson(options => {
    options.SerializerSettings.ContractResolver = new DefaultContractResolver
    {
        NamingStrategy = new SnakeCaseNamingStrategy()
    };
});

然而，这使得 MVC 使用Newtonsoft而不是System.Text.JSON更快、异步和内置。

查看命名策略选项中System.Text.JSON我只能找到 CamelCase。是否有对蛇盒的本地支持？什么是实现蛇案例 JSON 命名风格的更好方法？

Answer 1

At the moment there's no builtin support for snake case,
but .NET Core 3.0 allows to set up a custom naming policy by inheriting from JsonNamingPolicy.

You need to implement the ConvertName method with the snake case conversion.
(Newtonsoft Json.NET has an internal StringUtils class which shows how to handle this.)

The POC implementation below, re-uses Json.NET's SnakeCaseNamingStrategy only for the snake case conversion (, whereas the whole application uses System.Text.Json).

It is better to avoid having a dependency on Newtonsoft Json.Net for only the snake case conversion, but in this rather LAZY example below I don't want to rethink/reinvent a snake case conversion method.
The main point of this answer is how to hook a custom policy (and not the snake case conversion itself.) (There are many libraries and code samples that show how to do so.)

public class SnakeCaseNamingPolicy : JsonNamingPolicy
{
    private readonly SnakeCaseNamingStrategy _newtonsoftSnakeCaseNamingStrategy
        = new SnakeCaseNamingStrategy();

    public static SnakeCaseNamingPolicy Instance { get; } = new SnakeCaseNamingPolicy();

    public override string ConvertName(string name)
    { 
        /* A conversion to snake case implementation goes here. */

        return _newtonsoftSnakeCaseNamingStrategy.GetPropertyName(name, false);
    }
}

In Startup.cs you apply this custom SnakeCaseNamingPolicy.

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()            
        .AddJsonOptions(
            options => { 
                options.JsonSerializerOptions.PropertyNamingPolicy = 
                    SnakeCaseNamingPolicy.Instance;
            });
}

An instance of the class below

public class WeatherForecast
{
    public DateTime Date { get; set; }

    public int TemperatureCelcius { get; set; }

    public int TemperatureFahrenheit { get; set; }

    [JsonPropertyName("Description")]
    public string Summary { get; set; }
}

will have a Json representation as:

{ "date" : "2019-10-28T01:00:56.6498885+01:00",
  "temperature_celcius" : 48,
  "temperature_fahrenheit" : 118,
  "Description" : "Cool"
}

Note that the property Summary has been given the name Description,
which matches its System.Text.Json.Serialization.JsonPropertyNameAttribute.

Answer 2

只需稍微修改pfx代码即可消除对Newtonsoft Json.Net.

String扩展 mentod 将给定的字符串转换为SnakeCase.

public static class StringUtils
{
    public static string ToSnakeCase(this string str)
    {
        return string.Concat(str.Select((x, i) => i > 0 && char.IsUpper(x) ? "_" + x.ToString() : x.ToString())).ToLower();
    }
}

然后在我们的SnakeCaseNamingPolicy我们可以做

public class SnakeCaseNamingPolicy : JsonNamingPolicy
{
    public static SnakeCaseNamingPolicy Instance { get; } = new SnakeCaseNamingPolicy();

    public override string ConvertName(string name)
    {
        // Conversion to other naming convention goes here. Like SnakeCase, KebabCase etc.
        return name.ToSnakeCase();
    }
}

最后一步是注册我们的命名政策 Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()            
        .AddJsonOptions(
            options => { 
                options.JsonSerializerOptions.PropertyNamingPolicy = 
                    SnakeCaseNamingPolicy.Instance;
            });
}

使用模型：

public class WeatherForecast
{
    public DateTime Date { get; set; }

    public int TemperatureCelcius { get; set; }

    public int TemperatureFahrenheit { get; set; }

    public string Summary { get; set; }
}

Json 输出：

{
  "date": "2019-10-28T08:26:14.878444+05:00",
  "temperature_celcius": 4,
  "temperature_fahrenheit": 0,
  "summary": "Scorching"
}