Custom serializer options for WebApiModule

[simohr]

Is your feature request related to a problem? Please describe.
Hello, since upgrading to embedio version 3.4.3 from version 3.3.3 we have problems with serialization in web controllers. In 3.3.3 we serialize the objects and return them:

public class PersonController : WebApiController
{
    public class Person
    {
        public string Name { get; set; }
    }

    [Route(HttpVerbs.Get, "/person")]
    public string GetPerson()
    {
        return serializer.Serialize(new Person() { Name = "SomeName"});
    }
}

However in 3.4.3 the controller has automatic serialization and we no longer need to use our own. This is a problem for us because the JSON objects created are not what we have defined. For example all properties appear with capital letters and slashes are escaped (''):
Now:

{"Name" : "SomeName"}
{"Url":"http:/\/\localhost:/\port"}

Before:

{"name" : "SomeName"}
{"url":"http:\\localhost:port"}

Describe the solution you'd like
Is there a way to stop the automatic serialization or a way to configure its' settings.

[rdeago]

Hello @simohr, thanks for using EmbedIO!

While we assess where the bug lies exactly (JSON serialization is part of SWAN, so we may need to open an issue there) here's how to return any given string from a Web API method:

    [Route(HttpVerbs.Get, "/person")]
    public void GetPerson()
    {
        Response.ContentType = MimeType.Json;
		using (var writer = HttpContext.OpenResponseText(Encoding.UTF8, true))
        {
            writer.Write(serializer.Serialize(new Person() { Name = "SomeName"}));
        }
    }

Notice that the method has a void return type, to signal that it produces no data to serialize automatically. If you need it to be an async method, return Task instead.

If you omit the second parameter to OpenResponseText:

• the response will not be buffered in memory;
• no Content-Length header will be sent;
• chunked transfer encoding will be used.

This will be usually fine if your client is a browser, but can cause problems if the client relies on the presence of a Content-Length header.

[simohr]

After a little more research we found an alternative solution using the ResponseSerializerCallback. We defined our own callback with the needed settings. Thank you for the response. Here is the solution:
In the code where you define your WithWebApiModule :

 webServer.WithWebApi("/api", SerializationCallback, m => m.WithController(() => new CustomWebApiController(webModule)));

And the SerializationCallback :

        public static async Task SerializationCallback(IHttpContext context, object? data)
        {
            Validate.NotNull(nameof(context), context).Response.ContentType = MimeType.Json;
            using var text = context.OpenResponseText(new UTF8Encoding(false));
            await text.WriteAsync(JsonSerializer.Serialize(data, new JsonSerializerOptions() { PropertyNamingPolicy = JsonNamingPolicy.CamelCase })).ConfigureAwait(false);
        }

[rdeago]

Well done @simohr! It's refreshing to see someone taking advantage of the customizability of EmbedIO v3.

If you want to squeeze out a little more performance, store your serializer options in a static readonly field, so they're ready to use every time. 😉