Compass.NET

Simple HTTP request router for .NET backends

This documentation refers the v6.X of the library

How to use

This library comes with an extremely simple API set (consits of a few methods only)

1. Register the known routes

   using System.Collections.Generic;
   using System.Net;
   
   using Solti.Utils.Router;
   
   RouterBuilder routerBuilder = new
   (
   	// This handler is called on every unknown routes
   	handler: (object? state, HttpStatusCode reason) =>
   	{
   		HttpListenerContext ctx = (HttpListenerContext) state;
   		...
   	},
   	// can be omitted
   	converters: DefaultConverters.Instance
   );
   routerBuilder.AddRoute
   (
   	// A route may contain parameter(s)
   	route: "/get/picture-{id:int}",
   	handler: (IReadOnlyDictionary<string, object?> paramz, object? state) =>
   	{
   		HttpListenerContext ctx = (HttpListenerContext) state;
   		int id = (int) paramz["id"];
   		...
   	},
   	// "GET" is the default
   	"GET", "OPTIONS"
   );

   A valid route looks like [/]segment1/[prefix]{paramName:converter[:style]}[suffix]/segment3[/]

2. Build the router delegate and start the HTTP backend

   Router route = routerBuilder.Build();
   
   HttpListener listener = new HttpListener();
   listener.Prefixes.Add("http://localhost:8080/");
   listener.Start();
   ...
   while (Listener.IsListening)  // probably this will run in a separate thread
   {
   	HttpListenerContext context = Listener.GetContext();
   	route(context, context.Request.Url!.AbsolutePath.AsSpan(), context.Request.HttpMethod.AsSpan());
   }

For a more comprehensive example check out the use cases fixture

Converters

Converters are used to parse variable value coming from the request path. Default converters (int, float, guid, date, str and enum) can be accessed via the DefaultConverters.Instance property.

using System.Collections.Generic;

using Solti.Utils.Router;

RouterBuilder routerBuilder = new
(
	defaultHandler: (object? state) => {...},
	converters: new Dictionary<string, ConverterFactory>(DefaultConverters.Instance)
	{
		{"mytype", static (string? style) => new MyConverter(style)}
	}
);

class MyConverter: IConverter 
{
    public string Id { get; }
    public string? Style { get; }
    public bool ConvertToValue(ReadOnySpan<char> input, out object? value) { ... }
    public bool bool ConvertToString(object? input, out string? value) { ... }
    public MyConverter(string? style)
    {
        Id = $"{GetType().Name}:{style}";
        Style = style;
    }
}

Building routes from template

using System.Collections.Generic;

using Solti.Utils.Router;

RouteTemplateCompiler compile = RouteTemplate.CreateCompiler("http://localhost:8080/get/picture-{id:int}");
string route = compile(new Dictionary<string, object?> { { "id", 1986 } });  // route == "http://localhost:8080/get/picture-1986"
...

Advanced usage

Async routing

In real world, request handlers often contain complex, async logic. AsyncRouterBuilder is aimed to support this use case with an API set very similar to RouterBuilder:

using System.Collections.Generic;
using System.Net;

using Solti.Utils.Router;

AsyncRouterBuilder routerBuilder = AsyncRouterBuilder.Create
(
	handler: async (object? state, HttpStatusCode reason) =>
	{
		HttpListenerContext ctx = (HttpListenerContext) state;
		await ...
	},
	// can be omitted
	converters: DefaultConverters.Instance
);
routerBuilder.AddRoute
(
	route: "/get/picture-{id:int}",
	handler: async (IReadOnlyDictionary<string, object?> paramz, object? state) =>
	{
		HttpListenerContext ctx = (HttpListenerContext) state;
		int id = (int) paramz["id"];
		await ...
	},
	// "GET" is the default
	"GET", "OPTIONS"
);
routerBuilder.AddRoute
(
	route: "/",
	// non-async callbacks also supported
	handler: (IReadOnlyDictionary<string, object?> paramz, object? state) =>
	{
		...
	}
);
AsyncRouter route = routerBuilder.Build();

...

HttpListenerContext context = Listener.GetContext();
object? result = await route(context, context.Request.Url!.AbsolutePath.AsSpan(), context.Request.HttpMethod.AsSpan());

IoC backed routing

Since request handlers may contain complex logic and they usually depend on another services, it's a suggested practice to grab them via dependency injection:

using System.Collections.Generic;
using System.IO;
using System.Net;

using Microsoft.Extensions.DependencyInjection;

using Solti.Utils.Router;

using ResponseData = (HttpStatusCode Status, object? Body);

AsyncRouterBuilder routerBuilder = AsyncRouterBuilder.Create
(
	handler: async (object? state, HttpStatusCode reason) =>
	{
		return new ResponseData(HttpStatusCode.NotFound, "Not found");
	}
);
routerBuilder.AddRoute
(
	route: "/get/picture-{id:int}",
	handler: async (IReadOnlyDictionary<string, object?> paramz, object? state) =>
	{
		IServiceProvider svcProvider = (IServiceProvider) state;
		int id = (int) paramz["id"];

		return await svcProvider.GetService(typeof(PictureStore)).GetPicture(id);
	}
);

...

ServiceCollection services = new();
services.AddScoped<PictureStore>();
ServiceProvider serviceProvider = services.BuildServiceProvider();

...

using(IServiceScope scope = serviceProvider.CreateScope())
{
	HttpListenerContext context = Listener.GetContext();
	object? response = await route(scope.ServiceProvider, context.Request.Url!.AbsolutePath, context.Request.HttpMethod);

	context.Response.ContentType = "application/json";

	if (response is ResponseData responseData)
	{
		context.Response.StatusCode = (int) responseData.Status;
		response = responseData.Body;
	}
	else
	{
		context.Response.StatusCode = (int) HttpStatusCode.OK;
	}

	using (StreamWriter streamWriter = new(context.Response.OutputStream))
	{
		streamWriter.Write(JsonSerializer.Serialize(response));
	}

	context.Response.Close();
}

The Solti.Utils.Router.Extensions namespace aims to simplify the route registration described above:

using Solti.Utils.Router;
using Solti.Utils.Router.Extensions;

routerBuilder.AddRoute<PictureStore>
(
    "/get/picture-{id:int}",
    store => store.GetPicture(default)  // GetPicture() should have only one parameter named "id" 
);

// OR

routerBuilder.AddRoute<PictureStore>
(
    "/get/picture-{id:int}",
    method  // MethodInfo object pointing to GetPicture() 
);

For a more comprehensive example check out the use cases fixture

Error handling

You can register your own (even async) exception handler to be built into the router delegate

using System;

using Solti.Utils.Router;

RouterBuilder routerBuilder = new();
routerBuilder.RegisterExceptionHandler(handler: (object? state, MyException exception) => exception);
routerBuilder.AddRoute("/fail", handler: (IReadOnlyDictionary<string, object?> paramz, object? state) => throw new MyException());

Router route = routerBuilder.Build();

Assert.That(route(null, "/fail", "GET"), Is.InstanceOf<MyException>());

or

using System;

using Solti.Utils.Router;

AsyncRouterBuilder routerBuilder = AsyncRouterBuilder.Create();
routerBuilder.RegisterExceptionHandler(handler: (object? state, MyException exception) => Task.FromResult(exception));
routerBuilder.AddRoute("/fail", handler: (IReadOnlyDictionary<string, object?> paramz, object? state) => Task.FromException<TAny>(new MyException()));

AsyncRouter route = routerBuilder.Build();

Assert.That(await route(null, "/fail", "GET"), Is.InstanceOf<MyException>());

Route parsing

Lets suppose we want to validate route parameters if they meet a given condition. In this case we may utilize the RouteTemplate.Parse() method:

using System.Reflection;
using Solti.Utils.Router;

void Validate(ParameterInfo[] expected, string route)
{
  ParsedRoute parsed = RouteTemplate.Parse(route);
  if (parsed.Parameters.Count != expected.Length)
	throw ...;

  foreach (ParameterInfo param in expected)
  {
     if (!parsed.Parameters.TryGetValue(param.Name, out Type t) || param.Type != t)
	   throw ...;
  }

  ...
}

Resources

• API Docs
• Benchmark Results
• Version History

Supported frameworks

This project currently targets .NET Standard 2.0 and 2.1. and had been tested against net472, netcoreapp3.1, net5.0, net6.0, net7.0 and net8.0.