URL mapping with C# HttpListener

Question

In the code below I'm waiting for any call to the 8080 port.

static void Main()
{
  HttpListener listener = new HttpListener();
  listener.Prefixes.Add("http://*:8080/");
  listener.Start();
  while(isRunning)
  {
     HttpListenerContext ctx = listener.GetContext();
     new Thread(new Worker(ctx).ProcessRequest).Start();
  }
}

Is it possible to map specific URL patterns to different behaviour? I want achieve a REST-style server i.e. a call to localhost:8080/person/1 will launch getPersonHandler(int)

[Mapping("*:8080/person/$id")]
public void getPersonHandler(int id){...}

The Mapping syntax is just my own wishful analogy to JAX-RS libraries that I know. I'd like to do the same in C# (desktop C#, not asp)

Answer 1

If you are working in .NET 4.0 or higher and looking for a pre-existing REST server solution that you can plug into (which it sounds like you are), you might want to check out Grapevine. You can get it using NuGet, and the project wiki has lots of sample code. Plus, it is open source, so if you just wanted to see how it can be accomplished, you can see all the source code there.

You can filter requests by path info (using regular expressions) and request methods (GET, POST, etc.).

I am the project author, and I had a similar need as the one you described. Using resources I found here and elsewhere, I built Grapevine so that I would have a solution in my back pocket whenever I needed it again (DRY).

Answer 2

You can get a similar effect without attributes

HttpListener listener = new HttpListener();
listener.Prefixes.Add("http://*:8080/");
listener.Start();
while (true)
{
    HttpListenerContext ctx = listener.GetContext();
    ThreadPool.QueueUserWorkItem((_) =>
    {
        string methodName = ctx.Request.Url.Segments[1].Replace("/", "");
        string[] strParams = ctx.Request.Url
                                .Segments
                                .Skip(2)
                                .Select(s=>s.Replace("/",""))
                                .ToArray();


        var method = this.GetType().GetMethod(methodName);
        object[] @params = method.GetParameters()
                            .Select((p, i) => Convert.ChangeType(strParams[i], p.ParameterType))
                            .ToArray();

        object ret = method.Invoke(this, @params);
        string retstr = JsonConvert.SerializeObject(ret);
    });

Usage would be:

http://localhost:8080/getPersonHandler/333

if you really want to use Attributes then

HttpListener listener = new HttpListener();
listener.Prefixes.Add("http://*:8080/");
listener.Start();
while (true)
{
    HttpListenerContext ctx = listener.GetContext();
    ThreadPool.QueueUserWorkItem((_) =>
    {
        string methodName = ctx.Request.Url.Segments[1].Replace("/", "");
        string[] strParams = ctx.Request.Url
                                .Segments
                                .Skip(2)
                                .Select(s=>s.Replace("/",""))
                                .ToArray();

        var method = this.GetType()
                            .GetMethods()
                            .Where(mi => mi.GetCustomAttributes(true).Any(attr => attr is Mapping && ((Mapping)attr).Map == methodName))
                            .First();

        object[] @params = method.GetParameters()
                            .Select((p, i) => Convert.ChangeType(strParams[i], p.ParameterType))
                            .ToArray();

        object ret = method.Invoke(this, @params);
        string retstr = JsonConvert.SerializeObject(ret);
    });
}

Then you can use as http://localhost:8080/Person/333 and your definitions would be

class Mapping : Attribute
{
    public string Map;
    public Mapping(string s)
    {
        Map = s;
    }
}

[Mapping("Person")]
public void getPersonHandler(int id)
{
    Console.WriteLine("<<<<" + id);
}