A WebServer for MonoTouch that also parses posted form data (HttpListenerRequest)

-

I found a few examples of web servers for MonoTouch but none of them parsed the data sent in a POST request.  I looked around the web and was unable to find any examples of how to achieve this.  So now that I’ve written it myself I’ve decided to share my own implementation.  This includes not only the code for processing the form post data but also for registering request handlers etc.

Here is an example of how you would use the web server 

     public BookUploadViewController() 
       : base("BookUploadViewController", null)
     {
       RequestHandler = new DefaultRequestHandler();
       var defaultActionHandlerFactory = new DefaultActionHandlerFactory();
       RegisterActionHandlers(defaultActionHandlerFactory);
       RequestHandler.AddActionHandlerFactory(defaultActionHandlerFactory);
       
       WebServer = new EmbeddedWebServer(RequestHandler);
     }
     
     void RegisterActionHandlers(DefaultActionHandlerFactory factory)
     {
       factory.RegisterHandler(
         request => request.RawUrl == "/",
         request => new IndexActionHandler(request)
         );
       factory.RegisterHandler(
         request => 
           string.Compare(request.RawUrl, "/Upload", true) == 0 && 
           string.Compare(request.HttpMethod, "POST", true) == 0,
         request => new UploadActionHandler(request)
         );
     }
     
     public override void ViewDidAppear(bool animated)
     {
       base.ViewDidAppear(animated);
       StatusLabel.Text = string.Format("Server listening on\r\nhttp://{0}:8080", GetIPAddress ());
       WebServer.Start(8080);
     }
     
     public override void ViewDidDisappear (bool animated)
     {
       base.ViewDidDisappear(animated);
       WebServer.Stop();
     }



And here are two app specific examples of request handlers



 class IndexActionHandler : DefaultActionHandler
 {
   public IndexActionHandler(HttpListenerRequest request)
     : base(request)
   {
   }
   
   public override ActionResult Execute()
   {
     var result = new HtmlResult();
     result.AppendLine("<html>");
     result.AppendLine("<body>");
     result.AppendLine("<h1>Upload an image</h1>");
     result.AppendLine("<form action='/Upload' enctype='multipart/form-data' method='post'>");
     result.AppendLine ("<input name='Image' type='file'/><br/>");
     result.AppendLine("<input name='Upload' type='submit' text='Upload'/>");
     result.AppendLine("</form>");
     result.AppendLine("</body>");
     result.AppendLine("</html>");
     return result;
   }
 }
 
 class UploadActionHandler : DefaultActionHandler
 {
   public UploadActionHandler(HttpListenerRequest request)
     : base(request)
   {
   }
 
   public override ActionResult Execute()
   {
     string errorMessage = null;
     var file = FormData.GetFile("Image");
     if (file == null 
       || file.FileData == null 
       || file.FileData.Length == 0 
       || string.IsNullOrEmpty(file.FileName))
       errorMessage = "No image uploaded";
     
     if (errorMessage == null)
       ProcessFile(file);
       
     var result = new HtmlResult();
     result.AppendLine("<html>");
     result.AppendLine("<body>");
     if (errorMessage == null)
       result.AppendLine("<h1>File uploaded successfully</h1>");
     else
     {
       result.AppendLine("<h1>Error</h1>");
       result.AppendLine("<h2>" + errorMessage + "</h2>");
     }
     result.AppendLine("</body>");
     result.AppendLine("</html>");
     return result;
   }
   
   void ProcessFile(MultiPartStreamFileValue postedFile)
   {
     string fileName = "Where to save the file";
     using (var fileStream = 
       new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None))
     {
       fileStream.Write(postedFile.FileData, 0, postedFile.FileData.Length);
     }
   }
 }


You can download the source code here

Comments

Post a Comment

Popular posts from this blog

Connascence

-
I’ve just finished reading What every programmer should know about object oriented design . The first couple of sections are a bit useless really, but the 3rd section is very good. I particularly liked the section on the difference types of connascence in software. There’s some basic information about it here if you fancy a brief overview of what it is about. It’s a really good book, I recommend you read it! Should only take a day if you only read the 3rd section.
Read more

Convert absolute path to relative path

-
Today I needed to convert an absolute path to a relative path based on a specified base path. E.g. c:\a\b\c -> c:\a\b\c\d\file.txt = d\file.txt c:\a\b\c -> c:\a\file.txt = ..\..\file.txt c:\a\b\c -> c:\a\x\file.txt = ..\..\x\file.txt I am surprised there is nothing in the .NET framework so I had a hunt around and converted the code from the following URL ( http://www.vergentsoftware.com/blogs/ckinsman/default.aspx?date=2006-08-07 ) into C#.... private string RelativePath(string absolutePath, string relativeTo) { string[] absoluteDirectories = absolutePath.Split('\\'); string[] relativeDirectories = relativeTo.Split('\\'); //Get the shortest of the two paths int length = absoluteDirectories.Length < relativeDirectories.Length ? absoluteDirectories.Length : relativeDirectories.Length; //Use to determine where in the loop we exited int lastCommonRoot = -1; int i
Read more

Printing bitmaps using CPCL

-
I've had no end of grief trying to print a PCX to a Zebra Printer using the CPCL printer language. Silly me, didn't notice the EG command (expanded graphics) so there was no need to convert my BMP to a PCX and then struggle with binary data. I still had a bit of grief working out how to print using the EG command because the documentation is quite frankly crap. The expected command format is EG {WidthInBytes} {HeightInPixels} {XPos} {YPos} {Data}\r\n The printer expects a 1 bit pixel matrix. So if pixel(0, 0) is set you will set "80" in the data. If pixel(0, 0) is set and pixel (7, 0) is also set you would sent "81". Basically what you need to do is to read each set of 8 horizontal pixels and then use bit operations to create a byte value 0..255, and then output this as hex 00..FF. Here's the routine :-) public void DrawBitmap(Bitmap bmp, int xPosition, int yPosition) { if (bmp == null) throw new ArgumentNullException("bmp");
Read more