File Uploading with ASP Components

Every now and then there comes a time when a web application requires more from a user. It’s not enough that the application receives data in the form of user text boxes and drop-down selections. Sometimes, we need the user to upload a file onto the server. But can we trust the user to setup an FTP program, connect to our server, and place the right file into the right folder without touching anything else? Of course not. What we need to a chimp-simple way to allow users to upload a specific type of file into a specific folder.

Requirements

For this scenario I have 3 requirements:

1. Restrict the user to uploading to a specified directory on my server.
2. Restrict file size to prevent huge files from filling up my disk space.
3. Restrict file types. In this example I only will want image files. Any other file type must be rejected.

Using an ASP Component to Handle File Uploads

There are many file upload components that one can purchase or, if you are so inclined, you can roll your own. The 2 most popular ASP file upload components are Software Artisans FileUp and Persists AspUpload. Both handle uploads slightly different. Let’s code each of these components to handle the above requirements.

The FORM

The FORM, where the client uploads a file, is identical.

<form name="form" action="upload.asp" enctype="MULTIPART/FORM-DATA" method="POST">

 <input type="file" name="file1"> <input type="submit" value="Upload Files"> 

</form>

Shared Code

Before you pick which component you will be using, here is some common code that both can use. isFileSizeOK handles the file size restrictions. isValidFile is where you’ll define what file extensions the client can upload.

intMaxFileSize = 8000
strUploadFolder = "c:\uploadFolder" 

Function isFileSizeOK(bytes)
 ' restrict file byte size    
 byteMAX = intMaxFileSize
 If bytes > byteMAX Then
   isFileSizeOK = FALSE
 Else
   isFileSizeOK = TRUE
 End If 

End Function 

Function isValidFile(filename)
 ' define what file types you will permit to upload    
 fileExtension = lcase(right(filename,4))
 select case fileExtension
   case ".gif",".jpg",".png","jpeg"
     isValidFile = TRUE
   case else
     isValidFile = FALSE
 end select 

End Function

Software Artisans FileUp

Sub uploadSA
 Set up = Server.CreateObject("SoftArtisans.FileUp")
 up.Path = uploadFolder
 If NOT up.IsEmpty Then
   filename = Mid(up.UserFilename, InstrRev(up.UserFilename, "\") + 1)
   ' restrict file types to upload       

   If isValidFile(filename) Then
   ' restrict file by size          
       If isFileSizeOK(up.TotalBytes) Then
         up.Save
         strUploadStatus1 = "File [" & filename & "] Uploaded Successfully! " & up.TotalBytes
       Else
         strUploadStatus1 = "ERROR: File Too Large: " & filename & " (" & up.TotalBytes & " bytes)"
       End If
   Else
      strUploadStatus1 = "ERROR: This File Type is restricted from uploading: " & filename
   End If
 End If
 Set up = Nothing 

End Sub

Persists AspUpload

With AspUpload, you save the file first, then perform checks. If the file fails the checks, then the code deletes it from the server. This component also has a “SaveToMemory” option, which bypasses the write to the disk until instructed. ASPUpload has built-in image size handling and can detect if a file is an image with the .ImageType property, but for this example we’ll use the isValidFile function.

Sub uploadPersists
  Set up = Server.CreateObject("Persits.Upload.1")
  up.OverwriteFiles = TRUE
  up.SetMaxSize intMaxFileSize
  up.Save uploadFolder
  For Each File in up.Files
     fileName = File.ExtractFileName
     If isValidFile(fileName) Then
        If isFileSizeOK(File.OriginalSize) Then
           strUploadStatus2 = "File [" & filename & "] Uploaded Successfully! "
        Else
           strUploadStatus2 = "ERROR: File Too Large: " & fileName & " (" & File.OriginalSize & " bytes)"
           File.Delete
        End If
     Else
        File.Delete
        strUploadStatus2 = "ERROR: This File Type is restricted from uploading: " & fileName
     End If
  Next 

End Sub

Last Words

Both components can do a lot more than what I’ve demonstrated above. For a more complete list of features, check out the online manuals for Persits AspUpload and Software Artisans FileUp.

This tutorial was expanded for DevGuru.com as A Simple ASP File Upload Application.