This article was written in 2001.

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 Persists AspUpload and Software Artisans FileUp.

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

Labels: ASP, COM, Upload, VBscript