Restricting File Types Before Uploading

Restricting File Type and Size Before Uploading

This example shows how to restrict file types and set a maximum file size to upload. We'll use SA-JFile and SA-XFile, Software Artisans' client-side components, instead of restricting at the server level. By restricting the file types on the client side, the inappropriate files will not be uploaded at all.

In both components we'll need to parse, or search through the filenames for the correct file extension. Establishing the maximum size usually means setting a property for the component.

Using SA-JFile

To correctly illustrate the means for restricting the file type, we'll disable the loading of the applet visually. We'll create code that will look through the file collection set before and after adding file(s). Then, we simply set a parameter within the applet tag itself.

Here is the code:

<%@ LANGUAGE="VBSCRIPT" %>
<%
	
	' Get the name of the host machine
	httpHost = Request.ServerVariables("HTTP_HOST") 

	' This is where all the data will be sent
	PostURL = "http://" & httpHost & "/SAfileUpSamples/ClientUpload/restrictTypeSize/JFile/formresp.asp"

%>
<HTML>
<HEAD>
<TITLE>
	SA-JFile Restrict File size and Type Upload Sample
</TITLE>
<script language="Javascript" >
<!--

function add()
{
	if (document.Form1.addFile.value != "")
	{
		document.fileupload.addFile(document.Form1.addFile.value);
		alert(document.Form1.addFile.value + " " + "was added.");
		}
	else   
		{
			alert("No file was added");
		}
	
	
}

function myTransferRestrict()
{
	
	if(SAJFileAppletLoaded)
	{
		
		var file;
		var ext =  new Array() ;
		
		file = document.fileupload.getNumberOfFiles();
		
		ext[0] = "ini"; 
		ext[1] = "txt";
		//ext[2] = "doc";
		
		//Check File Type using restrictFiles function
		restrictFiles(file,ext)
		
		document.fileupload.startUpload();
		
		
	}
	else
		alert("Applet is not loaded.");
}

function restrictFiles( file , ext){
		var typeRes;

		for(i = 0;i < file;i++){ 
			Filename = document.fileupload.getFileNumber(i);
			typeRes = 0
			for(y = 0;y < ext.length;y++){	
				if (Filename.indexOf(ext[y]) == -1){
					typeRes++
					if (typeRes == ext.length && Filename != "") {
						alert(Filename + " " + "will be removed from the file list, since it is not the correct file type.")
						document.fileupload.removeFile(Filename)
						file --;
						i --;
						
					}
				}
			}
			
		}
}


//-->
</script>

</HEAD>

<BODY>

<FORM>

</FORM>

The Java Applet contained in this page can point to files which are located on a users local disk. These default file names can be specified in the Java Applet using applet parameters. The user can also select files using the Java Applet interface.

A function is used to verify the file type by looking at the filename extension.

These files will be submitted to a URL specified as a parameter in the Java applet.

There are two files that have been preset - boot.ini and Autoexec.bat.

This applet will only except ini or doc files and has a file size limit of 1KB.


	<APPLET CODEBASE="/SAJFileSamples" code="softartisans.filetransfer.UploadClient.class" height="0" width="0" mayscript archive="filetransfer.jar" name="fileupload" VIEWASTEXT>
		<PARAM name="cabbase" value="filetransfer.cab">

		<!-- The PostURL is where all the files and form elements will be uploaded to -->
		<PARAM name="PostURL" value="<%=PostURL%>">
		<PARAM name="Filename1" value="c:\boot.ini">
		<PARAM name="Filename2" value="C:\autoexec.bat">
		<PARAM name="HideFileList" value="1">

		<!-- set maxsize-->
		<PARAM name="MaximumFileSize" value="1000">
		
	</APPLET>
<p>
<input type=button value="Verify File Types" onclick="myTransferRestrict()"
</p>

<Form name=Form1>
<BR>
Try to add a file that is not an INI or DOC file.
Add a file:<INPUT type="text" name="addFile">
<input type=button value="Add File" onclick="add()" name="addFilebt">
</Form>
</BODY>
</HTML>

Let's go over some major points of this page:

We use Request.ServerVariables("HTTP_HOST") to supply the name of the web server regardless of where this code is run. This information is passed to the HttpHost variable. HttpHost and PostUrl set the server name and the URL where the file upload will take place.
```
	httpHost = Request.ServerVariables("HTTP_HOST") 
	PostURL = "http://" & httpHost & "/SAfileUpSamples/ClientUpload/restrictTypeSize/JFile/formresp.asp"
```
There are three major functions used:
- add function, which is used in the onclick event of the "addFilebt" button. This function simply adds a file, that has been typed into the addFile text box, into SA-JFile's file collection. If nothing is added, an error message is displayed.
```
function add()
{
	if (window.Form1.addFile.value != "")
	{
		document.fileupload.addFile(window.Form1.addFile.value);
		alert(window.Form1.addFile.value + " " + "was added.");
		}
	else   
		{
			alert("No file was added");
		}
	
	
}
```
- myTransferRestrict function, which detects whether the applet is loaded, sets up the file extensions to check, and starts the transfer progress. If at this time the applet is not loaded, a message displays.
  
  An intrinsic variable to SA-JFile, SAJFileAppletLoaded, is used to detect whether the applet is loaded.
  
  Local variables are then created: file will hold the file collection from the applet and ext will hold the array of extensions to be restricted to for the upload. Only INI and TXT files will be uploaded.
  
  Then the startUpload method is called and then transfer starts.
```
function myTransferRestrict()
{
	
	if(SAJFileAppletLoaded)
	{
		
		var file;
		var ext =  new Array() ;
		
		
		file = document.fileupload.getNumberOfFiles();
		
		ext[0] = "ini"; 
		ext[1] = "txt";
		//ext[2] = "doc";
		
		//Check File Type using restrictFiles function
		restrictFiles(file,ext)
		
		document.fileupload.startUpload();
		
		
	}
	else
		alert("Applet is not loaded.");
}
```
- restrictFiles function, which actually does the parsing of the files and deletes files that are not part of the extension array created.
  
  Two parameters are passed into this function: file for the file collection and ext to hold the array of extensions.
  
  A local variable is created to hold a count of the iteration from the restricted file number.
  
  restrictFiles() goes through the extension array created in the myTransferRestrict function. Then we set an condition to check whether the extension character set exists within the filename. If it does, the typeRes variable is added to itself for the count and then run another condition check to see if the count equals the number extension in the array or if the filename is not blank. If this is true, a message displays stating that the file will be removed from the file collection and then it is removed from the list. Since the file collection is updated immediately, we need to subtract one for total file counts and subtract one for current index. This goes through the file list until there is no more files to check.
```
function restrictFiles( file , ext){
		var typeRes;

		for(i = 0;i < file;i++){ 
			Filename = document.fileupload.getFileNumber(i);
			typeRes = 0
			for(y = 0;y < ext.length;y++){	
				if (Filename.indexOf(ext[y]) == -1){
					typeRes++
					if (typeRes == ext.length && Filename != "") {
						alert(Filename + " " + "will be removed from the file list, since it is not the correct file type.")
						document.fileupload.removeFile(Filename)
						file --;
						i --;
					}
				}
			}
			
		}
```
The next point deals with the applet tag that contains the parameters on the applet. We are setting where the cab file can be located, where the response/upload page is, two file to preset, hide the applet's GUI, use sockets for the transfer connection and finally set the maximum file size for the transfer.

Most of the work in the example comes from getting the file collection from SA-JFile and searching for the file extensions to restricting the files to be uploaded.

Using SA-XFile

With SA-XFile, The file collection is more straight-forward, but the process is the same. The GUI is also visible.

Let's look at the first page:

<%@ LANGUAGE="VBSCRIPT" %>
<%
	
	' Get the virtual location of file from site 
	Filelocal = Server.MapPath("\SAFileUpSamples\ClientUpload\Restricttypesize\")  

	' This is where all the data will be sent
	PostURL = "/SAfileUpSamples/ClientUpload/restrictTypeSize/SAXfile/formresp2.asp"

%>
<HTML>
<HEAD>
<TITLE>Software Artisans SA-AXFile Restrict Size and Type Upload Sample</TITLE>
<%
'---Copyright (c) 1999, Software Artisans, Inc.
'---Mail: info@softartisans.com   http://www.softartisans.com
%>
</HEAD>
<BODY>
<P><STRONG><FONT color=black size=5>SA-XFile File restrict Size and Type Upload Sample</FONT></STRONG></P>
<P>

<OBJECT classid=CLSID:230C3D02-DA27-11D2-8612-00A0C93EEA3C id=AXFFile 
style="LEFT: 0px; TOP: 0px" codebase = saxfile.cab VIEWASTEXT>
</OBJECT>
</P>


<INPUT type="button" value="Button" id=button2 name=button2 value="Start upload" >
<script language="VBS">
	
    Set XFile = AXFFile.XFRequest
    XFile.Server = "localhost"
    XFile.ObjectName = PostURL
    XFile.MaxFileSize = 500
    
    AXFFile.AddFile "c:\boot.ini"
    AXFFile.AddFile "<%=Filelocal%>" & "\softartlogo.jpg"
	
	
sub button2_onclick()
    'Establish File Collection
    'The files will upload but will not show up in the progress bar
    Set files = AXFFile.Files
	
	'msgbox("File count: " & files.count)
	Dim ext(2)
	ext(0) = "ini"
	ext(1) = "txt"
	ext(2) = "doc"
	
	Dim FileDele
	for each p in files
		for each x in ext
			FExt = mid(p.filename,instrrev(p.filename,".")+1)
			'msgbox(FExt & " " & x)
			'msgbox(Strcomp(FExt,x))
			FileDele = p.filename
			if Strcomp(FExt,x) <> 0 Then
				
				RestCount = RestCount + 1
				
			end if
			
		next
			'msgbox("Count:" & RestCount)
			If RestCount = 3 Then ' number of extensions to restrict to
				msgbox(FileDele & " will be removed from the file list" & vbcrlf _ 
				& "since it is not the correct file type")
				AXFFile.Remove (p.filename)
				
				
			end if	
		RestCount = 0
	next
	
	Call startupload
	
End Sub

sub startupload()
	winstyle = "height=300,width=400,status=no,toolbar=no,menubar=no,location=no"
    window.open "AXFFileProgress.htm",null,winstyle
	AXFFile.Start()
end sub

</SCRIPT>
</BODY>
</HTML>

Let's look at the major sections of interest:

We are using server-side variable to be used later. The FileLocal variable gets virtual path that will be used to upload a jpg file that is located on the site. The PostURL variable sets up the page where the upload will be completed.

<%
	
	' Get the virtual location of file from site 
	Filelocal = Server.MapPath("\SAFileUpSamples\ClientUpload\Restricttypesize\")  

	' This is where all the data will be sent
	PostURL = "/SAfileUpSamples/ClientUpload/restrictTypeSize/SAXfile/formresp2.asp"

%>

Further down we create the SAAXFile object from the SA-XFile cab.

<OBJECT classid=CLSID:230C3D02-DA27-11D2-8612-00A0C93EEA3C id=AXFFile 
style="LEFT: 0px; TOP: 0px" codebase = "saxfile.cab" VIEWASTEXT>
</OBJECT>

We create a button that will be used for firing an subroutine for the restricting of file types and calling the upload function - startupload()
```
<INPUT type="button" value="Button" id=button2 name=button2 value="Start upload" >
```
Now we are establishing the properties that set up the SA-XFile transfer. We call an instance of the Request object and then set the Server. With ObjectName property, we set the web page that will create the upload process. The MaxFileSize property is where we set the max size to be uploaded. The error for the max size is intrinct to the component. We have set this to 500 bytes.

<script language="VBS">
	
    Set XFile = AXFFile.XFRequest
    XFile.Server = "localhost"
    XFile.ObjectName = PostURL
    XFile.MaxFileSize = 500

This is where we preset files to be upload. The second file is from the web site itself. Using the Filelocal variable create at the top, we concatenate the full path of the file.

  
    AXFFile.AddFile "c:\boot.ini"
    AXFFile.AddFile "<%=Filelocal%>"& "\softartlogo.jpg"

This is the onclick event subroutine. This is where we create the file collection and restrict the type by the extension. We first create an instance of the file collection with the Files object. Then an array is created with all of the file type extensions to which we want to restrict the upload. The FileDele variable is set to the filename that will be deleted. There are two iterations that are used for the extension array and the file collection. Within the second iteration we get the extension of the file from the list. We set the variable, FileDele to the file in the list and then compare the file extension and the extension from the array created. If the comparison is not equal to 0, which mean they are the same, then we add a count of the extension (RestCount variable) not matched. This will iterate until all the extensions from the array are verified. If the count is equal to the amount of extension matched, then the file is not one of the file types specified and it is removed from the list. Each time the ResCount is set back to zero to reset the process. We then go to the next file in the collection until there is no more. After which the StartUpload subroutine is called.


sub button2_onclick()
    'Establish File Collection
    'The files will upload but will not show up in the progress bar
    Set files = AXFFile.Files
	
	'msgbox("File count: " & files.count)
	Dim ext(2)
	ext(0) = "ini"
	ext(1) = "txt"
	ext(2) = "doc"
	
	Dim FileDele
	for each p in files
		for each x in ext
			FExt = mid(p.filename,instrrev(p.filename,".")+1)
			'msgbox(FExt & " " & x)
			'msgbox(Strcomp(FExt,x))
			FileDele = p.filename
			if Strcomp(FExt,x) <> 0 Then
				
				RestCount = RestCount + 1
				
			end if
			
		next
			'msgbox("Count:" & RestCount)
			If RestCount = 3 Then ' number of extensions to restrict to
				msgbox(FileDele & " will be removed from the file list" & vbcrlf _ 
				& "since it is not the correct file type")
				AXFFile.Remove (p.filename)
				
				
			end if	
		RestCount = 0
	next
	
	Call startupload
	
End Sub

The startUpload subroutine sets the progress window that will be opened through the transfer, and then transfer begins.

sub startupload()
	winstyle = "height=300,width=400,status=no,toolbar=no,menubar=no,location=no"
    	window.open "AXFFileProgress.htm",null,winstyle
	AXFFile.Start()
end sub
</SCRIPT>

You can customize limitation properties, such as MaxBytes. If the limitation fails, the upload will not start. If one file exceeds the limit, no files are uploaded.

Now you can you can restrict file type to uploads and set the max size.