validate a file extension

[Mike Phillip]

Hi, I doing a server that upload and saves files, it's working fine.

But, I need to let only some extension (like txt and jpg), I'm using the file extension, if it's different I refuse, but a user can rename the file extension before the upload and bypass it.

I found a software called JMimeMagic, it's good, but works with most of thw files, but some time doesn't validate some real txt.

works like this:

// snippet for JMimeMagic lib
//     <a href="http://sourceforge.net/projects/jmimemagic/" target="_blank" rel="nofollow">http://sourceforge.net/projects/jmimemagic/</a>
 
Magic parser = new Magic() ;
// getMagicMatch accepts Files or byte[], 
// which is nice if you want to test streams
MagicMatch match = parser.getMagicMatch(new File("gumby.gif"));
System.out.println(match.getMimeType()) ;    

any good solution/software for that?

[Ulf Dittmer]

I'm not sure how JMimeMagic works, but if it's image formats you need to deal with, have a look at the ImageInfo class. It identifies a number of image formats based on the contents, not on the name or MIME type.

[Mike Phillip]

thanks for reply.

Well, it's most image and text. With images the JMimemagic is great, the problem is with txt, some times it fails.

[Stefan Wagner]

How does it fail?
Accept a file as txt which isn't?
Deny a file, which is a txt-file?

How is it identified, if not as txt?