File copy coding example - which ...

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Replies: 2 - Pages: 1 - Last Post: 16-Jan-2018 14:12 Last Post By: davidekholm

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Dschuwi

Posts: 483
Registered: 12-Nov-2003

File copy coding example - which approach is better
Posted: 16-Jan-2018 12:50

As a follow-up to a thread in the bugs forum, in general, for cases when it is unknown whether the source file exists, is it good practice to copy a file like this (seized working in jAlbum 15)

try {
  IO.copyFile(f, r);
}
 catch(IOException e) {}

or better to perform a file existence check instead

if (f.exists()) {
  IO.copyFile(f, r);
}

jGromit

Posts: 7,647
Registered: 31-Jan-2006

Re: File copy coding example - which approach is better
Posted: 16-Jan-2018 14:00

in response to: Dschuwi

You might still need an error trap, because the file copy might fail for other reasons.

The source file might exist, but might be locked. This happens in Windows with media files like MP3 and MP4 if you've opened the file in your browser, and the browser is still open, even if you've closed the file. You actually have to close the browser to avoid the error.

Or the destination directory might not exist, or be "read-only."

davidekholm

Posts: 3,658
Registered: 18-Oct-2002

Re: File copy coding example - which approach is better
Posted: 16-Jan-2018 14:12

in response to: jGromit

It's never wrong to perform an existence check. v15.1.5 is now fixed to properly throw a FileNotFoundException if the source file is missing before attempting to delete the target file. (The target file deletion was added when introducing hard links. Without it, there is a risk that the source file gets truncated to zero bytes).

Also remember to put the catch clause after any other code that relies on that successful copy.

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