What are possible reasons for java.io.IOException: “The filename, directory name, or volume label syntax is incorrect”

Question

I am trying to copy a file using the following code:

File targetFile = new File(targetPath + File.separator + filename);
...
targetFile.createNewFile();
file         


        

Answer 1

Try adding some logging to see exactly what is the name and path the file is trying to create, to ensure that the parent is well a directory.

In addition, you can also take a look at Channels instead of using a loop. ;-)

Answer 2

Maybe the problem is that it is copying the file over the network, to a shared drive? I think java can have problems when writing files using NFS when the path is something like \mypc\myshared folder.

What is the path where this problem happens?

Answer 3

Maybe the file already exists. It could be the case if your timestamp resolution is not good enough. As it is an IOException that you are getting, it might not be a permission issue (in which case you would get a SecurityException).

I would first check for file existence before trying to create the file and try to log what's happening.

Look at public boolean createNewFile() for more information on the method you are using.

Answer 4

As I was not able to reproduce the error on my own machine or get hands on the machine of the user where the code failed I waited until now to declare an accepted answer. I changed the code to the following:

File parentFolder = new File(targetPath);
... do some checks on parentFolder here ...
File targetFile = new File(parentFolder, filename);
targetFile.createNewFile();
fileInputStream = new FileInputStream(fileToCopy);
fileOutputStream = new FileOutputStream(targetFile);
byte[] buffer = new byte[64*1024];
int i = 0;
while((i = fileInputStream.read(buffer)) != -1) {
    fileOutputStream.write(buffer, 0, i);
}

After that it worked for the user reporting the problem.

So it seems Alexanders answer did the trick - although I actually use a slightly different constructor than he gave, but along the same lines.

I yet have to talk that user into helping me verifying that the code change fixed the error (instead of him doing something differently) by running the old version again and checking if it still fails.

btw. logging was in place and the logged path seemed ok - sorry for not mentioning that. I took that for granted and found it unnecessarily complicated the code in the question.

Thanks for the helpful answers.

Answer 5

You say "for some users" - so it works for others? What is the difference here, are the users running different instances on different machines, or is this a server that services concurrent users?

If the latter, I'd say it is a concurrency bug somehow - two threads check try to create the file with WinNTFileSystem.createFileExclusively(Native Method) simultaniously.

Neither createNewFile or createFileExclusively are synchronized when I look at the OpenJDK source, so you may have to synchronize this block yourself.

Answer 6

This can occur when filename has timestamp with colons, eg. myfile_HH:mm:ss.csv Removing colons fixed the issue.