Copying a file using FileUtils.copyFile

Question

I am trying to copy files using file utils copy file method. I am running in to some issues where an exception is some times thrown

java.io.IOException: Failed to copy full contents from 'path.xml' to localfile.xml

I have googled and seen in the code that this exception is thrown when the target file length is different to the destination file length, The exception only occures some times - this could be due to the fact that the file i am trying to copy is consistantly updating so i might catch it mid update(just an xml file with values changing)

If i wrap the call in a if(target.canRead()) but this seems to make little difference.

Can anyone help?

*update:*I cannot lock the file as it is being written to via a third party vendor, this would cause all sorts of problems.

I suggest to use [Google guava API](https://code.google.com/p/guava-libraries/) [Files Class](http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/io/Files.html), — ajduke, Apr 04 '13 at 07:53
because it has the Files.copy(src,dest) method and its Google Guava library and i am using it in all Java projets , did not found the issues so far. — ajduke, Apr 05 '13 at 11:11
The real question here is why are you copying a file that is still being written to? — user207421, Oct 17 '17 at 22:52

score 1 · Accepted Answer · edited May 23 '17 at 12:29

I am not sure about how the architecture is implemented in your project, but you should have a locking mechanism on the file.

When some one is writing to the file it should lock it. And you should not be copying from it while its being written, ie it is locked.

FileInputStream in = new FileInputStream(file);
try {
    java.nio.channels.FileLock lock = in.getChannel().lock();
    try {
        Reader reader = new InputStreamReader(in, charset);
        ...
    } finally {
        lock.release();
    }
} finally {
    in.close();
}

See this question here on how to lock a file in java.

UPDATE

You are then left with no option but to implement copy method yourself or use a library that does not have a similar check.

You can see the code of FileUtils

It will give error if file changes during copy.

        if (srcFile.length() != destFile.length()) {
            throw new IOException("Failed to copy full contents from '" +
                    srcFile + "' to '" + destFile + "'");
        }

score 1 · Answer 2 · answered Dec 11 '14 at 12:45

I have the same problem (with large files) resolved using Files in Java 7 :

File srcFile = ...
File destFile = ...
File directory = ...
if (!Files.exists(directory.toPath())) {
    // use forceMkdir to create parent directory
    FileUtils.forceMkdir(directory);
}
Files.copy(srcFile.toPath(), new FileOutputStream(destFile));

score 0 · Answer 3 · edited May 23 '17 at 11:43

0

Well as you said the file might get updated during your copy process, so you should be required to get a file lock on the file you want to copy.

I suggest reading this question to get some detailed information of how to use a FileLock.

edited May 23 '17 at 11:43

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answered Apr 04 '13 at 07:50

Michael Rose

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Copying a file using FileUtils.copyFile

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