Question

When I start my application I create a temp folder:

  public static File createTempDir(String name) throws IOException {
    File tempDir = File.createTempFile(name, "");
    if (!(tempDir.delete())) {
      throw new IOException("could not delete" + tempDir.getAbsolutePath());
    }

    if (!(tempDir.mkdir())) {
      throw new IOException("could not create" + tempDir.getAbsolutePath());
    }
    tempDir.deleteOnExit();
    return tempDir;
  }

During a session a user might load a file. As a result the old temp dir is deleted and a new is created based on the ID of the file loaded.

During load where the old temp dir is deleted I sometimes get a:

java.io.IOException: Unable to delete file:

Here is how the old temp folder is deleted:

  public void cleanup(String tmpPath) {
    File tmpFolder = new File(tmpPath);
    if (tmpFolder != null && tmpFolder.isDirectory()) {
      try {
        FileUtils.deleteDirectory(file);
      } catch (IOException e) {
            e.printStackTrace();
      }
    } 
  }

where FileUtils is: org.apache.commons.io.FileUtils. Typically the content of the temp folder is:

mytempfolder_uuid
|-> mysubfolder
|-> myImage.jpg

And the error is:

java.io.IOException: Unable to delete file: C:\Users\xxx\AppData\Local\Temp\mytempfolder_uuid\mysubfolder\myImage.jpg

I have tried to debug the application and before the delete operation is executed verified that the above image is actually located in the specified folder.

The nasty thing is that it only happens sometimes. I have made sure not to have the folder/files in the temp folder open in any other applications. Any ideas/suggestions?

Answer 1

I’d suggest you use the Guava library. It has a method Files.createTempDir() that does exactly what you seem to need:

Atomically creates a new directory somewhere beneath the system’s
temporary directory (as defined by the java.io.tmpdir system
property), and returns its name. Use this method instead of
File.createTempFile(String, String) when you wish to create a
directory, not a regular file. A common pitfall is to call
createTempFile, delete the file and create a directory in its place,
but this leads a race condition which can be exploited to create
security vulnerabilities, especially when executable files are to be
written into the directory. This method assumes that the temporary
volume is writable, has free inodes and free blocks, and that it will
not be called thousands of times per second.