LockedFiles

LockedFiles.java

public class LockedFiles {
    /**
     * Like {@link java.nio.file.Files#write(Path, byte[], OpenOption...)} but with a lock
     */
    public static void write(Path path, byte[] bytes) throws IOException {
        if (bytes == null) {
            return;
        }
        log.debug("Writing {}", path);
        try (FileChannel chan = FileChannel.open(path, TRUNCATE_EXISTING, WRITE, CREATE, DSYNC);
             FileLock lock = chan.lock()) {
            assert lock.isValid();
            ByteBuffer buf = ByteBuffer.wrap(bytes);
            while (0 < buf.remaining()) {
                chan.write(buf);
            }
            chan.force(true);
        } finally {
            log.debug("Wrote {}", path);
        }
    }

    /**
     * Like {@link java.nio.file.Files#readAllBytes} but with a lock
     */
    public static byte[] readAllBytes(Path path) throws IOException {
        log.debug("Reading {}", path);
        try (FileChannel chan = FileChannel.open(path, READ)) {
            FileLock lock = chan.lock(0, Long.MAX_VALUE, true);
            assert lock.isValid();
            long size = chan.size();
            if (size > Integer.MAX_VALUE - 8) {
                throw new OutOfMemoryError("Required array size too large");
            }
            byte[] bytes = new byte[(int) size];
            ByteBuffer buf = ByteBuffer.wrap(bytes);
            //noinspection StatementWithEmptyBody
            while (chan.read(buf) >= 0 && buf.hasRemaining()) {
            }
            return bytes;
        } catch (OverlappingFileLockException e) {
            log.warn(e.toString(), e);
            return new byte[0]; // TODO retry ?
        } finally {
            log.debug("Read {}", path);
        }
    }  
}