FileSystemLock

gistfile1.java

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileLock;
import java.nio.channels.OverlappingFileLockException;

import static com.google.common.base.Preconditions.checkNotNull;

public class FileSystemLock {
    private final File lockFile;
    private RandomAccessFile writer;
    private FileLock writeLock;
    private boolean closed;

    public FileSystemLock(File lockFile) {
        this.lockFile = checkNotNull(lockFile);
    }

    public boolean tryLock() {
        try {
            writer = new RandomAccessFile(lockFile, "rw");
            writeLock = writer.getChannel().tryLock(Long.MAX_VALUE - 1, 1, false);
        } catch (OverlappingFileLockException e) {
            // Already locked by this JVM
            return false;
        } catch (Exception e) {
            // TODO log e
            return false;
        }

        if (writeLock == null) {
            release();
            return false;
        } else {
            return true;
        }
    }

    public void release() {
        if (!closed) {
            closed = true;

            if (writeLock != null) {
                try {
                    writeLock.release();
                } catch (IOException e) {
                    // TODO log e
                }
            }

            if (writer != null) {
                try {
                    writer.close();
                } catch (IOException e) {
                    // TODO log e
                }
            }
        }
    }
}