Wonders of Code - Simplicity vs. Robustness In Lock File Handling (http://wp.me/p3ui6n-1k) - the robust re-design

RobustSingletonBatchJob.java

public class RobustSingletonBatchJob {
    
    // Note: We could use File.deleteOnExit() but the docs says it is not 100% reliable and recommends to
    // use java.nio.channels.FileLock; however this code works well enough for us
    static synchronized boolean getLock() {
        File file = new File(LOCK_DIRECTORY, StaticConfiguration.getGroupPrefix());
        try {
            // Will try to create path to lockfile if it does not exist.
            file.getParentFile().mkdirs(); // #1 Create the lock dir if it doesn't exist
            if (file.createNewFile()) {
                return true;
            } else {
                log.info("Lock file " + file.getAbsolutePath() + " already exists."); // #2 Helpful error msg w/ path
                return false;
            }
        } catch (IOException e) {
            throw new RuntimeException("Failed to create lock file " + file.getAbsolutePath()
               + " due to " + e + ". Fix the problem and retry."
               , e); // #3 Helpful error message with context (file path)
        }
    }

    private synchronized static void releaseLock() {
        File file = new File(LOCK_DIRECTORY, StaticConfiguration.getGroupPrefix());
        file.delete();
    }
    
    public static void main(String[] args) throws Exception {
        boolean releaseLockUponCompletion = true;
        try {
            ...
            if (! getLock() {
                releaseLockUponCompletion = false;
                log.error("Lock file is present, exiting."); // Lock path already logged
                throw new RuntimeException("Lock file is present"); // throwing is nicer than System.exit/return
            }
            ... // do the job (may throw exceptions)
        } finally {
            if (releaseLockUponCompletion) {
                releaseLock(); // #4 Always release the lock, even upon exceptions
            }
        }
}