大家好，最近在用java做后台程序。这个后台程序是系统无关的，可以运行在Windows，也可以运行在Linux。这个java程序，被我用可运行的jar进行执行，要求每个执行jar只能被启动一个进程。为了达到这个目的，我找了资料，有的朋友说启动一个端口，每次启动的时候都做检查，发现端口被占，则说明已经存在该jar的进程在系统中。但是我觉得一个程序占用一个端口，浪费资源。所以继续查找资料，发现用nio的文件锁可以实现。我写了代码，在windows上面运行正常。但是在Linux上面（red hat）上面却运行失败，依然启动了N个进程，而我期望的就是一个经常，在启动更多的进程时会有警告信息。请教高手，该如何处理？下面是我的代码。请指教。
- Java code
/** * */import java.io.File;import java.io.FileWriter;import java.io.RandomAccessFile;import java.nio.channels.FileChannel;import java.nio.channels.FileLock;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;import org.apache.log4j.Logger;public class Test { private static Logger logger = Logger.getLogger(Test.class); /** * @param args */ public static void main(String[] args) { lockSingletonProgramFile(Test.class.getName()); ExecutorService exec = Executors.newSingleThreadExecutor(); exec.execute(new Runnable(){ @Override public void run() { while(true){ try { TimeUnit.SECONDS.sleep(30); } catch (InterruptedException e) { e.printStackTrace(); } } }}); exec.shutdown(); } /** * method destination : privent starting more than one program process in * system processes * * @param programName */ private static void lockSingletonProgramFile(String programName) { final String startFailureMessage = "Error:start " + programName + " application"; String lockFile = System.getProperty("lockFile"); logger.info("start " + programName + " application with [lockFile] : " + lockFile); if (null == lockFile) { String userDir = System.getProperty("user.dir"); File userDirFile = new File(userDir); lockFile = userDirFile.getParent() + File.separator + programName + ".lock"; logger.warn("does not provide lockFile, it will use default lockFile which is [" + lockFile + "]"); } RandomAccessFile raf = null; FileChannel fileChannel = null; FileLock flock = null; FileWriter writer = null; try { File file = new File(lockFile); if (!file.exists()) { String parent = file.getParent(); File folder = new File(parent); if (!folder.exists() || !folder.isDirectory()) { if (!folder.mkdirs()) { logger.error(startFailureMessage + " failure: create lock file folder failure:" + parent); System.exit(-1); } } if (!file.createNewFile()) { logger.error(startFailureMessage + " failure: create lock file failure:" + lockFile); System.exit(-1); } } writer = new FileWriter(file); writer.write(programName); /** * Here,we force flush data into lock file. If there already has a * process in system processes, it will catch Exception. */ writer.flush(); writer.close(); raf = new RandomAccessFile(file, "rw"); fileChannel = raf.getChannel(); flock = fileChannel.tryLock();// start to try locking lock file /** * <pre> * Note: * Here, at first time, you cann't release or close these resources. * If you do it, you will find that it cann't prevent more than one program process * running in system processes. * </pre> */ } catch (Exception e) { logger.error(startFailureMessage + " failure: lock file is [" + lockFile + "]:" + e.getMessage(), e); try { /** * <pre> * Note: * If you start program process failure, * you need to try releasing and closing these resources. * </pre> */ if (null != writer) { writer.close(); } if (null != flock) { flock.release(); } if (null != fileChannel) { fileChannel.close(); } if (null != raf) { raf.close(); } } catch (Exception ex) { logger.error( "Error: close resource failure:" + ex.getMessage(), ex); } logger.error("There is a " + programName + " application process in system processes. Now exit starting!"); System.exit(-1); } }}