package com.mes.ui;

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

public class LockUtil {
    private FileChannel channel;

    private FileLock lock;

    private File file;

    private static LockUtil instance = null;

    /**
     * 获取唯一进程限制的实例
     * @Title: getInstance
     * @return  唯一进程实例
     */
    public static LockUtil getInstance(){
        if(instance == null){
            instance = new LockUtil();
        }
        return instance;
    }

    /**
     * 进程是否正在运行
     * @Title: isAppActive
     * @return  运行与否
     */
    public boolean isAppActive() {
        File file = new File(".lock");
        try {
            channel = new RandomAccessFile(file, "rw").getChannel();
            try {
                lock = channel.tryLock();

            } catch (OverlappingFileLockException e) {
                closeLock();
                return true;
            }
            if (lock == null) {
                closeLock();
                return true;
            }
            Runtime.getRuntime().addShutdownHook(new Thread() {
                public void run() {
                    closeLock();
                    deleteFile();
                }
            });
            return false;
        } catch (Exception e) {
            closeLock();
            return true;
        }
    }

    protected void deleteFile() {
        try {
            file.delete();
        } catch (Exception e) {

        }

    }

    private void closeLock() {
        try {
            lock.release();
        } catch (Exception e) {

        }

        try {
            channel.close();
        } catch (Exception e) {

        }
    }
}