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package goja.core.kits.lang;

import com.google.common.collect.Lists;

import goja.core.StringPool;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.lang.management.ManagementFactory;
import java.nio.channels.FileLock;
import java.util.List;

/**
 *  . 
 *
 * @author sagyf yang
 * @version 1.0 2014-01-04 14:02
 * @since JDK 1.6
 */
public class JVMKit {
    private static final Logger logger = LoggerFactory.getLogger(JVMKit.class);

    static List jvmFile = Lists.newArrayList();

//    static List jvmSockets = Lists.newArrayList();

    /**
     * 得到当时进程PID,如果没有得到，返回-1
     *
     * @return 进程PID
     */
    public static int getPid() {
        String name = ManagementFactory.getRuntimeMXBean().getName();
        int indexOf = name.indexOf(StringPool.AT);
        if (indexOf > 0) {
            return Integer.parseInt(name.substring(0, indexOf));
        } else {
            return -1;
        }
    }

    /**
     * 锁定一个临时文件，以便实现一台服务器只能启动一个进程
     *
     * @param lockName 类名称
     */
    public static void lockFileForOnlyProcess(Class lockName) {
        lockFileForOnlyProcess(lockName.getName());
    }

    /**
     * 锁定一个临时文件，以便实现一台服务器只能启动一个进程
     *
     * @param lockName 临时文件名称,不要带目录名称
     */
    public static void lockFileForOnlyProcess(String lockName) {
        File file = new File(System.getProperty("java.io.tmpdir"), lockName + ".lock");
        try {
            FileOutputStream output = new FileOutputStream(file);
            FileLock fileLock = output.getChannel().tryLock();
            if (fileLock == null) {
                logger.warn("文件:'" + file + "'已经被lock,进程已经启动,系统将退出");
                System.exit(1);
            }

            PrintStream printStream = new PrintStream(output);
            printStream.println(getPid());
            printStream.flush();

            jvmFile.add(fileLock);
            logger.info("成功lock文件:'" + file + "',用以避免程序被多次启动,pid:" + getPid());
        } catch (IOException e) {
            logger.warn("获得文件lock时异常:'" + file + "',系统退出", e);
            System.exit(2);
        }
    }
}