java-insagent-pc/src/main/java/com/ydtech/utils/SnowflakeIdVariant.java

package com.ydtech.utils;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.TimeUnit;

/**
 * Twitter_Snowflake<br>
 * SnowFlake改进符合业务的结构如下(每部分用-分开):<br>
 * bizCode(业务代码) + 201805051212(日期) + 4096(毫秒内随机数)<br>
 */

/**** 
 * @ClassName: SnowflakeIdWorker
 * @Description:
 * @author ccc520
 * @date 2018年6月5日 上午8:44:27  
 * @modificationHistory===============逻辑或功能性重大变更记录
 * @modify by user：  (修改人)
 * @modify by reason：  (修改原因) 
 */
public class SnowflakeIdVariant {

    // ==============================Fields===========================================
    /**
     * 序列在id中占的位数
     */
    private final long sequenceBits = 12L;
    /**
     * 生成序列的掩码，这里为4095 (0b111111111111=0xfff=4095)
     */
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);
    /**
     * 毫秒内序列(0~4095)
     */
    private long sequence = 0L;
    /**
     * 上次生成ID的时间截
     */
    private long lastTimestamp = -1L;

    private static ThreadLocal<SimpleDateFormat> threadLocal = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue() {
            return new SimpleDateFormat("yyyyMMddhhmmssSSS");
        }
    };

    //==============================Constructors=====================================  

    /**
     * 构造函数
     */
    public SnowflakeIdVariant() {
    }

    // ==============================Methods==========================================  

    /**
     * 获得下一个ID (该方法是线程安全的)
     *
     * @return SnowflakeId
     */
    public synchronized String nextId(String machineId, String bizCode) {
        long timestamp = timeGen();
        //如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常  
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(
                    String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }
        //如果是同一时间生成的，则进行毫秒内序列  
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            //毫秒内序列溢出  
            if (sequence == 0) {
                //阻塞到下一个毫秒,获得新的时间戳  
                timestamp = tilNextMillis(lastTimestamp);
            }
        }
        //时间戳改变，毫秒内序列重置  
        else {
            sequence = 0L;
        }
        //上次生成ID的时间截  
        lastTimestamp = timestamp;
        //移位并通过或运算拼到一起组成64位的ID

//        return bizCode + machineId + (threadLocal.get().format(new Date(timestamp))) + String.format("%05d",sequence);
        String precision = "5"; //几位序列号
        String format = "%0" + precision + "d";
        return bizCode + machineId + (threadLocal.get().format(new Date(timestamp))) + String.format(format, sequence);
    }

    /**
     * 阻塞到下一个毫秒，直到获得新的时间戳
     *
     * @param lastTimestamp 上次生成ID的时间截
     * @return 当前时间戳
     */
    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    /**
     * 返回以毫秒为单位的当前时间
     *
     * @return 当前时间(毫秒)
     */
    protected long timeGen() {
        return System.currentTimeMillis();
    }
    //==============================Test=============================================  

    /**
     * 测试
     */
//    public static void main(String[] args) throws InterruptedException {
//        System.out.println(SysConstants.MAC_ADDRESS);
//        String machineId = SysConstants.MAC_ADDRESS.replaceAll("-", "").substring(0,3);
//        SnowflakeIdVariant idWorker = new SnowflakeIdVariant();
//        long time1 = System.currentTimeMillis();
//        for (int i = 0; i < 100000; i++) {
////            String id = idWorker.nextId("001","ORC");
//            String id = idWorker.nextId(machineId,"ORC");
//            //Thread.sleep(1);
//            System.out.println(id);
//        }
//        System.out.println(System.currentTimeMillis()-time1);
//    }

    //	////////////  test  ////////////
    public static void main(String[] args) throws Exception {
        final Set<String> set = new HashSet();

        SnowflakeIdVariant idWorker = new SnowflakeIdVariant();
        final CyclicBarrier cdl = new CyclicBarrier(100);

        for (int i = 0; i < 10000; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        cdl.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } catch (BrokenBarrierException e) {
                        e.printStackTrace();
                    }

                    // id
                    String id = idWorker.nextId("001", "ORC");
                    if (set.contains(id)) {
                        System.out.println(id + " exists");
                    }
                    set.add(id);
                    System.out.println(id);

                    // id2
                    String id2 = idWorker.nextId("001", "ORC");
                    if (set.contains(id2)) {
                        System.out.println(id2 + " exists");
                    }
                    set.add(id2);
                    System.out.println(id2);
                }
            }).start();
        }
        try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}