分散式ID-雪花演算法ID工具類

package entity;import java.lang.management.ManagementFactory;import java.net.InetAddress;import java.net.NetworkInterface;/** * <p>名稱：IdWorker.java</p> * <p>描述：分散式自增長ID</p> * <pre> *     Twitter的 Snowflake　JAVA實現方案 * </pre> * 核心程式碼為其IdWorker這個類實現，其原理結構如下，我分別用一個0表示一位，用—分割開部分的作用： * 1||0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000 * 在上面的字串中，第一位為未使用（實際上也可作為long的符號位），接下來的41位為毫秒級時間， * 然後5位datacenter標識位，5位機器ID（並不算識別符號，實際是為執行緒標識）， * 然後12位該毫秒內的當前毫秒內的計數，加起來剛好64位，為一個Long型。 * 這樣的好處是，整體上按照時間自增排序，並且整個分散式系統內不會產生ID碰撞（由datacenter和機器ID作區分）， * 並且效率較高，經測試，snowflake每秒能夠產生26萬ID左右，完全滿足需要。 * <p> * 64位ID (42(毫秒)+5(機器ID)+5(業務編碼)+12(重複累加)) * * @author Polim */public class IdWorker {    // 時間起始標記點，作為基準，一般取系統的最近時間（一旦確定不能變動）    private final static long twepoch = 1288834974657L;    // 機器標識位數    private final static long workerIdBits = 5L;    // 資料中心標識位數    private final static long datacenterIdBits = 5L;    // 機器ID最大值    private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);    // 資料中心ID最大值    private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);    // 毫秒內自增位    private final static long sequenceBits = 12L;    // 機器ID偏左移12位    private final static long workerIdShift = sequenceBits;    // 資料中心ID左移17位    private final static long datacenterIdShift = sequenceBits + workerIdBits;    // 時間毫秒左移22位    private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;    private final static long sequenceMask = -1L ^ (-1L << sequenceBits);    /* 上次生產id時間戳 */    private static long lastTimestamp = -1L;    // 0，併發控制    private long sequence = 0L;    private final long workerId;    // 資料標識id部分    private final long datacenterId;    public IdWorker(){        this.datacenterId = getDatacenterId(maxDatacenterId);        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);    }    /**     * @param workerId     *            工作機器ID     * @param datacenterId     *            序列號     */    public IdWorker(long workerId, long datacenterId) {        if (workerId > maxWorkerId || workerId < 0) {            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));        }        if (datacenterId > maxDatacenterId || datacenterId < 0) {            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));        }        this.workerId = workerId;        this.datacenterId = datacenterId;    }    /**     * 獲取下一個ID     *     * @return     */    public synchronized long nextId() {        long timestamp = timeGen();        if (timestamp < lastTimestamp) {            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));        }        if (lastTimestamp == timestamp) {            // 當前毫秒內，則+1            sequence = (sequence + 1) & sequenceMask;            if (sequence == 0) {                // 當前毫秒內計數滿了，則等待下一秒                timestamp = tilNextMillis(lastTimestamp);            }        } else {            sequence = 0L;        }        lastTimestamp = timestamp;        // ID偏移組合生成最終的ID，並返回ID        long nextId = ((timestamp - twepoch) << timestampLeftShift)                | (datacenterId << datacenterIdShift)                | (workerId << workerIdShift) | sequence;        return nextId;    }    private long tilNextMillis(final long lastTimestamp) {        long timestamp = this.timeGen();        while (timestamp <= lastTimestamp) {            timestamp = this.timeGen();        }        return timestamp;    }    private long timeGen() {        return System.currentTimeMillis();    }    /**     * <p>     * 獲取 maxWorkerId     * </p>     */    protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {        StringBuffer mpid = new StringBuffer();        mpid.append(datacenterId);        String name = ManagementFactory.getRuntimeMXBean().getName();        if (!name.isEmpty()) {            /*             * GET jvmPid             */            mpid.append(name.split("@")[0]);        }        /*         * MAC + PID 的 hashcode 獲取16個低位         */        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);    }    /**     * <p>     * 資料標識id部分     * </p>     */    protected static long getDatacenterId(long maxDatacenterId) {        long id = 0L;        try {            InetAddress ip = InetAddress.getLocalHost();            NetworkInterface network = NetworkInterface.getByInetAddress(ip);            if (network == null) {                id = 1L;            } else {                byte[] mac = network.getHardwareAddress();                id = ((0x000000FF & (long) mac[mac.length - 1])                        | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;                id = id % (maxDatacenterId + 1);            }        } catch (Exception e) {            System.out.println(" getDatacenterId: " + e.getMessage());        }        return id;    }    public static void main(String[] args) {        IdWorker idWorker = new IdWorker(0,0);		        for (int i = 0; i <10000; i++) {            long nextId=idWorker.nextId();			System.out.println(nextId);        }    }}