工具类总结(6)-订单生成工具类

/** * 42位的时间前缀+10位的节点标识+12位的sequence避免并发的数字（12位不够用时强制得到新的时间前缀） * <p> * <b>对系统时间的依赖性非常强，需要关闭ntp的时间同步功能，或者当检测到ntp时间调整后，拒绝分配id。 * * @author sumory.wu * @date 2012-2-26 下午6:40:28 */public class IdWorker {//    private final static Logger logger = LoggerFactory.getLogger(IdWorker.class);    private final long workerId;    private final long snsEpoch = 1330328109047L;// 起始标记点，作为基准    private long sequence = 0L;// 0，并发控制    private final long workerIdBits = 10L;// 只允许workid的范围为：0-1023    private final long maxWorkerId = -1L ^ -1L << this.workerIdBits;// 1023,1111111111,10位    private final long sequenceBits = 12L;// sequence值控制在0-4095    private final long workerIdShift = this.sequenceBits;// 12    private final long timestampLeftShift = this.sequenceBits + this.workerIdBits;// 22    private final long sequenceMask = -1L ^ -1L << this.sequenceBits;// 4095,111111111111,12位    private long lastTimestamp = -1L;    public IdWorker(long workerId) {        super();        if (workerId > this.maxWorkerId || workerId < 0) {// workid < 1024[10位：2的10次方]            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", this.maxWorkerId));        }        this.workerId = workerId;    }    public long nextId() throws Exception {        long timestamp = this.timeGen();        if (this.lastTimestamp == timestamp) {// 如果上一个timestamp与新产生的相等，则sequence加一(0-4095循环)，下次再使用时sequence是新值            //System.out.println("lastTimeStamp:" + lastTimestamp);            this.sequence = this.sequence + 1 & this.sequenceMask;            if (this.sequence == 0) {                timestamp = this.tilNextMillis(this.lastTimestamp);// 重新生成timestamp            }        } else {            this.sequence = 0;        }        if (timestamp < this.lastTimestamp) {//            logger.error(String.format("Clock moved backwards.Refusing to generate id for %d milliseconds", (this.lastTimestamp - timestamp)));            throw new Exception(String.format("Clock moved backwards.Refusing to generate id for %d milliseconds", (this.lastTimestamp - timestamp)));        }        this.lastTimestamp = timestamp;        // 生成的timestamp        return timestamp - this.snsEpoch << this.timestampLeftShift | this.workerId << this.workerIdShift | this.sequence;    }    /**     * 保证返回的毫秒数在参数之后     *     * @param lastTimestamp     * @return     */    private long tilNextMillis(long lastTimestamp) {        long timestamp = this.timeGen();        while (timestamp <= lastTimestamp) {            timestamp = this.timeGen();        }        return timestamp;    }    /**     * 获得系统当前毫秒数     *     * @return     */    private long timeGen() {        return System.currentTimeMillis();    }    public static void main(String[] args) throws Exception {        //IdWorker iw1 = new IdWorker(1);        IdWorker iw2 = new IdWorker(2);//        IdWorker iw3 = new IdWorker(3);        long a = iw2.nextId();        for (int i = 0; i < 100; i++)            System.out.println(iw2.nextId());    }}