Java 支付交易流水号生成

最新推荐文章于 2024-10-28 10:39:48 发布

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最新推荐文章于 2024-10-28 10:39:48 发布

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CC 4.0 BY-SA版权

文章标签： java 开发语言

本文链接：https://blog.youkuaiyun.com/later_home/article/details/135934938

该文章详细描述了一个名为PayIdGenerator的Java类，它使用静态工厂方法生成具有机器标识、时间戳和序列号的唯一ID，保证了在分布式系统中的时序性和线程安全性。

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public class PayIdGenerator {

    private static PayIdGenerator instance = new PayIdGenerator(0);

    public static PayIdGenerator initDefaultInstance(int machineId) {
        instance = new PayIdGenerator(machineId);
        return instance;
    }

    public static PayIdGenerator getInstance() {
        return instance;
    }

    public static long generateId() {
        return instance.nextId();
    }

    // total bits=53(max 2^53-1：9007199254740992-1)

    // private final static long TIME_BIT = 40; // max: 2318-06-04
    private final static long MACHINE_BIT = 5; // max 31
    private final static long SEQUENCE_BIT = 8; // 256/10ms

    /**
     * mask/max value
     */
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long TIMESTMP_LEFT = MACHINE_BIT + SEQUENCE_BIT;

    private long machineId;
    private long sequence = 0L;
    private long lastStmp = -1L;

    private PayIdGenerator(long machineId) {
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
        }
        this.machineId = machineId;
    }

    /**
     * generate new ID
     *
     * @return
     */
    public synchronized long nextId() {
        long currStmp = getTimestamp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0L) {
                currStmp = getNextTimestamp();
            }
        } else {
            sequence = 0L;
        }

        lastStmp = currStmp;

        return currStmp << TIMESTMP_LEFT //
                | machineId << MACHINE_LEFT //
                | sequence;
    }

    private long getNextTimestamp() {
        long mill = getTimestamp();
        while (mill <= lastStmp) {
            mill = getTimestamp();
        }
        return mill;
    }

    private long getTimestamp() {
        // per 10ms
        return System.currentTimeMillis() / 10;// 10ms
    }
}