MyBatis使用雪花ID怎么实现

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一、实现MyBatis ID构建接口

@Slf4j@Componentpublic class CustomIdGenerator implements IdentifierGenerator {    @Override    public Long nextId(Object entity) {        //生成ID        long id = SnowFlakeUtils.nextId();        log.info("生成ID: " + id);        return id;    }}

二、雪花ID生成工具类

@Slf4jpublic class SnowFlakeUtils {    /** 初始偏移时间戳 */    private static final long OFFSET = 1546300800L;    /** 机器id (0~15 保留 16~31作为备份机器) */    private static final long WORKER_ID;    /** 机器id所占位数 (5bit, 支持最大机器数 2^5 = 32)*/    private static final long WORKER_ID_BITS = 5L;    /** 自增序列所占位数 (16bit, 支持最大每秒生成 2^16 = 65536) */    private static final long SEQUENCE_ID_BITS = 16L;    /** 机器id偏移位数 */    private static final long WORKER_SHIFT_BITS = SEQUENCE_ID_BITS;    /** 自增序列偏移位数 */    private static final long OFFSET_SHIFT_BITS = SEQUENCE_ID_BITS + WORKER_ID_BITS;    /** 机器标识最大值 (2^5 / 2 - 1 = 15) */    private static final long WORKER_ID_MAX = ((1 << WORKER_ID_BITS) - 1) >> 1;    /** 备份机器ID开始位置 (2^5 / 2 = 16) */    private static final long BACK_WORKER_ID_BEGIN = (1 << WORKER_ID_BITS) >> 1;    /** 自增序列最大值 (2^16 - 1 = 65535) */    private static final long SEQUENCE_MAX = (1 << SEQUENCE_ID_BITS) - 1;    /** 发生时间回拨时容忍的最大回拨时间 (秒) */    private static final long BACK_TIME_MAX = 1000L;    /** 上次生成ID的时间戳 (秒) */    private static long lastTimestamp = 0L;    /** 当前秒内序列 (2^16)*/    private static long sequence = 0L;    /** 备份机器上次生成ID的时间戳 (秒) */    private static long lastTimestampBak = 0L;    /** 备份机器当前秒内序列 (2^16)*/    private static long sequenceBak = 0L;    static {        // 初始化机器ID        long workerId = getWorkId();        if (workerId < 0 || workerId > WORKER_ID_MAX) {            throw new IllegalArgumentException(String.format("cmallshop.workerId范围: 0 ~ %d 目前: %d", WORKER_ID_MAX, workerId));        }        WORKER_ID = workerId;    }    private static Long getWorkId(){        try {            String hostAddress = Inet4Address.getLocalHost().getHostAddress();            int[] ints = StringUtils.toCodePoints(hostAddress);            int sums = 0;            for(int b : ints){                sums += b;            }            return (long)(sums % WORKER_ID_MAX);        } catch (UnknownHostException e) {            // 如果获取失败，则使用随机数备用            return RandomUtils.nextLong(0,WORKER_ID_MAX-1);        }    }    /** 私有构造函数禁止外部访问 */    private SnowFlakeUtils() {}    /**     * 获取自增序列     * @return long     */    public static long nextId() {        return nextId(SystemClock.now() / 1000);    }    /**     * 主机器自增序列     * @param timestamp 当前Unix时间戳     * @return long     */    private static synchronized long nextId(long timestamp) {        // 时钟回拨检查        if (timestamp < lastTimestamp) {            // 发生时钟回拨            log.warn("时钟回拨, 启用备份机器ID: now: [{}] last: [{}]", timestamp, lastTimestamp);            return nextIdBackup(timestamp);        }        // 开始下一秒        if (timestamp != lastTimestamp) {            lastTimestamp = timestamp;            sequence = 0L;        }        if (0L == (++sequence & SEQUENCE_MAX)) {            // 秒内序列用尽//            log.warn("秒内[{}]序列用尽, 启用备份机器ID序列", timestamp);            sequence--;            return nextIdBackup(timestamp);        }        return ((timestamp - OFFSET) << OFFSET_SHIFT_BITS) | (WORKER_ID << WORKER_SHIFT_BITS) | sequence;    }    /**     * 备份机器自增序列     * @param timestamp timestamp 当前Unix时间戳     * @return long     */    private static long nextIdBackup(long timestamp) {        if (timestamp < lastTimestampBak) {            if (lastTimestampBak - SystemClock.now() / 1000 <= BACK_TIME_MAX) {                timestamp = lastTimestampBak;            } else {                throw new RuntimeException(String.format("时钟回拨: now: [%d] last: [%d]", timestamp, lastTimestampBak));            }        }        if (timestamp != lastTimestampBak) {            lastTimestampBak = timestamp;            sequenceBak = 0L;        }        if (0L == (++sequenceBak & SEQUENCE_MAX)) {            // 秒内序列用尽//            logger.warn("秒内[{}]序列用尽, 备份机器ID借取下一秒序列", timestamp);            return nextIdBackup(timestamp + 1);        }        return ((timestamp - OFFSET) << OFFSET_SHIFT_BITS) | ((WORKER_ID ^ BACK_WORKER_ID_BEGIN) << WORKER_SHIFT_BITS) | sequenceBak;    }    /**     * 并发数     */    private static final int THREAD_NUM = 30000;    private static volatile CountDownLatch countDownLatch = new CountDownLatch(THREAD_NUM);    public static void main(String[] args) {        ConcurrentHashMap map = new ConcurrentHashMap<>(THREAD_NUM);        List list = Collections.synchronizedList(new LinkedList<>());        for (int i = 0; i < THREAD_NUM; i++) {            Thread thread = new Thread(() -> {                // 所有的线程在这里等待                try {                    countDownLatch.await();                    Long id = SnowFlakeUtils.nextId();                    list.add(id);                    map.put(id,1L);                } catch (InterruptedException e) {                    e.printStackTrace();                }            });            thread.start();            // 启动后，倒计时计数器减一，代表有一个线程准备就绪了            countDownLatch.countDown();        }        try{            Thread.sleep(50000);        }catch (Exception e){            e.printStackTrace();        }        System.out.println("listSize:"+list.size());        System.out.println("mapSize:"+map.size());        System.out.println(map.size() == THREAD_NUM);    }}

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