如何自定义Mybatis-Plus分布式ID生成器(解决ID长度超过JavaScript整数安全范围问题)

缩短雪花算法后空间划分（可根据实际需求调整）：
1. 高位 32bit 作为秒级时间戳, 时间戳减去固定值(2024 年时间戳)
2. 5bit 作为机器标识, 最高可部署 32 台机器
3. 最后 16bit 作为自增序列, 单节点最高每秒 2^16 = 65536 个 ID

import com.baomidou.mybatisplus.core.incrementer.IdentifierGenerator;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
/**
 * 符合 JavaScript 整数安全范围的自定义ID生成器
 *
 * @author PANDA
 */
@Slf4j
@Component
public class JsSafeIdGenerator implements IdentifierGenerator {
    /** 初始偏移时间戳 2024-01-01 */
    private static final long OFFSET = 1704067200L;
    /** 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 = 1L;
    /** 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 可配置文件获取
        long workerId = 1;
        if (workerId < 0 || workerId > WORKER_ID_MAX) {
            throw new IllegalArgumentException(String.format("worker-id [%d] 越界, 有效范围: 0 ~ %d ", workerId, WORKER_ID_MAX));
        }
        WORKER_ID = workerId;
    }
    @Override
    public synchronized Number nextId(Object entity) {
        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) {
        if (timestamp < lastTimestamp) {
            log.warn("时钟回拨, 启用备份机器ID: now: [{}] last: [{}]", timestamp, lastTimestamp);
            return nextIdBackup(timestamp);
        }
        if (timestamp != lastTimestamp) {
            lastTimestamp = timestamp;
            sequence = 0L;
        }
        if (0L == (++sequence & SEQUENCE_MAX)) {
            sequence--;
            return nextIdBackup(Math.max(timestamp, lastTimestampBak));
        }
        return ((timestamp - OFFSET) << OFFSET_SHIFT_BITS) | (WORKER_ID << WORKER_SHIFT_BITS) | sequence;
    }
    /**
     * 备份机器自增序列
     * @param 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)) {
            return nextIdBackup(timestamp + 1);
        }
        return ((timestamp - OFFSET) << OFFSET_SHIFT_BITS) | ((WORKER_ID ^ BACK_WORKER_ID_BEGIN) << WORKER_SHIFT_BITS) | sequenceBak;
    }
}

import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
 * 缓存时间戳解决System.currentTimeMillis()高并发下性能问题
 *
 * @author PANDA
 **/
public class SystemClock {
    private final long period;
    private final AtomicLong now;
    private SystemClock(long period) {
        this.period = period;
        this.now = new AtomicLong(System.currentTimeMillis());
        scheduleClockUpdating();
    }
    /**
     * 尝试下枚举单例法
     */
    private enum SystemClockEnum {
        SYSTEM_CLOCK;
        private SystemClock systemClock;
        SystemClockEnum() {
            systemClock = new SystemClock(1);
        }
        public SystemClock getInstance() {
            return systemClock;
        }
    }
    /**
     * 获取单例对象
     * @return com.cmallshop.module.core.commons.util.sequence.SystemClock
     */
    private static SystemClock getInstance() {
        return SystemClockEnum.SYSTEM_CLOCK.getInstance();
    }
    /**
     * 获取当前毫秒时间戳
     * @return long
     */
    public static long now() {
        return getInstance().now.get();
    }
    /**
     * 起一个线程定时刷新时间戳
     */
    private void scheduleClockUpdating() {
        ScheduledThreadPoolExecutor scheduler = new ScheduledThreadPoolExecutor(1, runnable -> {
            Thread thread = new Thread(runnable, "System Clock");
            thread.setDaemon(true);
            return thread;
        });
        scheduler.scheduleAtFixedRate(() -> now.set(System.currentTimeMillis()), period, period, TimeUnit.MILLISECONDS);
    }
}

import com.baomidou.mybatisplus.core.config.GlobalConfig;
import lombok.RequiredArgsConstructor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@RequiredArgsConstructor
public class MybatisPlusConfiguration {
    @Bean
    public GlobalConfig globalConfig() {
        GlobalConfig globalConfig = new GlobalConfig();
        globalConfig.setIdentifierGenerator(new JsSafeIdGenerator());
        return globalConfig;
    }
}

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Base implements Serializable {
    @TableId(type = IdType.ASSIGN_ID)
    private Long id;
}