JAVA实现雪花算法生成唯一订单号工具类的方法

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import lombok.SneakyThrows;import lombok.extern.slf4j.Slf4j;import java.util.Calendar;/** * Default distributed primary key generator. *  * 
 * Use snowflake algorithm. Length is 64 bit. * 
 *  * 
 * 1bit   sign bit. * 41bits timestamp offset from 2016.11.01(ShardingSphere distributed primary key published data) to now. * 10bits worker process id. * 12bits auto increment offset in one mills * 
 *  * 
 * Call @{@code DefaultKeyGenerator.setWorkerId} to set worker id, default value is 0. * 
 *  * 
 * Call @{@code DefaultKeyGenerator.setMaxTolerateTimeDifferenceMilliseconds} to set max tolerate time difference milliseconds, default value is 0. * 
 *  * @author gaohongtao */@Slf4jpublic final class SnowflakeKeyGenerator {        public static final long EPOCH;        private static final long SEQUENCE_BITS = 12L;        private static final long WORKER_ID_BITS = 10L;        private static final long SEQUENCE_MASK = (1 << SEQUENCE_BITS) - 1;        private static final long WORKER_ID_LEFT_SHIFT_BITS = SEQUENCE_BITS;        private static final long TIMESTAMP_LEFT_SHIFT_BITS = WORKER_ID_LEFT_SHIFT_BITS + WORKER_ID_BITS;        private static final long WORKER_ID_MAX_VALUE = 1L << WORKER_ID_BITS;        private static long workerId;    private static int maxTolerateTimeDifferenceMilliseconds = 10;    static {        Calendar calendar = Calendar.getInstance();        calendar.set(2016, Calendar.NOVEMBER, 1);        calendar.set(Calendar.HOUR_OF_DAY, 0);        calendar.set(Calendar.MINUTE, 0);        calendar.set(Calendar.SECOND, 0);        calendar.set(Calendar.MILLISECOND, 0);        EPOCH = calendar.getTimeInMillis();    }        private byte sequenceOffset;        private long sequence;        private long lastMilliseconds;        /**     * Set work process id.     *      * @param workerId work process id     */    public static void setWorkerId(final long workerId) {        if (workerId < 0L || workerId >= WORKER_ID_MAX_VALUE) {            throw new IllegalArgumentException();        }        SnowflakeKeyGenerator.workerId = workerId;    }        /**     * Set max tolerate time difference milliseconds.     *     * @param maxTolerateTimeDifferenceMilliseconds max tolerate time difference milliseconds     */    public static void setMaxTolerateTimeDifferenceMilliseconds(final int maxTolerateTimeDifferenceMilliseconds) {        SnowflakeKeyGenerator.maxTolerateTimeDifferenceMilliseconds = maxTolerateTimeDifferenceMilliseconds;    }        /**     * Generate key.     *      * @return key type is @{@link Long}.     */    public synchronized Long generateKey() {        long currentMilliseconds = System.currentTimeMillis();        if (waitTolerateTimeDifferenceIfNeed(currentMilliseconds)) {            currentMilliseconds = System.currentTimeMillis();        }        if (lastMilliseconds == currentMilliseconds) {            if (0L == (sequence = (sequence + 1) & SEQUENCE_MASK)) {                currentMilliseconds = waitUntilNextTime(currentMilliseconds);            }        } else {            vibrateSequenceOffset();            sequence = sequenceOffset;        }        lastMilliseconds = currentMilliseconds;        return ((currentMilliseconds - EPOCH) << TIMESTAMP_LEFT_SHIFT_BITS) | (workerId << WORKER_ID_LEFT_SHIFT_BITS) | sequence;    }        @SneakyThrows    private boolean waitTolerateTimeDifferenceIfNeed(final long currentMilliseconds) {        if (lastMilliseconds <= currentMilliseconds) {            return false;        }        long timeDifferenceMilliseconds = lastMilliseconds - currentMilliseconds;        if (timeDifferenceMilliseconds >= maxTolerateTimeDifferenceMilliseconds) {            log.error(String.format("Clock is moving backwards, last time is %d milliseconds, current time is %d milliseconds", lastMilliseconds, currentMilliseconds));            //throw new IllegalStateException(String.format("Clock is moving backwards, last time is %d milliseconds, current time is %d milliseconds", lastMilliseconds, currentMilliseconds));        }        Thread.sleep(timeDifferenceMilliseconds);        return true;    }        private long waitUntilNextTime(final long lastTime) {        long result = System.currentTimeMillis();        while (result <= lastTime) {            result = System.currentTimeMillis();        }        return result;    }        private void vibrateSequenceOffset() {        sequenceOffset = (byte) (~sequenceOffset & 1);    }}

spring boot配置文件：

keyGenerator:  snowflake:    workerId: 20 #进程ID，每个实例都要设置不同的值，范围：0-1023    maxTolerateTime: 1500 #最大容忍时钟回退时间，单位：毫秒

如果mybati使用了plugins插件，可以继承进来

import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;import org.mybatis.spring.annotation.MapperScan;import org.springframework.beans.factory.annotation.Value;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.transaction.annotation.EnableTransactionManagement;@EnableTransactionManagement@Configuration@MapperScan({"com.csair.module.*.mybatis.mapper"})public class MybatisPlusConfiguration {    @Bean    public PaginationInterceptor paginationInterceptor() {        return new PaginationInterceptor();    }        @Bean    public SnowflakeKeyGenerator getSnowflakeKeyGenerator(@Value("${keyGenerator.snowflake.workerId}")Integer workerId,                                                          @Value("${keyGenerator.snowflake.maxTolerateTime}")Integer maxTolerateTime){        SnowflakeKeyGenerator.setWorkerId(workerId);        SnowflakeKeyGenerator.setMaxTolerateTimeDifferenceMilliseconds(maxTolerateTime);        return new SnowflakeKeyGenerator();    }}

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