JAVA 實現雪花算法生成惟一訂單號工具類

import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;

import java.util.Calendar;

/**
 * Default distributed primary key generator.
 * 
 * <p>
 * Use snowflake algorithm. Length is 64 bit.
 * </p>
 * 
 * <pre>
 * 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
 * </pre>
 * 
 * <p>
 * Call @{@code DefaultKeyGenerator.setWorkerId} to set worker id, default value is 0.
 * </p>
 * 
 * <p>
 * Call @{@code DefaultKeyGenerator.setMaxTolerateTimeDifferenceMilliseconds} to set max tolerate time difference milliseconds, default value is 0.
 * </p>
 * 
 * @author gaohongtao
 */
@Slf4j
public 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 #進程ID，每一個實例都要設置不一樣的值，範圍：0-1023
    maxTolerateTime: 1500 #最大容忍時鐘回退時間，單位：毫秒

若是mybati使用了plugins插件，能夠繼承進來

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();
    }
}