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.
*
* <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 #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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