snowflake 不重复id代码生成类

2019-11-08 02:03:55

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不重复id代码生成类

package com.hp.snowflake;/** * An object that generates IDs. * This is broken into a separate class in case * we ever want to support multiple worker threads * per PRocess */public class IdWorker { private long workerId; private long datacenterId; private long sequence = 0L; private long twepoch = 1288834974657L; private long workerIdBits = 5L; private long datacenterIdBits = 5L; private long maxWorkerId = -1L ^ (-1L << workerIdBits); private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); private long sequenceBits = 12L; private long workerIdShift = sequenceBits; private long datacenterIdShift = sequenceBits + workerIdBits; private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits; private long sequenceMask = -1L ^ (-1L << sequenceBits); private long lastTimestamp = -1L; public IdWorker(long workerId, long datacenterId) { if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId)); } if (datacenterId > maxDatacenterId || datacenterId < 0) { throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId)); } this.workerId = workerId; this.datacenterId = datacenterId; } public synchronized long nextId() { long timestamp = timeGen(); if (timestamp < lastTimestamp) { throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp)); } if (lastTimestamp == timestamp) { sequence = (sequence + 1) & sequenceMask; if (sequence == 0) { timestamp = tilNextMillis(lastTimestamp); } } else { sequence = 0L; } lastTimestamp = timestamp; return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence; } protected long tilNextMillis(long lastTimestamp) { long timestamp = timeGen(); while (timestamp <= lastTimestamp) { timestamp = timeGen(); } return timestamp; } protected long timeGen() { return System.currentTimeMillis(); }}

多线程测试，生成是否有重复id

package com.hp.snowflake;import java.util.HashSet;import java.util.Set;public class IdWorkerTest { static class IdWorkThread implements Runnable { private Set<Long> set; private IdWorker idWorker; public IdWorkThread(Set<Long> set, IdWorker idWorker) { this.set = set; this.idWorker = idWorker; } @Override public void run() { while (true) { for(int x=0;x<10000;x++){ long id = idWorker.nextId(); if (!set.add(id)) { System.out.println("duplicate:" + id); } } } } } public static void main(String[] args) { Set<Long> set = new HashSet<Long>(); for(int x=0;x<31;x++){ final IdWorker idWorker1 = new IdWorker(x, x); Thread t1 = new Thread(new IdWorkThread(set, idWorker1)); t1.setDaemon(true); t1.start(); } }}

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