package utils;import java.lang.management.ManagementFactory; import java.net.InetAddress; import java.net.NetworkInterface;/*** <p>名稱：IdWorker.java</p>* <p>描述：分布式自增長(zhǎng)ID</p>* <pre>* Twitter的 Snowflake　JAVA實(shí)現(xiàn)方案* </pre>* 核心代碼為其IdWorker這個(gè)類實(shí)現(xiàn)，其原理結(jié)構(gòu)如下，我分別用一個(gè)0表示一位，用—分割開部分的作用：* 1||0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000* 在上面的字符串中，第一位為未使用（實(shí)際上也可作為long的符號(hào)位），接下來(lái)的41位為毫秒級(jí)時(shí)間，* 然后5位datacenter標(biāo)識(shí)位，5位機(jī)器ID（并不算標(biāo)識(shí)符，實(shí)際是為線程標(biāo)識(shí)），* 然后12位該毫秒內(nèi)的當(dāng)前毫秒內(nèi)的計(jì)數(shù)，加起來(lái)剛好64位，為一個(gè)Long型。* 這樣的好處是，整體上按照時(shí)間自增排序，并且整個(gè)分布式系統(tǒng)內(nèi)不會(huì)產(chǎn)生ID碰撞（由datacenter和機(jī)器ID作區(qū)分），* 并且效率較高，經(jīng)測(cè)試，snowflake每秒能夠產(chǎn)生26萬(wàn)ID左右，完全滿足需要。* <p>* 64位ID (42(毫秒)+5(機(jī)器ID)+5(業(yè)務(wù)編碼)+12(重復(fù)累加))** @author Polim*/ public class IdWorker {// 時(shí)間起始標(biāo)記點(diǎn)，作為基準(zhǔn)，一般取系統(tǒng)的最近時(shí)間（一旦確定不能變動(dòng)）private final static long twepoch = 1288834974657L;// 機(jī)器標(biāo)識(shí)位數(shù)private final static long workerIdBits = 5L;// 數(shù)據(jù)中心標(biāo)識(shí)位數(shù)private final static long datacenterIdBits = 5L;// 機(jī)器ID最大值private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);// 數(shù)據(jù)中心ID最大值private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);// 毫秒內(nèi)自增位private final static long sequenceBits = 12L;// 機(jī)器ID偏左移12位private final static long workerIdShift = sequenceBits;// 數(shù)據(jù)中心ID左移17位private final static long datacenterIdShift = sequenceBits + workerIdBits;// 時(shí)間毫秒左移22位private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;private final static long sequenceMask = -1L ^ (-1L << sequenceBits);/* 上次生產(chǎn)id時(shí)間戳 */private static long lastTimestamp = -1L;// 0，并發(fā)控制private long sequence = 0L;private final long workerId;// 數(shù)據(jù)標(biāo)識(shí)id部分private final long datacenterId;public IdWorker(){this.datacenterId = getDatacenterId(maxDatacenterId);this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);}/*** @param workerId* 工作機(jī)器ID* @param datacenterId* 序列號(hào)*/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;}/*** 獲取下一個(gè)ID** @return*/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) {// 當(dāng)前毫秒內(nèi)，則+1sequence = (sequence + 1) & sequenceMask;if (sequence == 0) {// 當(dāng)前毫秒內(nèi)計(jì)數(shù)滿了，則等待下一秒timestamp = tilNextMillis(lastTimestamp);}} else {sequence = 0L;}lastTimestamp = timestamp;// ID偏移組合生成最終的ID，并返回IDlong nextId = ((timestamp - twepoch) << timestampLeftShift)| (datacenterId << datacenterIdShift)| (workerId << workerIdShift) | sequence;return nextId;}private long tilNextMillis(final long lastTimestamp) {long timestamp = this.timeGen();while (timestamp <= lastTimestamp) {timestamp = this.timeGen();}return timestamp;}private long timeGen() {return System.currentTimeMillis();}/*** <p>* 獲取 maxWorkerId* </p>*/protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {StringBuffer mpid = new StringBuffer();mpid.append(datacenterId);String name = ManagementFactory.getRuntimeMXBean().getName();if (!name.isEmpty()) {/** GET jvmPid*/mpid.append(name.split("@")[0]);}/** MAC + PID 的 hashcode 獲取16個(gè)低位*/return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);}/*** <p>* 數(shù)據(jù)標(biāo)識(shí)id部分* </p>*/protected static long getDatacenterId(long maxDatacenterId) {long id = 0L;try {InetAddress ip = InetAddress.getLocalHost();NetworkInterface network = NetworkInterface.getByInetAddress(ip);if (network == null) {id = 1L;} else {byte[] mac = network.getHardwareAddress();id = ((0x000000FF & (long) mac[mac.length - 1])| (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;id = id % (maxDatacenterId + 1);}} catch (Exception e) {System.out.println(" getDatacenterId: " + e.getMessage());}return id;}} 與50位技術(shù)專家面對(duì)面20年技術(shù)見證，附贈(zèng)技術(shù)全景圖

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