IdGenerator 唯一Id生成器

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mob604756f06ed8 2020-06-11 18:09:00

文章标签 时间戳 i++ 自增序列号 文章分类 代码人生

public class IdGenerator {
private final static long beginTs = 1483200000000L;
private long lastTs = 0L;
private long processId;
private int processIdBits = 10;
private long sequence = 0L;
private int sequenceBits = 12;
public IdGenerator() {
}
public IdGenerator(long processId) {
if (processId > ((1 << processIdBits) - 1)) {
throw new RuntimeException("进程ID超出范围，设置位数" + processIdBits + "，最大" + ((1 << processIdBits) - 1));
}
this.processId = processId;
}
protected long timeGen() {
return System.currentTimeMillis();
}
public synchronized long nextId() {
long ts = timeGen();
// 刚刚生成的时间戳比上次的时间戳还小，出错
if (ts < lastTs) {
throw new RuntimeException("时间戳顺序错误");
}
// 刚刚生成的时间戳跟上次的时间戳一样，则需要生成一个sequence序列号
if (ts == lastTs) {
// sequence循环自增
sequence = (sequence + 1) & ((1 << sequenceBits) - 1);
// 如果sequence=0则需要重新生成时间戳
if (sequence == 0) {
// 且必须保证时间戳序列往后
ts = nextTs(lastTs);
}
// 如果ts>lastTs，时间戳序列已经不同了，此时可以不必生成sequence了，直接取0
} else {
sequence = 0L;
}
// 更新lastTs时间戳
lastTs = ts;
return ((ts - beginTs) << (processIdBits + sequenceBits)) | (processId << sequenceBits) | sequence;
}
public Long nextShortId() {
Long shortId = System.currentTimeMillis() / 100 % 1000000000;
if (shortId < 100000000) {
shortId += 100000000;
}
return shortId;
}
protected long nextTs(long lastTs) {
long ts = timeGen();
while (ts <= lastTs) {
ts = timeGen();
}
return ts;
}
}