生成随机单据号

背景：全局生成4位字符2222-9ZZ9

实现方式：

使用redis的原子自增 + google的retry保证，生成4位数

1、pom

<dependency>
    <groupId>com.github.rholder</groupId>
    <artifactId>guava-retrying</artifactId>
    <version>2.0.0</version>
</dependency>

2、获取单号序列重试器

    private final Retryer<Long> getOrderSequenceRetryer = RetryerBuilder.<Long>newBuilder()
            .retryIfResult(Objects::isNull).retryIfException()
            .withWaitStrategy(WaitStrategies.incrementingWait(30, TimeUnit.MILLISECONDS, 10, TimeUnit.MILLISECONDS))
            .withStopStrategy(StopStrategies.stopAfterAttempt(2)).build();

3、redis原子自增 + guava的重试机制保证

private String getFallbackSuffix() {
        Long num;
        try {
            num = getOrderSequenceRetryer.call(
                    () -> redisGateway.incr()//使用redis的原子自增+1，并设置过期时间
            );
        } catch (Exception e) {
            throw new RuntimeException("redis incr exception", e);
        }
        return getSuffix(num.intValue());
    }

4、将生成的原子自增数，取后缀，最终4位范围【2222-9ZZ9】和业务相关

     /**
     * 获取后缀
     * [(2-9), (2-9,A-H,J-N,P-Z), 2-9,A-H,J-N,P-Z), (2-9)]
     * 2222-9ZZ9
     *
     * @param num num
     * @return suffix
     */
    public static String getSuffix(int num) {

        String[] suffixFactors = new String[]{"2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F",
                "G", "H", "J", "K", "L", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"};
        // 65536 = 8 * 32 * 32 * 8
        int serialNumberThreshold = 65536;
        if (num >= 0 && num < serialNumberThreshold) {
            int index4 = num / 8192;
            int mod4 = num % 8192;
            int index3 = mod4 / 256;
            int mod3 = mod4 % 256;
            int index2 = mod3 / 8;
            int mod2 = mod3 % 8;
            return suffixFactors[index4] + suffixFactors[index3] + suffixFactors[index2] + suffixFactors[mod2];
        }
        throw new IllegalArgumentException("num 超过流水号阈值,单号可能会重复!!!");
    }

注意事项

1、单据号中，最好不要说使用1和l，0和o（数字只能用8个，字母只能用大写的24个）

2、guava的重试机制参考：

https://zzzgd.blog.csdn.net/article/details/84377962?spm=1001.2101.3001.6650.1&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-1.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-1.pc_relevant_default&utm_relevant_index=2

UUID

public class IdUtil {
	/*
	 * 返回使用ThreadLocalRandom的UUID，比默认的UUID性能更优
	 */
	public static UUID fastUUID() {
		ThreadLocalRandom random = ThreadLocalRandom.current();
		return new UUID(random.nextLong(), random.nextLong());
	}
}

随机生成前缀 + 日期 + 后缀随机5位数

    private static final DateTimeFormatter FORMATTER_DATE_YYYYMMDDHHMMSS = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");

    @Test
    public void t() throws Exception {
        String suffix = StringUtils.leftPad(String.valueOf(new Random().nextInt(100)), 5, "0");
        String result = "prefix" + formatLocalDateTime(LocalDateTime.now()) + suffix;
    }

    public static String formatLocalDateTime(LocalDateTime localDateTime) {
        return FORMATTER_DATE_YYYYMMDDHHMMSS.format(localDateTime);
    }