030 流水号的生成

　　公司的流水号生成规则有一个bug需要修复，顺便查查资料，看看人家都怎么做的，这里稍微整理了一些。

一：第一种方式

1.需求加分析

　　日期+ long（商家Id+订单类型+主机ID+AtomicInteger），什么意思呢，前面的日期保持不变，后面的将商家Id,订单的类型，主机的Id，AtomicInteger，通过移位与或运算“保存”到一个long类型里面。为什么要这么做？

1. 不想把相关信息直接暴露出去。
2. 通过流水号可以快速得到相关业务信息，快速定位问题。
3. 使用AtomicInteger可提高并发量，降低了冲突。

2.原理

　　

1. 符号位，这个不用过的介绍，大家都知道2进制第一位都是符号位，0表示正数1表示负数
2. 当前秒数，表述的是当前是当天的第多少秒，每天最多有86400秒，最多占17位
3. 商家Id占14位，由于业务涉及到商户，订单也是归为每个商户下面的，假定我们的最多有9999家商户，9999占位是14位，所以我们商户Id占14位，大家根据自身业务的量来决定长度。
4. 订单类型，假定我们的订单类型还停留在10种以内，所以我们保留4位，最多支持类型16种，大家同样的根据业务的量来决定
5. 服务器的Id，假定服务器数量在10台以内，所以我们保留4位，最多支持16台服务器，大家同样的根据自身服务器的数量来决定。，
6. 剩下的24位全部留给AtomicInteger，设计上我这里的qps可以达到2的24方。这个其实已经很大了。大家根据上面的设计留下来的数量当AtomicInteger位数，其实可以满足大部分业务需求了。

 3.程序大纲

　　

4.TimeUtil.java

package com.jun.it;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class TimeUtil {
    public static final String DATE_FORMAT_PATTERN_DEFAULT = "yyyy-MM-dd HH:mm:ss";
    public static final String DATE_FORMAT_PATTERN_NO_SECOND = "yyyy-MM-dd HH:mm";
    public static final String DATE_FORMAT_PATTERN_HTTP = "EEE, dd-MMM-yyyy HH:mm:ss z";
    public static final String DATE_FORMAT_PATTERN_SHORT = "yyyy-MM-dd";
    public static final String DATE_FORMAT_PATTERN_INT = "yyyyMMdd";
    public static final String DATE_FORMAT_PATTERN_NO_SEPARATOR = "yyyyMMddHHmmss";
    public static final String DATE_FORMAT_PATTERN_MONTH_INT = "yyyyMM";

    public static int toSeconds() {
        return (int) (System.currentTimeMillis() / 1000);
    }

    public static int toSeconds(Date date) {
        if (date != null) {
            return (int) (date.getTime() / 1000);
        }
        return 0;
    }


    public static Date floor(Date date) {
        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        return calendar.getTime();
    }

    public static Date ceiling(Date date) {
        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date);
        calendar.set(Calendar.HOUR_OF_DAY, 23);
        calendar.set(Calendar.MINUTE, 59);
        calendar.set(Calendar.SECOND, 59);
        calendar.set(Calendar.MILLISECOND, 999);
        return calendar.getTime();
    }

    public static String format(Date date, String formatString) {
        if (date == null) {
            date = new Date();
        }
        return new SimpleDateFormat(formatString).format(date);
    }

    public static int toInt(Date date) {
        if (date != null) {
            return Integer.parseInt(format(date, DATE_FORMAT_PATTERN_INT));
        }
        return 0;
    }

    public static Date now() {
        return new Date();
    }


    public static void main(String[] args) {
        System.out.println(floor(new Date()));
        System.out.println(ceiling(new Date()));
        System.out.println(now());
        System.out.println(toInt(new Date()));
    }
}

5.SerialNumberDemo.java

　　这里的方式是优雅了许多，是通过移位，然后或的方式拼接而成。

package com.jun.it;

import java.util.Date;
import java.util.concurrent.atomic.AtomicInteger;

public class SerialNumberDemo {
     private static final AtomicInteger SERIAL = new AtomicInteger(Integer.MAX_VALUE);
        private static final int SHIFTS_FOR_TIMESTAMP = 17;
        private static final int SHIFTS_FOR_UNION = 14;
        private static final int SHIFTS_FOR_TYPE = 4;
        private static final int SHIFTS_FOR_NODE = 4;
        private static final int SHIFTS_FOR_SERIAL = 24;
        private static final int MASK_FOR_SERIAL = (1 << SHIFTS_FOR_SERIAL) - 1;
        private static final long MASK_FOR_UNION = (1 << SHIFTS_FOR_UNION) - 1;
        private static final long MASK_FOR_TYPE = (1 << SHIFTS_FOR_TYPE) - 1;

        public static String next(long mechId, long type) {
            long second = TimeUtil.toSeconds() - TimeUtil.toSeconds(TimeUtil.floor(new Date()));
            long serverId = 1; //这个地方应该可以根据tomcat参数来设置的，通过或tomcat参数来获取服务器id
            long serial = SERIAL.incrementAndGet();
            long secondShift = second << (64 - 1 - SHIFTS_FOR_TIMESTAMP);
            long unionShift = mechId << (64 - 1 - SHIFTS_FOR_TIMESTAMP - SHIFTS_FOR_UNION);
            long typeShift = type << (64 - 1 - SHIFTS_FOR_TIMESTAMP - SHIFTS_FOR_UNION - SHIFTS_FOR_TYPE);
            long nodeShift = serverId << (64 - 1 - SHIFTS_FOR_TIMESTAMP - SHIFTS_FOR_UNION - SHIFTS_FOR_TYPE - SHIFTS_FOR_NODE);
            long number = secondShift | unionShift | typeShift | nodeShift | (serial & MASK_FOR_SERIAL);
            return String.valueOf(TimeUtil.toInt(new Date())) + String.valueOf(number);
        }

        public static long getSecond(long id) {
            return id >> (SHIFTS_FOR_UNION + SHIFTS_FOR_TYPE + SHIFTS_FOR_NODE + SHIFTS_FOR_SERIAL);
        }

        public static long getMechId(long id) {
            return (id >> (SHIFTS_FOR_TYPE + SHIFTS_FOR_NODE + SHIFTS_FOR_SERIAL)) & MASK_FOR_UNION;
        }

        public static long getType(long id) {
            return (id >> (SHIFTS_FOR_NODE + SHIFTS_FOR_SERIAL)) & MASK_FOR_TYPE;
        }


        public static void main(String[] args) {
            String number = next(14, 4);
            System.out.println(number);  
            System.out.println("秒数："+getSecond(5709508857563185152L));
            System.out.println("商户Id："+getMechId(5709508857563185152L));
            System.out.println("订单类型："+getType(5709508857563185152L));
        }
}

6.效果

　　

二：