我如何得到的日期/时间回来从UUID 1型

问题描述 投票:0回答:1

我已经包括以下UUID库编译组:“com.fasterxml.uuid”,名称:“Java的UUID发电机”,版本:“3.1.5”在我的构建。

我有一些像这样的代码

        NoArgGenerator timeBasedGenerator = Generators.timeBasedGenerator()
        UUID tuid = timeBasedGenerator.generate()
        Timestamp timestamp = new Timestamp ((tuid.timestamp()/1000) as Long)
        Date dateTime = new Date (timestamp.getTime())

然而,当itry,并期待在日像它应该是什么,所以例如我得到“UID fef57eca-7c8b-11E8-BEDD-992c2ac3197a是太阳2月6七点55分54秒格林尼治标准时间6327”当今天是其分毫30/06 / 2018

有谁知道如何正确地提取使用fasterxml.uuid库基于时间的UUID真正的日期和时间?

但难倒

PS试过这种替代

        UUID tuid = timeBasedGenerator.generate()
        Long t = tuid.timestamp()
        Timestamp timestamp = new Timestamp (t)
        Date dateTime = new Date (timestamp.getTime())

这给周四的UID ff79d7d9-7cb5-11e8-976c-6ba57a5e9636和日期8月14日11时11分四十秒BST 4359073

java timeuuid
1个回答
1
投票

我做多一些在网络上搜索。

我建立了一个可扩展的需要以下“简单实用”类:

import com.fasterxml.uuid.Generators
import com.fasterxml.uuid.NoArgGenerator

class UuidUtil {

    static final NoArgGenerator timeBasedGenerator = Generators.timeBasedGenerator()


    /**
     * From UUID javadocs the resulting timestamp is measured in 100-nanosecond units since midnight, October 15, 1582 UTC
     * timestamp() from UUID is measured in 100-nanosecond units since midnight, October 15, 1582 UTC
     *
     * The Java timestamp in milliseconds since 1970-01-01 as baseline
     *
     * @return
     */
    static long getStartOfUuidRelativeToUnixEpochInMilliseconds () {
        Calendar c = Calendar.getInstance(TimeZone.getTimeZone("GMT-0"))
        c.set(Calendar.YEAR, 1582)
        c.set(Calendar.MONTH, Calendar.OCTOBER)
        c.set(Calendar.DAY_OF_MONTH, 15)
        c.set(Calendar.HOUR_OF_DAY, 0)
        c.set(Calendar.MINUTE, 0)
        c.set(Calendar.SECOND, 0)
        c.set(Calendar.MILLISECOND, 0)

        return c.getTimeInMillis()
    }

    //https://www.wolframalpha.com/input/?i=convert+1582-10-15+UTC+to+unix+time
    final static long START_OF_UUID_RELATIVE_TO_UNIX_EPOCH_SECONDS = -12219292800L
    final static long START_OF_UUID_RELATIVE_TO_UNIX_EPOCH_MILLIS = -12219292800L * 1000L

    /**
     * timestamp() from UUID is measured in 100-nanosecond units since midnight, October 15, 1582 UTC,
     * so we must convert for 100ns units to millisecond procession
     * @param tuid
     * @return
     */
    static long getMillisecondsFromUuid (UUID tuid) {

        assert tuid.version() == 1      //ensure its a time based UUID

        // timestamp returns in 10^-7 (100 nano second chunks), 
        // java Date constructor  assumes 10^-3 (millisecond precision)
        // so we have to divide by 10^4 (10,000) to get millisecond precision  
        long milliseconds_since_UUID_baseline = tuid.timestamp() /10000L

    }

    static getDateFromUuid (UUID tuid) {
        // Allocates a Date object and initializes it to represent the specified number of milliseconds since the 
        // standard java (unix) base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT
        // have to add relative offset from UUID start date of unix epoch to get start date in unix time milliseconds 
        new Date (getMillisecondsFromUuid (tuid) + START_OF_UUID_RELATIVE_TO_UNIX_EPOCH_MILLIS )
    }

    static UUID getTimeBasedUuid () {
        UUID tuid = timeBasedGenerator.generate()
    }

}

我已经添加了解释性注释,这样就可以跟着你不得不做处理UUID时间戳()方法为,对于普通的Java日期和时间处理工作的格式是什么。

为什么Java的UUID类不能提供人们所预料的,使基于时间的UUID与基于正常的Unix纪元普通的Java日期/时间格式互操作的方法是一个谜给我。

我使用上述静态方法跑一个小的测试脚本:

println "get start of epoch in milliseconds " + UuidUtil.getStartOfUuidRelativeToUnixEpochInMilliseconds()
assert UuidUtil.START_OF_UUID_RELATIVE_TO_UNIX_EPOCH_MILLIS == UuidUtil.startOfUuidRelativeToUnixEpochInMilliseconds

UUID tuid = UuidUtil.timeBasedUuid

println "uid : $tuid"

Date date = UuidUtil.getDateFromUuid(tuid)
println "extracted date from uid is " + UuidUtil.getDateFromUuid(tuid)

而得到这个

get start of epoch in milliseconds -12219292800000
uid : 43acb588-7d39-11e8-b37b-59f77bf2d333
extracted date from uid is Sun Jul 01 15:15:53 BST 2018

这看起来正确的时间运行脚本。

© www.soinside.com 2019 - 2024. All rights reserved.