生成uuid

时间 2019-11-10

标签生成 uuid 繁體版

原文原文链接

Base64压缩UUID长度替换Hibernate原有UUID生成器

本文来自http://my.oschina.net/noahxiao/blog/132277，我的储藏使用html

一、背景

在采用Hibernate作对象映射时，我一直都采用UUID来作主键。因为Hibernate的UUID须要占用32位的字符，因此通常都会让人感受响效率且增长存储占用。java

我在查看公司项目时发现了一种比较好的生成UUID的方法，就是将UUID数据进行Base64化。以为比较有意义拿出来给你们分享。git

二、传统UUID

a、java.util.UUID

Java中的UUID采用RFC 4122的标准，按标准数据按16进制进行表示（36个字符）。如：f81d4fae-7dec-11d0-a765-00a0c91e6bf6apache

b、Hibernate UUID

Hibernate默认产生的UUID与RFC 4122标准相比，去掉了没有用的"-"分割符号，因此更短（32个字符）。如：f81d4fae7dec11d0a76500a0c91e6bf6安全

三、Base64格式的UUID

因为Base64编码使用的字符包括大小写字母各26个，加上10个数字，和加号“+”，斜杠“/”，一共64个字符。因此才有Base64名字的由来。Base64至关于使用64进制来表示数据，相同长度位数的状况下要比16进制表示更多的内容。session

因为UUID标准数据总共是128-bit，因此咱们就能够对这个128-bit从新进行Base64编码。app

128-bit的UUID在Java中表示为两个long型数据，能够采用java.util.UUID中的 getLeastSignificantBits与getMostSignificantBits分别得到两个long（64-bit）。再经过 Base64转码就能够得到咱们所要的UUID。dom

UuidUtils工具类ide

package org.noahx.uuid; import org.apache.commons.codec.binary.Base64; import java.util.UUID; public abstract class UuidUtils { public static String uuid() { UUID uuid = UUID.randomUUID(); return uuid.toString(); } public static String compressedUuid() { UUID uuid = UUID.randomUUID(); return compressedUUID(uuid); } protected static String compressedUUID(UUID uuid) { byte[] byUuid = new byte[16]; long least = uuid.getLeastSignificantBits(); long most = uuid.getMostSignificantBits(); long2bytes(most, byUuid, 0); long2bytes(least, byUuid, 8); String compressUUID = Base64.encodeBase64URLSafeString(byUuid); return compressUUID; } protected static void long2bytes(long value, byte[] bytes, int offset) { for (int i = 7; i > -1; i--) { bytes[offset++] = (byte) ((value >> 8 * i) & 0xFF); } } public static String compress(String uuidString) { UUID uuid = UUID.fromString(uuidString); return compressedUUID(uuid); } public static String uncompress(String compressedUuid) { if (compressedUuid.length() != 22) { throw new IllegalArgumentException("Invalid uuid!"); } byte[] byUuid = Base64.decodeBase64(compressedUuid + "=="); long most = bytes2long(byUuid, 0); long least = bytes2long(byUuid, 8); UUID uuid = new UUID(most, least); return uuid.toString(); } protected static long bytes2long(byte[] bytes, int offset) { long value = 0; for (int i = 7; i > -1; i--) { value |= (((long) bytes[offset++]) & 0xFF) << 8 * i; } return value; } }

经过调用UuidUtils.compressedUuid()方法就能够得到个人须要的UUID字符串（22个字符，128-bit的Base64只须要22个字符）。如：BwcyZLfGTACTz9_JUxSnyA工具

比Hibernate32个字符还短了10个字符。

在处理Base64时，这里用到了apache的commons-codec编码工具包，由于它提供了简单的编码转换方法。并且还有 encodeBase64URLSafeString方法，采用URL安全方式生成Base64编码。默认的Base64含有+与/字符，若是这种编码出如今URL中将形成混乱。URL安全方式采用了-替换+，_替换/，并去掉告终束==。很是适合Web直接传参。

四、Hibernate的UUID生成器

因为Hibernate4对SessionImplementor的包作出了调整因此ID生成器的实现稍有不一样（import）。

a、Hibernate3

package org.noahx.uuid; import org.hibernate.HibernateException; import org.hibernate.engine.SessionImplementor; import org.hibernate.id.IdentifierGenerator; import java.io.Serializable; public class Base64UuidGenerator implements IdentifierGenerator { @Override public Serializable generate(SessionImplementor session, Object object) throws HibernateException { return UuidUtils.compressedUuid(); } }

b、Hibernate4

package org.noahx.uuid; import org.hibernate.HibernateException; import org.hibernate.engine.spi.SessionImplementor; import org.hibernate.id.IdentifierGenerator; import java.io.Serializable; public class Base64UuidGenerator implements IdentifierGenerator { @Override public Serializable generate(SessionImplementor session, Object object) throws HibernateException { return UuidUtils.compressedUuid(); } }

映射中使用Base64的UUID

@Id
    @GenericGenerator(name = "uuidGenerator", strategy = "org.noahx.uuid.Base64UuidGenerator")
    @GeneratedValue(generator = "uuidGenerator")
    @Column("UUID", length = 22)
    private String uuid;

Base58简介

Base58采用的字符集合为 “123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ”，从这不难看出，Base58是纯数字与字母组成并且去掉了容易引发视觉混淆的字符（0：数字零，O：大写O，I：大写i，l:小写L）。9个数字+49个字母=58 个。因为没有特殊字符因此在采用鼠标双击或移动设备选择时能够自动识别全选。

Base58自己就是URLSafe。Base64的URFSafe模式虽然已经对URL支持的比较好，但UUID中仍是包含“-或_”。

目前流行的比特币，采用的就是Base58Check编码，是在Base58基础上又增长了安全效验机制。

3、Base58编码器程序

因为Base58最近才兴起，Java与Apache Commons中并不包含编码器。

package org.noahx.uuid.utils; import java.io.UnsupportedEncodingException; import java.math.BigInteger; /** * Created with IntelliJ IDEA. * User: noah * Date: 8/2/13 * Time: 10:36 AM * To change this template use File | Settings | File Templates. */ public class Base58 { public static final char[] ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray(); private static final int[] INDEXES = new int[128]; static { for (int i = 0; i < INDEXES.length; i++) { INDEXES[i] = -1; } for (int i = 0; i < ALPHABET.length; i++) { INDEXES[ALPHABET[i]] = i; } } /** * Encodes the given bytes in base58. No checksum is appended. */ public static String encode(byte[] input) { if (input.length == 0) { return ""; } input = copyOfRange(input, 0, input.length); // Count leading zeroes. int zeroCount = 0; while (zeroCount < input.length && input[zeroCount] == 0) { ++zeroCount; } // The actual encoding. byte[] temp = new byte[input.length * 2]; int j = temp.length; int startAt = zeroCount; while (startAt < input.length) { byte mod = divmod58(input, startAt); if (input[startAt] == 0) { ++startAt; } temp[--j] = (byte) ALPHABET[mod]; } // Strip extra '1' if there are some after decoding. while (j < temp.length && temp[j] == ALPHABET[0]) { ++j; } // Add as many leading '1' as there were leading zeros. while (--zeroCount >= 0) { temp[--j] = (byte) ALPHABET[0]; } byte[] output = copyOfRange(temp, j, temp.length); try { return new String(output, "US-ASCII"); } catch (UnsupportedEncodingException e) { throw new RuntimeException(e); // Cannot happen.  } } public static byte[] decode(String input) throws IllegalArgumentException { if (input.length() == 0) { return new byte[0]; } byte[] input58 = new byte[input.length()]; // Transform the String to a base58 byte sequence for (int i = 0; i < input.length(); ++i) { char c = input.charAt(i); int digit58 = -1; if (c >= 0 && c < 128) { digit58 = INDEXES[c]; } if (digit58 < 0) { throw new IllegalArgumentException("Illegal character " + c + " at " + i); } input58[i] = (byte) digit58; } // Count leading zeroes int zeroCount = 0; while (zeroCount < input58.length && input58[zeroCount] == 0) { ++zeroCount; } // The encoding byte[] temp = new byte[input.length()]; int j = temp.length; int startAt = zeroCount; while (startAt < input58.length) { byte mod = divmod256(input58, startAt); if (input58[startAt] == 0) { ++startAt; } temp[--j] = mod; } // Do no add extra leading zeroes, move j to first non null byte. while (j < temp.length && temp[j] == 0) { ++j; } return copyOfRange(temp, j - zeroCount, temp.length); } public static BigInteger decodeToBigInteger(String input) throws IllegalArgumentException { return new BigInteger(1, decode(input)); } // // number -> number / 58, returns number % 58 // private static byte divmod58(byte[] number, int startAt) { int remainder = 0; for (int i = startAt; i < number.length; i++) { int digit256 = (int) number[i] & 0xFF; int temp = remainder * 256 + digit256; number[i] = (byte) (temp / 58); remainder = temp % 58; } return (byte) remainder; } // // number -> number / 256, returns number % 256 // private static byte divmod256(byte[] number58, int startAt) { int remainder = 0; for (int i = startAt; i < number58.length; i++) { int digit58 = (int) number58[i] & 0xFF; int temp = remainder * 58 + digit58; number58[i] = (byte) (temp / 256); remainder = temp % 256; } return (byte) remainder; } private static byte[] copyOfRange(byte[] source, int from, int to) { byte[] range = new byte[to - from]; System.arraycopy(source, from, range, 0, range.length); return range; } }

UUID生成程序

这个生成UUID程序包含了Base64(URLSafe)与Base58两种编码。

package org.noahx.uuid.util; import org.apache.commons.codec.binary.Base64; import java.nio.ByteBuffer; import java.util.UUID; public abstract class UuidUtils { public static String uuid() { UUID uuid = UUID.randomUUID(); return uuid.toString(); } public static String base64Uuid() { UUID uuid = UUID.randomUUID(); return base64Uuid(uuid); } protected static String base64Uuid(UUID uuid) { ByteBuffer bb = ByteBuffer.wrap(new byte[16]); bb.putLong(uuid.getMostSignificantBits()); bb.putLong(uuid.getLeastSignificantBits()); return Base64.encodeBase64URLSafeString(bb.array()); } public static String encodeBase64Uuid(String uuidString) { UUID uuid = UUID.fromString(uuidString); return base64Uuid(uuid); } public static String decodeBase64Uuid(String compressedUuid) { byte[] byUuid = Base64.decodeBase64(compressedUuid); ByteBuffer bb = ByteBuffer.wrap(byUuid); UUID uuid = new UUID(bb.getLong(), bb.getLong()); return uuid.toString(); } public static String base58Uuid() { UUID uuid = UUID.randomUUID(); return base58Uuid(uuid); } protected static String base58Uuid(UUID uuid) { ByteBuffer bb = ByteBuffer.wrap(new byte[16]); bb.putLong(uuid.getMostSignificantBits()); bb.putLong(uuid.getLeastSignificantBits()); return Base58.encode(bb.array()); } public static String encodeBase58Uuid(String uuidString) { UUID uuid = UUID.fromString(uuidString); return base58Uuid(uuid); } public static String decodeBase58Uuid(String base58uuid) { byte[] byUuid = Base58.decode(base58uuid); ByteBuffer bb = ByteBuffer.wrap(byUuid); UUID uuid = new UUID(bb.getLong(), bb.getLong()); return uuid.toString(); } }

生成UUID的效果

一、Base64的效果

M0ISICCxQi6sP-KIq3kFOw
11YozyYYTvKmuUXpRDvoJA
KlZnS-MuT2m3d-the2chxg 8J3SC10AQzqZr6Im8V2xYA ES1UiFTGTHqn6ADU5YW0aw 1usa208oT1q7FitKbQHH5Q 53aDQZxKTGyqmKCzDnBwYQ SVVjViEoQXayWB9_JknKqQ fP6znJIAT1uGMN9HW5o8cw YR-2-kKmSOubhGr2LpFCgQ

能够看到有-与_字符。你们能够双击上面包含-的UUID，获得只选中部分的效果。

二、Base58的效果

MqJqC2rtZLkuHys6ed2Eai
QrS5w2t5etpRY3zTR1BAEJ
Qd6wcFFVz2ZSQb3voGGj8P
75bJdWMcEh6NhT51D5Uyju
2L7kTgsktxMBKLkfAo2iWC
UX2Twhbt1kstRziqc7iwCR
9tZNKCeR93taLHU6PVy8hN
HSn6JMibca4nG9URWokpwg
8eL4SNz2a4puEW8fD4njsG
GThFxPsdVUoZMfmKoEHwQX

Base58与Base64(URLSafe)同样也只需21或22个字符就能够标示128位的UUID数据。基本同样的长度，看上去更舒服，固然之后就采用Base58来生成UUID。配合Hibernate的UUID生成器