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Globally Unique ID Generator

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This project is a Java implementation of the Go Lang library found here: https://github.com/rs/xid

Description

Xid is a globally unique id generator library. They are small, fast to generate and ordered.

Xid uses the Mongo Object ID algorithm to generate globally unique ids with a different serialization (base32) to make it shorter when transported as a string: https://docs.mongodb.org/manual/reference/object-id/

<table border="1"> <caption>Xid layout</caption> <tr> <td>0</td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td><td>6</td><td>7</td><td>8</td><td>9</td><td>10</td><td>11</td> </tr> <tr> <td colspan="4">time</td><td colspan="5">random value</td><td colspan="3">inc</td> </tr> </table>

The binary representation of the id is compatible with Mongo 12 bytes Object IDs. The string representation is using base32 hex (w/o padding) for better space efficiency when stored in that form (20 bytes). The hex variant of base32 is used to retain the sortable property of the id.

Xids simply offer uniqueness and speed, but they are not cryptographically secure. They are predictable and can be brute forced given enough time.

Features

Comparison

NameBinary SizeString SizeFeatures
UUID16 bytes36 charsconfiguration free, not sortable
shortuuid16 bytes22 charsconfiguration free, not sortable
Snowflake8 bytesup to 20 charsneeds machine/DC configuration, needs central server, sortable
MongoID12 bytes24 charsconfiguration free, sortable
xid12 bytes20 charsconfiguration free, sortable

Installation

Gradle

dependencies {
    implementation 'com.github.0xshamil:java-xid:1.0.0'
}

Maven

<dependency>
  <groupId>com.github.0xshamil</groupId>
  <artifactId>java-xid</artifactId>
  <version>1.0.0</version>
</dependency>

Usage

Get Xid instance

final Xid xid = Xid.get(); 

System.out.println(xid.toString()); // 9m4e2mr0ui3e8a215n4g

as base32Hex String

final String xidStr = Xid.string(); // bt0j9l2s5bo37fcla7q0

as byte array:

final byte[] xidBytes = Xid.bytes(); 

to create an Xid from a specific date

final String d = "10-Aug-2020 09:43:29 +0000"; 
final String dateFormat  = "dd-MMM-yyyy HH:mm:ss Z";
Date date = new SimpleDateFormat(dateFormat).parse(d);
final Xid xid = new Xid(date);

System.out.println(xid.toString()); // bsohdgdl8njn9eimov6g
System.out.println(xid.getDate()); // Mon Aug 10 15:13:29 IST 2020
System.out.println(xid.getTimestamp()); // 1597052609

to construct back Xid from a hex string:

final Xid xid = new Xid("bsohdgdl8njn9eimov6g");

System.out.println(xid.getDate()); // Mon Aug 10 15:13:29 IST 2020
System.out.println(xid.getTimestamp()); // 1597052609

Licenses

The source code is licensed under the MIT License.