在Java中创建GUID的一些最佳方法是什么?
当前回答
其他答案都是正确的，尤其是斯蒂芬·C的这个答案。
走出Java
出于安全考虑，在Java中生成UUID值仅限于版本4(随机)。
如果你想要其他版本的uuid，一种方法是让你的Java应用程序通过调用JVM之外的方法来生成uuid:
Command-line utilityBundled with nearly every operating system. For example, uuidgen found in Mac OS X, BSD, and Linux. Database serverUse JDBC to retrieve a UUID generated on the database server.For example, the uuid-ossp extension often bundled with Postgres. That extension can generates Versions 1, 3, and 4 values and additionally a couple variations: uuid_generate_v1mc() – generates a version 1 UUID but uses a random multicast MAC address instead of the real MAC address of the computer. uuid_generate_v5(namespace uuid, name text) – generates a version 5 UUID, which works like a version 3 UUID except that SHA-1 is used as a hashing method. Web ServiceFor example, UUID Generator creates Versions 1 & 3 as well as nil values and GUID.
其他回答
在许多情况下，我们需要对象的全局UUID，特别是在事件驱动架构或事件源中，我们必须根据日期对事件进行排序，但我们不需要关于时间戳的完整信息。
在那里，我们可以使用ULID的一个实现，它是按字典顺序排序的。
格式与标准UUID不同，但仍然很简单:
example value: 01AN4Z07BY79KA1307SR9X4MV3
01AN4Z07BY 79KA1307SR9X4MV3
|----------| |----------------|
Timestamp Randomness
48bits 80bits
在许多语言中都有实现。
例如，在Java中，有一个简单的库。
代码示例:
import de.huxhorn.sulky.ulid.ULID;
ULID ulid = new ULID();
// with current timestamp
String newId = ulid.nextULID();
// with selected timestamp
String newId2 = ulid.nextULID(Instant
.parse("2021-12-01T00:00:00.00Z")
.toEpochMilli()
);
使用Spring，您还可以为ULID生成器创建Bean。
@Configuration
public class UUIDGeneratorConfig {
@Bean
public ULID ulidGenerator() {
return new ULID();
}
}
@Component
public class ULIDGenerator {
private final ULID ulid;
public ULIDGenerator(ULID ulid) {
this.ulid = ulid;
}
public String generateUUID() {
return ulid.nextULID();
}
public String generateUUID(Instant timestamp) {
return ulid.nextULID(timestamp.toEpochMilli());
}
}
这取决于你想要什么样的UUID。
The standard Java UUID class generates Version 4 (random) UUIDs. (UPDATE - Version 3 (name) UUIDs can also be generated.) It can also handle other variants, though it cannot generate them. (In this case, "handle" means construct UUID instances from long, byte[] or String representations, and provide some appropriate accessors.) The Java UUID Generator (JUG) implementation purports to support "all 3 'official' types of UUID as defined by RFC-4122" ... though the RFC actually defines 4 types and mentions a 5th type.
关于UUID类型和变体的更多信息，维基百科中有一个很好的总结，RFC 4122和其他规范中有详细的信息。
这个答案包含2个生成器，用于基于随机和基于名称的uuid，符合RFC-4122。请随意使用和分享。
RANDOM-BASED (v4)
这个工具类生成基于随机的uuid:
package your.package.name;
import java.security.SecureRandom;
import java.util.Random;
import java.util.UUID;
/**
* Utility class that creates random-based UUIDs.
*
*/
public abstract class RandomUuidCreator {
private static final int RANDOM_VERSION = 4;
/**
* Returns a random-based UUID.
*
* It uses a thread local {@link SecureRandom}.
*
* @return a random-based UUID
*/
public static UUID getRandomUuid() {
return getRandomUuid(SecureRandomLazyHolder.THREAD_LOCAL_RANDOM.get());
}
/**
* Returns a random-based UUID.
*
* It uses any instance of {@link Random}.
*
* @return a random-based UUID
*/
public static UUID getRandomUuid(Random random) {
long msb = 0;
long lsb = 0;
// (3) set all bit randomly
if (random instanceof SecureRandom) {
// Faster for instances of SecureRandom
final byte[] bytes = new byte[16];
random.nextBytes(bytes);
msb = toNumber(bytes, 0, 8); // first 8 bytes for MSB
lsb = toNumber(bytes, 8, 16); // last 8 bytes for LSB
} else {
msb = random.nextLong(); // first 8 bytes for MSB
lsb = random.nextLong(); // last 8 bytes for LSB
}
// Apply version and variant bits (required for RFC-4122 compliance)
msb = (msb & 0xffffffffffff0fffL) | (RANDOM_VERSION & 0x0f) << 12; // apply version bits
lsb = (lsb & 0x3fffffffffffffffL) | 0x8000000000000000L; // apply variant bits
// Return the UUID
return new UUID(msb, lsb);
}
private static long toNumber(final byte[] bytes, final int start, final int length) {
long result = 0;
for (int i = start; i < length; i++) {
result = (result << 8) | (bytes[i] & 0xff);
}
return result;
}
// Holds thread local secure random
private static class SecureRandomLazyHolder {
static final ThreadLocal<Random> THREAD_LOCAL_RANDOM = ThreadLocal.withInitial(SecureRandom::new);
}
/**
* For tests!
*/
public static void main(String[] args) {
System.out.println("// Using thread local `java.security.SecureRandom` (DEFAULT)");
System.out.println("RandomUuidCreator.getRandomUuid()");
System.out.println();
for (int i = 0; i < 5; i++) {
System.out.println(RandomUuidCreator.getRandomUuid());
}
System.out.println();
System.out.println("// Using `java.util.Random` (FASTER)");
System.out.println("RandomUuidCreator.getRandomUuid(new Random())");
System.out.println();
Random random = new Random();
for (int i = 0; i < 5; i++) {
System.out.println(RandomUuidCreator.getRandomUuid(random));
}
}
}
输出如下:
// Using thread local `java.security.SecureRandom` (DEFAULT)
RandomUuidCreator.getRandomUuid()
'ef4f5ad2-8147-46cb-8389-c2b8c3ef6b10'
'adc0305a-df29-4f08-9d73-800fde2048f0'
'4b794b59-bff8-4013-b656-5d34c33f4ce3'
'22517093-ee24-4120-96a5-ecee943992d1'
'899fb1fb-3e3d-4026-85a8-8a2d274a10cb'
// Using `java.util.Random` (FASTER)
RandomUuidCreator.getRandomUuid(new Random())
'4dabbbc2-fcb2-4074-a91c-5e2977a5bbf8'
'078ec231-88bc-4d74-9774-96c0b820ceda'
'726638fa-69a6-4a18-b09f-5fd2a708059b'
'15616ebe-1dfd-4f5c-b2ed-cea0ac1ad823'
'affa31ad-5e55-4cde-8232-cddd4931923a'
基于name的(v3和v5)
生成基于名称的uuid (MD5和SHA1)的实用程序类:
package your.package.name;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.UUID;
/**
* Utility class that creates UUIDv3 (MD5) and UUIDv5 (SHA1).
*
*/
public class HashUuidCreator {
// Domain Name System
public static final UUID NAMESPACE_DNS = new UUID(0x6ba7b8109dad11d1L, 0x80b400c04fd430c8L);
// Uniform Resource Locator
public static final UUID NAMESPACE_URL = new UUID(0x6ba7b8119dad11d1L, 0x80b400c04fd430c8L);
// ISO Object ID
public static final UUID NAMESPACE_ISO_OID = new UUID(0x6ba7b8129dad11d1L, 0x80b400c04fd430c8L);
// X.500 Distinguished Name
public static final UUID NAMESPACE_X500_DN = new UUID(0x6ba7b8149dad11d1L, 0x80b400c04fd430c8L);
private static final int VERSION_3 = 3; // UUIDv3 MD5
private static final int VERSION_5 = 5; // UUIDv5 SHA1
private static final String MESSAGE_DIGEST_MD5 = "MD5"; // UUIDv3
private static final String MESSAGE_DIGEST_SHA1 = "SHA-1"; // UUIDv5
private static UUID getHashUuid(UUID namespace, String name, String algorithm, int version) {
final byte[] hash;
final MessageDigest hasher;
try {
// Instantiate a message digest for the chosen algorithm
hasher = MessageDigest.getInstance(algorithm);
// Insert name space if NOT NULL
if (namespace != null) {
hasher.update(toBytes(namespace.getMostSignificantBits()));
hasher.update(toBytes(namespace.getLeastSignificantBits()));
}
// Generate the hash
hash = hasher.digest(name.getBytes(StandardCharsets.UTF_8));
// Split the hash into two parts: MSB and LSB
long msb = toNumber(hash, 0, 8); // first 8 bytes for MSB
long lsb = toNumber(hash, 8, 16); // last 8 bytes for LSB
// Apply version and variant bits (required for RFC-4122 compliance)
msb = (msb & 0xffffffffffff0fffL) | (version & 0x0f) << 12; // apply version bits
lsb = (lsb & 0x3fffffffffffffffL) | 0x8000000000000000L; // apply variant bits
// Return the UUID
return new UUID(msb, lsb);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("Message digest algorithm not supported.");
}
}
public static UUID getMd5Uuid(String string) {
return getHashUuid(null, string, MESSAGE_DIGEST_MD5, VERSION_3);
}
public static UUID getSha1Uuid(String string) {
return getHashUuid(null, string, MESSAGE_DIGEST_SHA1, VERSION_5);
}
public static UUID getMd5Uuid(UUID namespace, String string) {
return getHashUuid(namespace, string, MESSAGE_DIGEST_MD5, VERSION_3);
}
public static UUID getSha1Uuid(UUID namespace, String string) {
return getHashUuid(namespace, string, MESSAGE_DIGEST_SHA1, VERSION_5);
}
private static byte[] toBytes(final long number) {
return new byte[] { (byte) (number >>> 56), (byte) (number >>> 48), (byte) (number >>> 40),
(byte) (number >>> 32), (byte) (number >>> 24), (byte) (number >>> 16), (byte) (number >>> 8),
(byte) (number) };
}
private static long toNumber(final byte[] bytes, final int start, final int length) {
long result = 0;
for (int i = start; i < length; i++) {
result = (result << 8) | (bytes[i] & 0xff);
}
return result;
}
/**
* For tests!
*/
public static void main(String[] args) {
String string = "JUST_A_TEST_STRING";
UUID namespace = UUID.randomUUID(); // A custom name space
System.out.println("Java's generator");
System.out.println("UUID.nameUUIDFromBytes(): '" + UUID.nameUUIDFromBytes(string.getBytes()) + "'");
System.out.println();
System.out.println("This generator");
System.out.println("HashUuidCreator.getMd5Uuid(): '" + HashUuidCreator.getMd5Uuid(string) + "'");
System.out.println("HashUuidCreator.getSha1Uuid(): '" + HashUuidCreator.getSha1Uuid(string) + "'");
System.out.println();
System.out.println("This generator WITH name space");
System.out.println("HashUuidCreator.getMd5Uuid(): '" + HashUuidCreator.getMd5Uuid(namespace, string) + "'");
System.out.println("HashUuidCreator.getSha1Uuid(): '" + HashUuidCreator.getSha1Uuid(namespace, string) + "'");
}
}
输出如下:
// Java's generator
UUID.nameUUIDFromBytes(): '9e120341-627f-32be-8393-58b5d655b751'
// This generator
HashUuidCreator.getMd5Uuid(): '9e120341-627f-32be-8393-58b5d655b751'
HashUuidCreator.getSha1Uuid(): 'e4586bed-032a-5ae6-9883-331cd94c4ffa'
// This generator WITH name space
HashUuidCreator.getMd5Uuid(): '2b098683-03c9-3ed8-9426-cf5c81ab1f9f'
HashUuidCreator.getSha1Uuid(): '1ef568c7-726b-58cc-a72a-7df173463bbb'
备用发电机
您还可以使用uuid-creator库。请看这些例子:
// Create a random-based UUID
UUID uuid = UuidCreator.getRandomBased();
// Create a name based UUID (SHA1)
String name = "JUST_A_TEST_STRING";
UUID uuid = UuidCreator.getNameBasedSha1(name);
项目页面:https://github.com/f4b6a3/uuid-creator
其他答案都是正确的，尤其是斯蒂芬·C的这个答案。
走出Java
出于安全考虑，在Java中生成UUID值仅限于版本4(随机)。
如果你想要其他版本的uuid，一种方法是让你的Java应用程序通过调用JVM之外的方法来生成uuid:
Command-line utilityBundled with nearly every operating system. For example, uuidgen found in Mac OS X, BSD, and Linux. Database serverUse JDBC to retrieve a UUID generated on the database server.For example, the uuid-ossp extension often bundled with Postgres. That extension can generates Versions 1, 3, and 4 values and additionally a couple variations: uuid_generate_v1mc() – generates a version 1 UUID but uses a random multicast MAC address instead of the real MAC address of the computer. uuid_generate_v5(namespace uuid, name text) – generates a version 5 UUID, which works like a version 3 UUID except that SHA-1 is used as a hashing method. Web ServiceFor example, UUID Generator creates Versions 1 & 3 as well as nil values and GUID.
用一个例子来扩展Mark Byers的回答:
import java.util.UUID;
public class RandomStringUUID {
public static void main(String[] args) {
UUID uuid = UUID.randomUUID();
System.out.println("UUID=" + uuid.toString() );
}
}
推荐文章
- 在Java中使用UUID的最重要位的碰撞可能性
- 转换列表的最佳方法:map还是foreach?
- 如何分割逗号分隔的字符串?
- Java字符串—查看字符串是否只包含数字而不包含字母
- Mockito.any()传递带有泛型的接口
- 在IntelliJ 10.5中运行测试时，出现“NoSuchMethodError: org.hamcrest. matcher . descripbemismatch”
- 使用String.split()和多个分隔符
- Java数组有最大大小吗?
- 在Android中将字符串转换为Uri
- 从JSON生成Java类?
- 为什么java.util.Set没有get(int index)?
- Swing和AWT的区别是什么?
- 为什么Java流是一次性的?
- 四舍五入BigDecimal *总是*有两位小数点后
- 设计模式:工厂vs工厂方法vs抽象工厂
