Grails使用UUID ID生成器生成的ID随机性不足问题咨询

Hey there, let's unpack why you're seeing those nearly identical UUID prefixes and get you set up with properly random UUIDs.

The Root Cause: Hibernate's Default UUID Strategy #

The issue here boils down to which UUID version Hibernate is using. By default, Hibernate's legacy uuid generator produces UUIDv1 values, not the fully random UUIDv4 you're expecting.

UUIDv1 is built from:

• A timestamp (the first 60 bits)
• A MAC address of the machine generating it

Since you created all 4 instances in quick succession, the timestamp portion is almost identical—hence the repeated prefixes you see. UUIDv1 isn't designed for randomness; it's built to guarantee uniqueness across different machines.

How to Switch to Random UUIDv4 #

You need to explicitly configure Hibernate to use UUIDv4. Here are the steps tailored to your Grails 4 + Hibernate 7.0.4 setup:

Option 1: Configure in Your Grails Domain Class

If you're using Grails domain classes, update the mapping block to use the uuid2 generator (which produces UUIDv4):

class MsgTemplate {
    UUID id
    String ttag
    String name

    static mapping = {
        id generator: 'uuid2', type: 'uuid-char' // 'uuid-char' maps to PostgreSQL's uuid type
    }
}

Option 2: Use JPA/Hibernate Annotations (for pure JPA entities)

If you're working with JPA entities directly, use Hibernate's @UuidGenerator annotation to specify random style:

import org.hibernate.annotations.UuidGenerator;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;

@Entity
public class MsgTemplate {
    @Id
    @GeneratedValue
    @UuidGenerator(style = UuidGenerator.Style.RANDOM) // Generates UUIDv4
    private UUID id;

    // ... other fields
}

Or if you prefer JPA's standard GenerationType.UUID (available in JPA 3.0+, which Hibernate 7 supports):

@Id
@GeneratedValue(strategy = GenerationType.UUID)
private UUID id;

Bonus: Verify PostgreSQL Compatibility #

Make sure your id column in PostgreSQL is of type uuid (not varchar). Grails' type: 'uuid-char' will handle this correctly, or you can explicitly define the column type in your mapping if needed.

With these changes, your generated UUIDs will be fully random (UUIDv4) and no longer share identical prefixes across quickly created instances.

内容的提问来源于stack exchange，提问作者sodastream