UUID in Java and Spring Boot — v4, v7, and JPA Entity IDs

Java has included java.util.UUID since Java 1.5, making UUID v4 generation straightforward. UUID v7 support is newer — there is no UUID.timeBasedUUID() in the standard library yet, but the ecosystem has adapted quickly with Hibernate 6.5+, the JUG library, and upcoming JEP proposals.

Generating UUIDs in Java

UUID v4 (random) — standard library:

import java.util.UUID;

UUID id = UUID.randomUUID(); // v4
String str = id.toString();  // "550e8400-e29b-41d4-a716-446655440000"

UUID v7 — using java-uuid-generator (JUG):

<!-- pom.xml -->
<dependency>
  <groupId>com.fasterxml.uuid</groupId>
  <artifactId>java-uuid-generator</artifactId>
  <version>5.0.0</version>
</dependency>

import com.fasterxml.uuid.Generators;

UUID id = Generators.timeBasedEpochGenerator().generate(); // v7

JUG implements the RFC 9562 monotonic counter within each millisecond window, so rapid successive calls remain ordered even when the system clock has not advanced.

Spring Data JPA and UUID Primary Keys

Spring Boot auto-configures Hibernate, so JPA entity IDs map directly to database uuid columns (PostgreSQL) or BINARY(16) (MySQL) when using the correct annotations.

UUID v4 with @GeneratedValue:

@Entity
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.UUID)
    private UUID id;
}

GenerationType.UUID was added in Jakarta Persistence 3.1 (Spring Boot 3.1+). It delegates to Hibernate’s UUID generator, which defaults to v4.

UUID v7 with Hibernate 6.5+:

@Entity
public class Order {
    @Id
    @GeneratedValue
    @UuidGenerator(style = UuidGenerator.Style.TIME)
    private UUID id;
}

Style.TIME in Hibernate 6.5+ produces RFC 9562 v7 values. Earlier versions of Hibernate produced v1-style values — check your Hibernate version before relying on this annotation for v7.

Performance Considerations

The same B-tree index argument applies in Java as in other stacks: UUID v4 primary keys generate random inserts that fragment the clustered index over time. UUID v7 keeps inserts near the rightmost leaf page.

For PostgreSQL backends with Spring Data JPA, the difference is measurable at around 5–10 million rows. Switching to @UuidGenerator(style = UuidGenerator.Style.TIME) is a one-line change and requires no schema migration — the column type stays uuid.

MySQL with BINARY(16)

For MySQL backends, configure the uuid property mapping to BINARY(16):

@Entity
public class Order {
    @Id
    @Column(columnDefinition = "BINARY(16)")
    @GeneratedValue
    @UuidGenerator(style = UuidGenerator.Style.TIME)
    private UUID id;
}

Hibernate handles the UUID ↔ BINARY(16) conversion transparently. Queries using the ID will use the binary index efficiently.

Related Resources

• Hibernate 6.5 UUID Generator documentation
• java-uuid-generator (JUG) — UUID v7 for all Java versions
• Spring Data JPA reference documentation
• Jakarta Persistence 3.1 specification — defines GenerationType.UUID