UUID with additional string as prefix in primary key Spring Boot - mysql

Question

I had an idea to implement UUID as my primary key in the SQL database with spring boot technology. Currently, I have a dilemma on how to implement a custom fixed string with UUID as my primary key. Here is an example:
This is a classic UUID:
08d88683-20fc-4884-a523-8f39a06d037f
But I wanted to my UUID looks something like this:
USER-08d88683-20fc-4884-a523-8f39a06d037f
How could I achieve that with Spring boot and Hibernate?
Here is my user model:
#Data
#Entity
#Table( name = "users",
uniqueConstraints = {
#UniqueConstraint(columnNames = "username"),
#UniqueConstraint(columnNames = "email")
})
#NoArgsConstructor
public class User {
#Id
#GeneratedValue(generator = "uuid2")
#GenericGenerator(name = "uuid2", strategy = "uuid2")
#Column(name = "id", updatable = false, nullable = false, columnDefinition = "VARCHAR(36)")
#Type(type = "uuid-char")
private UUID id;
#NotBlank
#Size(max = 20)
private String username;
#NotBlank
#Size(max = 50)
#Email
private String email;
#NotBlank
#Size(max = 120)
private String password;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable( name = "user_roles",
joinColumns = #JoinColumn(name = "user_id"),
inverseJoinColumns = #JoinColumn(name = "role_id"))
private Set<Role> roles = new HashSet<>();
public User(String username, String email, String password) {
this.username = username;
this.email = email;
this.password = password;
}
}

Answer 1

The best way to implement custom id generator in Hibernate.
Using the following class you can create Custom Generator:
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.IdentifierGenerator;
import java.io.Serializable;
import java.util.UUID;
public class CustomUserIdGenerator implements IdentifierGenerator {
#Override
public Serializable generate(SharedSessionContractImplementor sharedSessionContractImplementor, Object o) throws HibernateException {
return "USER-"+ UUID.randomUUID();
}
}
And then you can use the above created class as the generator strategy in entity class for the GenricGenerator
#Id
#GenericGenerator(name = "string_based_custom_sequence", strategy = "com.package.CustomUserIdGenerator")
#GeneratedValue(generator = "string_based_custom_sequence")
private UUID id;