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What is UUID in Hibernate?
Hibernate can also generate a UUID based on IETF RFC 4122 version 1. If you follow the specification, you should generate the UUID with the MAC address instead of the IP address. As long as nobody is messing around with it, the MAC address of each device should be unique and due to this help to create a unique UUID.
What is the primary key in an entity?
The primary key is an attribute or a set of attributes that uniquely identify a specific instance of an entity. Every entity in the data model must have a primary key whose values uniquely identify instances of the entity.
Can embeddable class be used as primary key?
An @Embedded field cannot contain Primary Key. If a Primary Key needs to be set as auto-generated, a single Primary Key may be used and defined as auto-generated in the @Entity data class.
Why are UUIDs used as primary keys in JPA?
If you implement equals and hashcode as above you also throw that one in as a bonus. UUID are Universal Unique (what’s in a name). This means that you get great flexibility if you need to copy/merge records from location a to b without having to re-generate keys. (or use complex sequence strategies).
What’s the difference between a UUID and a key?
UUID are Universal Unique (what’s in a name). This means that you get great flexibility if you need to copy/merge records from location a to b without having to re-generate keys. (or use complex sequence strategies). UUIDs are not guessable. This means it can be safer to expose them to the outside world in let’s say urls.
How to create a userid object in hibernate?
The most important part is the generate method. It will get a new unique long from the database, which we then use to create the UserId object. Hibernate will set this object on our User object. We can now use the UserIdIdentifierGenerator in our User entity: Note that we need to use @EmbeddedId instead of @Id.
Is it safe to expose UUIDs to the outside world?
UUIDs are not guessable. This means it can be safer to expose them to the outside world in let’s say urls. If this would be good practice is another thing.