2.6.11. Using UUID generation

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As mentioned above, Hibernate supports UUID identifier value generation.
This is supported through its `org.hibernate.id.UUIDGenerator` id generator.

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`UUIDGenerator` supports pluggable strategies for exactly how the UUID is generated.
These strategies are defined by the `org.hibernate.id.UUIDGenerationStrategy` contract.
The default strategy is a version 4 (random) strategy according to IETF RFC 4122.
Hibernate does ship with an alternative strategy which is a RFC 4122 version 1 (time-based) strategy (using ip address rather than mac address).

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<div class="title">Example 121. Implicitly using the random UUID strategy</div>
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<pre class="prettyprint highlight">`@Entity
public class MyEntity {

    @Id
    @GeneratedValue
    public UUID id;

    ...
}`</pre>
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To specify an alternative generation strategy, we&#8217;d have to define some configuration via `@GenericGenerator`.
Here we choose the RFC 4122 version 1 compliant strategy named `org.hibernate.id.uuid.CustomVersionOneStrategy`

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<div class="title">Example 122. Implicitly using the random UUID strategy</div>
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<pre class="prettyprint highlight">`@Entity
public class MyEntity {

    @Id
    @GeneratedValue( generator = "uuid" )
    @GenericGenerator(
        name = "uuid",
        strategy = "org.hibernate.id.UUIDGenerator",
        parameters = {
            @Parameter(
                name = "uuid_gen_strategy_class",
                value = "org.hibernate.id.uuid.CustomVersionOneStrategy"
            )
        }
    )
    public UUID id;

    ...

}`</pre>
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