10.3. Timestamp

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Timestamps are a less reliable way of optimistic locking than version numbers, but can be used by applications for other purposes as well.
Timestamping is automatically used if you the `@Version` annotation on a `Date` or `Calendar` property type.

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<div class="title">Example 277. Using timestamps for optimistic locking</div>
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<pre class="prettyprint highlight">`@Version
private Date version;`</pre>
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Hibernate can retrieve the timestamp value from the database or the JVM, by reading the value you specify for the `@org.hibernate.annotations.Source` annotation.
The value can be either `org.hibernate.annotations.SourceType.DB` or `org.hibernate.annotations.SourceType.VM`.
The default behavior is to use the database, and is also used if you don&#8217;t specify the annotation at all.

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The timestamp can also be generated by the database instead of Hibernate, if you use the `@org.hibernate.annotations.Generated(GenerationTime.ALWAYS)` annotation.

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