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<h1>Commit-Time Callbacks</h1><p>Commit-time callbacks were introduced in db4o version 6.2.</p>
<p>Commit-time callbacks allow a user to add some specific
behavior just before and just after a transaction is committed. </p>
<p>Typical use-cases for commit-time callbacks:</p>
<ul><li>add constraint-violation checking before commit;</li><li>check application-specific conditions before commit is done;</li><li>start synchronization or backup after commit;</li><li>notify other clients/applications about
successful/unsuccessful commit.</li></ul>
<p>Commit-time callbacks can be triggered by the following 2 events:<b></b></p><ul><li><b>Committing</b>: event
subscribers are notified before the container starts any meaningful commit
work and are allowed to cancel the entire operation by throwing an
exception; the ObjectContainer instance is completely blocked while
subscribers are being notified which is both a blessing because
subscribers can count on a stable and safe environment and a curse because
it prevents any parallelism with the container;</li><li><b>Committed</b>:
event subscribers are notified in a separate thread after the container has completely
finished the commit operation; exceptions if any will be ignored.
</li></ul>
<p> <div class="childTopicList">More Reading:<ul>
<li><p><a href="commit-time_callbacks/how_to_use_commit-time_callbacks.html" class="wikiLink">How To Use Commit-Time Callbacks</a></p></li>
<li><p><a href="commit-time_callbacks/committing_event_example.html" class="wikiLink">Committing Event Example</a></p></li>
<li><p><a href="commit-time_callbacks/committed_event_example.html" class="wikiLink">Committed Event Example</a></p></li>
<li><p><a href="commit-time_callbacks/car.html" class="wikiLink">Car</a></p></li>
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This revision (2) was last Modified 2007-05-02T15:36:25 by Tetyana.
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