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Caching Best Practices
Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!
When moving from JPA to MongoDB you start to realize how many JPA features you’ve previously taken for granted. JPA prevents “lost updates” through both pessimistic and optimistic locking. Optimistic locking doesn’t end up locking anything, and it would have been better named optimistic locking-free or optimistic concurrency control because that’s what it does anyway.
So, what does it mean to “lose updates”?
A real-life example would be when multiple background tasks update different attributes of some common Entity.
In our example, we have a Product Entity with a quantity and a discount which are resolved by two separate batch processors.
In JPA you may provide the @Version field (usually an auto-incremented number) and Hibernate takes care of the rest. Behind the scenes there is a safety mechanism that checks the updated rows number when given a specific version. If no row was updated, then the version has changed and an optimistic locking exception is thrown.
UPDATE Product SET quantity=1, discount=15 WHERE version=1;
But if your storage is not a relational database system but a NoSQL database instead, you still want to prevent lost updates. Luckily Spring Data comes to the rescue, as it provides a set of Document-oriented annotations, among which you can find a @Version annotation with the same semantic as its JPA counterpart.
If you enjoyed this article, I bet you are going to love my upcoming Online Workshops!
- Caching Best Practices with JPA and Hibernate (2.5 hours) on the 30th of September
- High-Performance SQL (4 hours) on the 6th of October in collaboration with Voxxed Days Ticino
- High-Performance SQL (12 hours) starting on the 28th of October in collaboration with Bouvet
An automatic retry mechanism should also be employed, as an optimistic locking exception is a recoverable one. It only needs to reload the latest Entity snapshot, merge the specific attributes and update.
So, Spring Data offers more than base repository support and simple query automation. The optimistic locking add-on provides the proper level of write consistency required by your application requirements.
Code available on GitHub
Hypersistence Optimizer 2.2 has been released!