DATAMONGO-279 - optimistic locking based on version field

[noter]

This pull request contains optimistic locking implementation based on version field.

Changes:

added Version annotation with points to a version field
change save method on MongoTemplet to detect first time save or update.
If first save occure ((isNew() == true) and entity contains version filed then set this field to 0 and perform normal save.
If update occure (isNew() == false) then perform update with query by id and version and inc(version filed by one), then check writeConcern.getN() and throw OptimisticLockingFailureException if no documents was updated.

Any comments will be welcome.

[odrotbohm]

Very cool stuff. A tiny thing though: would you mind adding some code that binds the updated version to the current entity? Currently you have to manually load the entity to see the updated version number.

Another thought: would it make sense to update the version property in our code and then du a plain update with the former version constraint? That would solve the binding issue of the new version and probably simplify the construction of the update object a little as you don't have to add an inc(…) operation and manually exclude the version property from the update. As we change a single document only, the operation should be atomic anyway.

[noter]

Change completed.
Hope we don't go over long value in version :)
or do you have any other incrementation solution ?

[odrotbohm]

That looks pretty good now. I'll have a detailled look tomorrow, brush it up and might even integrate it already. Would make a nice a addition to the upcoming GA release. Would you mind filling out the contributors agreement and comment the id you get assigned? Thanks a ton already!

[noter]

My confirmation number is: 33320120907012713

[odrotbohm]

What's your name actually? Need it to polish up the JavaDoc (author tags etc.).

[noter]

Ah ok, I updated my account info. So it is Patryk Wasik.

[odrotbohm]

Polished and merged into master to be included in 1.1 GA. I've removed the MongoOperations enhancements and inlined the modified update(…) method. Added event triggering according to the ones used to from doSave(…).