Optimistic locking not throwing exception when manually setting version field

Question

I have a Spring Boot 1.3.M1 web application using Spring Data JPA. For optimistic locking, I am doing the following:

1. Annotate the version column in the entity:

Answer 1

Unfortunately, (at least for Hibernate) changing the @Version field manually is not going to make it another "version". i.e. Optimistic concurrency checking is done against the version value retrieved when entity is read, not the version field of entity when it is updated.

e.g.

This will work

Foo foo = fooRepo.findOne(id);  // assume version is 2 here
foo.setSomeField(....);

// Assume at this point of time someone else change the record in DB, 
// and incrementing version in DB to 3

fooRepo.flush();  // forcing an update, then Optimistic Concurrency exception will be thrown

However this will not work

Foo foo = fooRepo.findOne(id);  // assume version is 2 here
foo.setSomeField(....);
foo.setVersion(1);
fooRepo.flush();  // forcing an update, no optimistic concurrency exception
                  // Coz Hibernate is "smart" enough to use the original 2 for comparison

There are some way to workaround this. The most straight-forward way is probably by implementing optimistic concurrency check by yourself. I used to have a util to do the "DTO to Model" data population and I have put that version checking logic there. Another way is to put the logic in setVersion() which, instead of really setting the version, it do the version checking:

class User {
    private int version = 0;
    //.....

    public void setVersion(int version) {
        if (this.version != version) {
            throw new YourOwnOptimisticConcurrencyException();
        }
    }

    //.....
}