Question

I’m testing out Spring’s @Cacheable features with EHCache but I can’t find anything on whether this works with Spring’s @Transactional annotations.

I am placing @Cacheable and @CacheEvict on DAO methods while @Transactional are on service methods.

Suppose my User DAO looks like this:

@Cacheable(value="users", key="#id")
User find(BigInteger id);

@CacheEvict(value="users", key="#user.id")
void update(User user);

@CacheEvict(value="users", key="#id")
void delete(BigInteger id);

A problem may arise when, for example, getUser() is called while removeFriend() is in progress, because the user with the stale friend count would be re-cached (or would it?):

public User getUser(userId) {
    return userDao.find(userId);
}

@Transactional
public void removeFriend(userId, friendId) {
    friendDao.remove(friendId);
    user.setFriendCount(--numFriends);
    userDao.update(user);
    // do some other stuff
}

How can I ensure that this doesn’t update the cache before the database transaction has completed? Do I place @CacheEvict on service methods in addition to the DAO methods? Or, do I add read/write locking to the service methods? And if so to locking, are there any libraries to lock based on id since I would only want to lock on each user instead of locking globally, e.g. @GuardedBy("userLocks.getReadLock(#userId)")? Is there a generally accepted way of handling caching and transactions?

Many thanks!

Answer 1

I should’ve looked into EHCache documentation a bit more because the answer is here.

EHCache 2.4+ works with Spring’s @Transactional annotation. Just need to configure a transaction manager lookup.