I recently just finished up a couple of web application projects were I used Gentle.NET and db4o. Since I haven't blogged for awhile, I guess these topics will make good cannon fodder, right?
There are two immediate down-sides to using db4o: setting it up, and the GPL license. Since I was doing a web app the license didn't matter too much since its GPL 2, although if they upgrade to GPL 3 I'd have to start migrating some of these sites away. Fortunately most of them are "one-shots" -- I won't have to touch them again, nor will any one else, once deployed.
Setting it up is a one-time thing per project, but doing it is kind of a pain in the ass--you have to wander around your application, look for a good entry-point / exit point to setup the database and configurate it (configuration TO THE MAX ! ! !).
After that, though, db4o is just kind of seamless -- you just... use it. Of course, that's not without its few, niggling problems, like everything being an impilict transaction. This means that there's no way to start a "seperate" transaction. The codebase using db4o is littered with the following two lines of code, no variation:
It is really, really annoying. Since transactions are impicit this is absolutely necessary to avoid data-loss; and, of course, when I really *NEED* to use a transaction, I need to make sure everything's been committed to the database first, beforehand, so I don't rollback a ton of objects by mistake.
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