How to update non-jars?

Question

Hello,
In my JWS app I save on the user system a db.sqlwrapper database, for the app consumption (not read-only). I now need to make a change to the schema, of the db.
Is it possible that users on their next update (launch of the app) they once only execute java code that would do the required (perhaps in some extra .jar) and then not again (since the change needs to be done only once)?

Answer 1

Easiest way would be to provide a db upgrade mechanism. I'd suggest numbering your upgrades and creating a table where you store executed upgrades. On application startup (or db startup if they differ), you'll just need to check the presence of upgrades higher than the last executed one.
I've been doing this for a long while.
In my case it's even easier 'cause I've got both a read-only db and a user one.
I record upgrades by number and key (actually keys comma separated) in the read-only db (that gets updated through JWS), storing SQL instructions in a property file (I read using the key retrieved in the DB).
That's it: select max(required upgrade) as A from readOnly.UP, select max(executed update) as B from userDB.UP, if A>B for each key K in readOnly.UP where K>B, split K, for each part of K read property and add text as batch, once done cicling through K.parts execute batch and insert new line in userDB.UP.
One last thing: at the end of userDB creation you should insert a line in the userDB.UP to mark out your DB version.
This way you'd be able to upgrade your db schema (and data if needed) whenever you like.
Bye.