Hi Roland,
Are you using an O/R mapper like Hibernate or JDO to do your persistence
or pure JDBC code?
You could embed one of the OSS DB's like Apache Derby or HSQL?
Your app could then start up with different SessionFactory
configurations depending offline or online mode...
Minimal code changes would be my guess...
My initial thoughts would be that every record in every table would have
to have a sync flag of sorts ( to indicate it has been synced with the
master database ).
You could then use Hibernate Event Handlers to set the sync flag to
offline on all persisted objects without having to impact to greatly on
your existing code.
When your application is then switched to online mode, just do a quick
run through all tables in the local DB where the objects have an offline
flag and persist those to your master online DB?
And reset the flag in your local DB? Could also include revision numbers
if you wanna get really funky...
That way you could then give the user the ability to resolve conflicts
between his offline data which he may have changed and online data that
someone else may have changed there?
Hope it helps...
Cheers,
Renier
Roland Giesler wrote:
I looking for some advice regarding using a disconnected java application
running on Postgres.
Scenario: A Java web application read/writes a PG database in a
transactional environment. To be more specific, status information about
clients is looked up from some table(s), and a number of lines are then
entered into an order. The items that can be ordered are in another table,
which must also be available offline. Lastly the completed order must of
course also be available offline, for submission later when an internet
connection is available again.
Now this application should be able to work when disconnected from the
server. Of course the application can be written to create offline copies
of the data in a local file, but basically that would cause some problems,
since it would involve a lot of coding firstly, but also mean that different
code would be required for online and offline operation.
My question is, is there any technology that would allow this type of
funtionality with Postgres, like some type of caching enjine, or something
else, acting as a sort of mini "middleware" of sorts (to borrow that term)
to do this for me.
Thanks
Roland Giesler
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