On Thu, Nov 18, 2010 at 1:05 PM, biokys <mulle...@gmail.com> wrote:
> Hi, I am trying to find out, how to store data in a local DB and
> remotely over HTTP in one transaction. Does exist any native mechanism
> in Android phone for transactional behavior?
>
> Thx Honza
Honza,
Short answer is: I don't think so.
In order to achieve this, you would need to look at Distributed
Transaction Coordinators, if you require full transactionality.
Java EE has JTA (Java Transaction API) but it's not present on mobile
platforms. To achieve this it relies on few very crucial things:
- JDBC 2.0 drivers for each data source you need in your distributed
transaction that actually implements XADataSource and XADataConnection
- JEE Application Server
Android API mentions XADataSource and XAConnection, just have a look
at javax.sql.DataSource documentation, but there is nothing else. I am
pretty sure that SQLite does not support such mechanisms, but I could
be wrong.
You can try doing it the garage way:
db.beginTransaction();
try {
//send data to SQLite
//send data to external service
db.setTransactionSuccessful();
} catch (SQLException) {
//error in DB: contact the server to revert the commit and hope
it will do it
} catch (IOException) {
//error with the external server, and you have no guarantee,
whether it has been written or not
} finally {
db.endTransaction();
}
As you can see, you can have guarantees only about the internal SQLite
database. As soon as you involve network in your transaction, things
get orders of magnitude more complicated.
I am not sure, how strict are your requirements on transactionality.
You could also implement some timer on your server that is
transactionally persisted to a DBMS on that server, so that crash +
restart or network outage would not cause it disappear. They you would
revert any uncommitted transactions after some timeout. That gets you
somwhere, but I am pretty sure it will break in some scenarios.
--
Daniel Drozdzewski
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