Looks like you need to synchronize local databases rather than
DataContexts (which would be a secondary concern in this situation).
Synchronzing contexts (the default implementation at least) only
works if all of them are connected to the same database. I.e. if DC1
in APP1 commits its changes and DC2 in APP2 receives an event for
this commit, DC2 will refresh its objects, but will not mark them as
dirty (as it assumes that they are already committed), so even if you
commit DC2 after the event is processed, it won't save anything to
the DB.
You will need to investigate what clustering options exist for the DB
that you are using. IIRC there was a JavaGroups based solution for
HSQLDB.
Andrus
On Nov 13, 2006, at 1:32 PM, Andreas Hjortsberg wrote:
Hello and thank you all for your replies.
Yes, you are correct Andrus, my intentions are to use an ordinary
dataContext, and the reason is that my application must be able to
work offline.
I looked through the code regarding JavaGroupBridge and it seems to
me that it is a quite straight forwarard to
get two or more applications to talk to each other over a local
network, and the different datacontext will be updated etc..
The more diffucult thing to implement will be to add some logic to
commit the changes on the remote dataContexts to
their local databases.
In the perfect world I don't need to care about it, because the
remote context will be updated, and next time someone commit the
changes on their
datacontext the local database will update on a correct manner, but
if a user refresh the data before it comes comitted I
will lose the changes to this datacontext.
Now to my question; where should any of you add this logic? One
could make sure that the client application always commits changes
before he does
anything. It does not feel like a good solution, though. Another
approch would be to add another static datacontext for the
application, which will commit after any event has been received
through the JavaGroupBridge?
Regards
/Andreas
As Ari just mentioned, JGroups site is located here:
http://www.jgroups.org
Cayenne has built in support for using JGroups as a provider for
cache synchronization. You can configure it in the Modeler:
* Check "Remote Change Notifications" for the DataDomain
* Click the "Configure" button next to it and enter the settings that
you need (or leave the defaults).
And of course you can use JavaGroupsBridge for your own custom
messaging if you need functionality beyond just cache
synchronization.
Andrus
On Nov 11, 2006, at 9:15 AM, Andreas Hjortsberg wrote:
Hello,
In the api docs for
JGROUPS_CONFIG_URL_PROPERTY
http://incubator.apache.org/cayenne/2_0/api/cayenne/index.html
there is an invalid link for an example file. I think it's Filip's
son who shows up, very cute though.
http://www.filip.net/javagroups/javagroups-protocol.xml
Is there anyone who knows where I can find another example?
I'm about to start a project where all clients will have a local
swing application and database, probably derby or hsqldb.
It is very important what then a client change some of his objects
it is broad casted over the local subnet and the other clients will
be updated and it also notifies a main server.
Has anyone used cayenne and jgroups for this? Is it the path to
take? I have looked around but have not found any example or
comments on this. Or is the existing integration between jgroups
and cayenne designed to mainly work between instances on a web
application?
Regards
/Andreas
