Hey Dustin,
Module sounds very interesting.
Indeed I don't think there is a clean way to get at the transaction object.
I don't see a problem with adding it as a property on TransactionEvent.
We'd probably have to add it to TransactionRequest as well in order to pass
it into the handlers that issue TransactionEvent. Again I don't see a big
problem with that.
Anyways else have any thoughts on this on?
-Justin
On Thu, Sep 5, 2013 at 4:56 PM, Dustin Parker <[email protected]>wrote:
> Hi list,
>
> I'm working on adding a community module to GeoServer (with an eye towards
> making an extension) that does notifications based on WFS activity. The
> plugin has some things that tailor it towards our use case, so I'm working
> on making it more generally usable.
>
> One snag I've hit so far in preparation is the management of GeoTools
> Transactions during a WFS Transaction (this is going to be confusing, I can
> tell). The GeoTools Transaction ultimately controls what database
> transaction is used for database queries, so if two consecutive
> Insert/Update/Delete elements execute against the same database, GeoServer
> makes sure they also execute in the same transaction.
>
> The notification plugin notifies on tables related to the one being
> altered based on some extra configuration data (nothing is published by
> default). In other words, if view Y depends on table X, altering table X
> can cause notifications to be sent out about features in view Y. To find
> those related features, the notification plugin (or an intermediary like
> App Schema) must issue further queries. If nothing else is done, those
> secondary queries are in the AUTO_COMMIT transaction, so they don't see the
> changes that were just made to X. In the past, we did some questionable
> things that enforced one transaction per data store, but that approach no
> longer works.
>
> What I've done this time around, as a TransactionListener, is grab the
> current transaction from any FeatureCollection that happens to be or is
> backed by ContentFeatureCollection. This entails mild use of Reflection to
> get at some protected/private fields. Whenever the notification plugin goes
> to make a secondary query, it applies the Transaction it got from the
> incoming FeatureCollections. I'd rather not do this, however, as I believe
> it's a brittle approach; FeatureCollection and FeatureSource can be wrapped
> by any manner of wrapper objects, so it's impossible to really know what
> the "real" object is, and since I'm using private/protected fields, this
> code can break at any time. You can see the gory details here:
>
> https://github.com/**dustinparker/geoserver-**
> notification/blob/master/src/**main/java/com/fsi/geoserver/**
> wfs/TransactionCache.java<https://github.com/dustinparker/geoserver-notification/blob/master/src/main/java/com/fsi/geoserver/wfs/TransactionCache.java>
>
> Is there some legitimate way that the TransactionListener can get at the
> org.geotools.data.Transaction created by
> org.geoserver.wfs.Transaction.**execute()?
> If there's no current way to do it, I think TransactionEvent makes the most
> sense.
>
>
> --
> Dustin Parker - Forward Slope, Inc.
> Cell: 619 277 2591
>
> SYBWB UI EXCEFI EK BEIF IRXMSURK SR BTBWF YMHEK
> OWRZXBH--KBES, OXEMIUZXB, EKD CWRKV. - Y. X. HBKNABK
>
> H4sIAOlx7FACA02MuQ7CMBQEe3/**FdjTgcIWrSUMBFQVI1A5+2BaJ
> HcUPTP6eU4J2dmb37o49K0MR4Yw1lV**djnDdiJHGwinFSvsewqmnI
> SzH+Uh0o/jiCR92hVifrPEkx+**VrRhmul//upxNF27xz8Uj5DIXKJ
> ne1ji0jPg5nEJiRopz8W3ahFCu2lEH**OJePMoK1WTWDwrT9CqQyIk
> V1VIrWMCU+**QoBrDMzSrLShWtDK3JimU+**zBcj8QDNJmEc9gAAAA==
>
>
>
>
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--
Justin Deoliveira
OpenGeo - http://opengeo.org
Enterprise support for open source geospatial.
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