Getting events from a database

Using Oracle you can setup a Trigger on a table and then have the trigger send a JMS message. Oracle has two different JMS implementations. You can then have a process that will 'listen' for the message using the JDBC Driver. I have used this method to push changes out to my application vs. polling.If you are using a Java database (H2) you have additional options. In my current application (SIEM) I have triggers in H2 that publish change events using JMX.

Don't mix up the database (which contains the data), and events on that data.

Triggers are one way, but normally you will have a persistence layer in your application. This layer can choose to fire off events when certain things happen - say to a JMS topic.

Triggers are a last ditch thing, as you're operating on relational items then, rather than "events" on the data. (For example, an "update", could in reality map to a "company changed legal name" event) If you rely on the db, you'll have to map the inserts & updates back to real life events.... which you already knew about!

You can then layer other stuff on top of these notifications - like event stream processing - to find events that others are interested in.

James

Hmm. So you're using PostgreSQL and you want to "listen" for events and be "notified" when they occur?

http://www.postgresql.org/docs/8.3/static/sql-listen.htmlhttp://www.postgresql.org/docs/8.3/static/sql-notify.html

Hope this helps!