Alex Rivera | Logout

Getting events from a database

Asked 2009-05-01T16:58:05.297
33

I am not very familiar with databases and what they offer outside of the CRUD operations.

My research has led me to triggers. Basically it looks like triggers offer this type of functionality:

(from Wikipedia)

There are typically three triggering events that cause triggers to "fire":

  • INSERT event (as a new record is being inserted into the database).
  • UPDATE event (as a record is being changed).
  • DELETE event (as a record is being deleted).

My question is: is there some way I can be notified in Java (preferably including the data that changed) by the database when a record is Updated/Deleted/Inserted using some sort of trigger semantics?

What might be some alternate solutions to this problem? How can I listen to database events?

The main reason I want to do this is a scenario like this:

I have 5 client applications all in different processes/existing across different PCs. They all share a common database (Postgres in this case).

Lets say one client changes a record in the DB that all 5 of the clients are "interested" in. I am trying to think of ways for the clients to be "notified" of the change (preferably with the affected data attached) instead of them querying for the data at some interval.

java database database-design events triggers
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1 Answer

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I would suggest using a timestamp column, last updated, together with possibly the user updating the record, and then let the clients check their local record timestamp against that of the persisted record.

The added complexity of adding a callback/trigger functionality is just not worth it in my opinion, unless supported by the database backend and the client library used, like for instance the notification services offered for SQL Server 2005 used together with ADO.NET.

answered 2009-05-08T21:04:59.943

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