Skip to main content

Chatting with the database

At APEXPosed in Brussels I attended a presentation by Lucas Jellema called "Reaching out from PL/SQL". It was all about leveraging the central position of the Oracle database in the application architecture. Of course the examples were accompanied by some fine demo's. One of them was sending and receiving email by the database: You could ask the database a question, and the database answered that one. Another one was sending instant messages from the database when some data was changed. Interesting stuff!
So I decided to combine those two: Why not chat with the database? Ask the database a question using an IM client and the database will (try to) answer to that question...

I started off with downloading and installing the Oracle-XMPP code (XMPP stands for Extensible Messaging and Presence Protocol). Because I needed my own XMPP-server, I also downloaded and installed OpenFire. One of the options when installing OpenFire is to use an Oracle Database for storing the data (using a OJDBC driver). In the OpenFire schema there is a table called ofoffline, used to store messages send to users that are offline. By defining a user (called 'oracle'), that is always offline, I can get "my" messages there. I also wrote a trigger on that table to handle the requests. And the result is someting like this:
How cool is that?
Of course you can (and should) modify the parsing of the query to make it more userfriendly - and not vulnerable to SQL-Injection. But you can chat with your database using this stuff!
3 comments

Popular posts from this blog

Showing a success message after closing a modal dialog

APEX 5 comes with Modal Dialogs out of the box. Very neat. Especially for adding and changing data. And to minimise the number of time a user has to click, it could be useful to add a "Close Dialog" process after the actual data processing. When the data processing fails, the Dialog stays on top showing the error. When data processing runs fine, the Dialog is closed ... without any confirmation. And this might be scary for a shaky user.

So how can we provide the user some feedback? On Page 4 of the Sample Dialog Application you can see one solution: up on a Dialog Closed Event on the parent page it does a redirect to refresh the parent page appending the success message of the "Close Dialog" process. This has two drawbacks. First, it probably refreshes more than necessary. And second, if you're using multiple layers of dialogs (dialogs that open other dialogs) the message appears in the "parent dialog".
As an alternative you could follow these steps: 1…

A review of APEX World 2017 - Day 1

Last week the SS Rotterdam was the beautiful location of the largest gathering of APEX Developers worldwide. With around 380 (!) attendees a new high was set. And they came from all over the world : I spotted people from The Netherlands, Belgium, Switzerland, Austria, Croatia, Germany, Denmark, Norway, UK, Ireland and the USA. And I even might have missed one or two ….

The event started with a presentation by the “father of APEX”, Mike Hichwa, talking about "Oracle APEX Past, Present and Future”. Of course everyone is curious what the APEX future might bring: Friendly URL’s, automated testing, more JSON, concurrent APEX versions, third party Oauth 2 authentication (think Facebook, Google), APEX app diff and more, a lot more, REST capabilities. And now we have to wait for APEX 5.2 … and that might take a while! 
After this keynote, the conference split up in three tracks. After the coffee break I returned to to big theatre where Geertjan Wielenga talked about "Finally Javas…

Push changed rows to an Interactive Grid

For pushing changes from the database to the end user, the regular solution is using websockets. A change in a record is detected - using a trigger or using the CQN (Change Query Notification) feature - and a notification is send to a websocket server. That websocket server broadcasts the notification over a channel to all browsers that are tuned in to that websocket channel. Then the browser reacts to that notification, usually showing an alert or refreshing a report. This trick is described on multiple sites, just Google for "oracle apex websockets" or similar.

So back in the old days, we used that notification in the browser to refresh the (interactive) report. But along comes the Interactive Grid (IG). While he full-refresh mechanism still works for IG, an IG has also the option to refresh just one row.  So wouldn't it be awesome that just the changed row(s) get refreshed upon a change in the database, instead of the whole report? Can we do it ... yes we can!
First i…