Hi Valeriu,
Generally, all you need is possible.
* I need a custom jsp to be executed on some event - is it possible?Custom code is executed once an interaction is accepted (answered) by an agent by default. It's possible to execute custom operation even on other desktop-related events like EventRinging but it makes customization as bit complex
* I need this jsp to connect to a Oracle database and query some data - is this possible, as well?Yes, it's possible but you would need to copy Oracle JDBC drivers to GAD's Tomcat instance.
last but not least I need to pop-up a new window with a custom URL?Yes, possible
I would recommend you reading the Genesys Desktop 7.6 Developer’s Guide at first. You can find there useful information and customization examples as well.
R.