I want to write a java extension to execute a query (with oracle index optimizer hint) en return the result in a record list. But my problem is that I can't find any API or other documentation of how I am able to query and how to set the result into a record list. 
Can anyone help me please?

Hello Hans,

Integration Studio doesn't offer much in terms of public API's for extension code to access OutSystems Platform functionality.

For accessing the Main Platform Database and configured Database Connections, you can use the API which is depicted here with the care that it is *not* a supported API.

You can then use the returned objects to access the database API's which use a model similar to ADO.NET .

The examples provided in the mentioned post should provide you with a first example on how to execute the queries and obtain information.

Best regards,
Ricardo Silva
Thank you for your reply Ricardo. 
Perhaps I'll try to use the API later-on, but for now I skip it.

i want to use currency converter api. 
I have search some API  but dont know how to call or take refrence of API in outsystems.
Can anyone help me pls?