I don't claim to know anything about this, but our barcode readers connect to the PCs and when you scan something the equivalent test appears in the currently open application. For example, if I open Notepad and scan a barcode, the text representation of the barcode appears in notepad as if I typed it on my keyboard.
I'm guessing the answer to your question really depends on how your scanners work and what you want to do with the output. If you want the result to appear in a text item on a form and you use scanners like ours then you won't have to do anything. If not, who knows
1) You can buy barcode fonts to represent strings as barcodes. These are only available for 1 dimentionl barcodes.
2) You can buy/download code to produce 1D an 2D barcodes. We use some java code from ID Automation (http://www.idautomation.com/) to do our 2D barcodes in a web application. There are some free 1D barcode downloads on the net, but when we looked around we couldn' find free 2D barcode software. I believe they sell the barcode fonts also.
Don't ask me how the java guys use this stuff. I just know they do.
You can use beans in Oracle forms so you should be able to use this stuff I guess