I have set of java objects and I use castor to convert them into xml string, now I need to convert those xml string into PDF file on the fly for easy view and printing. I could use FOP or iText, I am not sure which one is better. (performance? easy API, etc), is there any others free API doing the same job?
iText has the feel of a normal Java API, while FOP uses XSLT which has a different programming model. That can take a little time to get used to. You'd also have to know XSL-FO, although if your layout is simple then you can probably copy/paste from examples.