What open framework for managing complex page flows?

Question

I am trying to find out what open source framework+language to use to build a webapp(a rich internet application) that has complex page flows. I have coded a lot in C++ and a little in Java. I have heard of JSF and Spring. Never used it though. I am also wondering whether Java or Python will be better suited for quicker development and implementation(considering I have limited exposure to both!)

Thank you for your time.

J