This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
The parentProduction collection is probably empty. The problem is most likely not with the JSP. You need to debug the code in your action class that is supposed to populate the parentProduction collection and put it in some scope, such as request or session. Use System.outprintln() statements or a debugger to help you figure out what is going wrong.