Whatever you are doing on line 66 of AdminManager must be refering to a null object. I can't say for sure - since I don't know what is happening on that line - but my guess is you have not assigned a value to admin. Looking though your code this does seem to be the case. You seem to have a variable called cadmin which you use to refer to a Statement instance. I don't see anywhere that you do the same for your variable admin.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com