This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
You can find several possible solutions to this by Googling "JSP please wait message". I've used the technique demonstrated in this link before, and found that it works pretty well. The example is written for JSF, but the technique can be used in any JSP.