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.
Portlets in Action requires that you have experience in web application development using JSPs and Servlets.
The technologies covered in the book, like Spring, Hibernate are introduced gently to the readers. So, you'll be good even if you don't know Spring/Hibernate.