This book is about what you need to know to start using Hibernate, Spring, Flex and
Maven together, whether you are a Java developer or a Flex developer.
You need some Java basic even if I dedicate a chapter to the
IDE configuration to allow beginners to configure all what they need to develop
JEE applications.
It is definitely not an Handbook for Flex.
Have a look to this post
https://coderanch.com/t/495119/Flex/Beginning-Java-Flex