Spring in action, but the truth is that you learn spring by using it; In fact you can learn all the frameworks by doing a quick start tutorial and then building on top of it; Also Spring Recipes is a good book by Apress, But BEWARE! you keep on doing those examples that explain things in public static void main( ), you would be "hack" framework learner and not the real deal; I often find it useful to do say 25 such examples and then create a typical CRUD application (say a phonebook), where I setup everything and do the entire thing; that way I have: A.) Full control B.) Will learn more because of the setup. C.) Learn things that are not mentioned in books, like quirks etc.
Off course my advantage is that I use spring mvc and webflow for my work, that helps a bit ;). Any framework I wanna learn, I typically check out the source code from svn or git or whatever and sift through code class hierarchy to see javadoc and understand the flow to figure out a framework, Although Spring is pretty vast and it'd take loads of extra time ... I recommend the same technique in some of the cases, this is prolly cuz there are frameworks out there that are not well documented, (take for example Plexus Container on which Maven depends); you'd have an easy time later on figuring out whats happening behind the scenes, plus I think aside from Apache Wicket (a web framework), Spring team is the only team I have seen that writes such good quality code ... I like their documentation etc. very useful.
Good luck dude!
Addendum: With respect to documentation, an example is Hibernate, Oh mah god! their source is NEVER documented, I won't name developers, but some of the source methods are written as if they are SQL statements hahah!
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