title: Internals of Spring Framework and other IoC containers
body: <p>I've been using spring for some time, but I always wondered how does it work, more specifically, how do they load and weave beans/classes marked only with an interface or <em>@annotation</em>. </p>
  
  <p>For the xml declarations, it's easy to see how spring preprocesses my beans (they are declared in the xml context that spring reads), but for the classes marked only with annotations, I can't see how that works, since I don't pass any agent to the jvm or so.</p>
  
  <p>I believe there is some Java/JVM hook that allows you to preprocess classes by some sort of criteria, but I wasn't able to found out anything on the docs.</p>
  
  <p>Can someone point me to some docs? Is this related to the <em>java.lang.instrument.ClassFileTransformer</em> API?</p>