In our security check example in @SecurityCheck section, the objects of ClassA, ClassB, and ClassC are the target objects of the SecurityChecker aspect or are referred to as advised objects. In Spring AOP, the framework will create proxy objects for these objects in runtime to fulfill the SecurityChecker aspect contract. By default, Spring AOP uses standard JDK dynamic proxies to create AOP proxies. The JDK dynamic proxy can only proxy by an interface. If a target class doesn't implement an interface, Spring AOP will use CGLIB (https://github.com/cglib/cglib) to create a proxy by subclassing the target class. In our security check example, Spring AOP will create proxy objects using CGLIB.