Advantages of using interfaces in Spring AOP

Question

I read this on a guideline

"When using Spring AOP always use interfaces so normal AOP proxying can be used (rather than CGLIB)"

What could than mean? I have very good idea on AOP and have implemented AOP myself before. But completely out of clue.

Answer 1

Simply said there are 2 way for proxying an object :

• dynamic : you create a new object that implement the same interface than the target object and encapsulate this last in addition with the proxy logic

• static : when you compile the target class you add the aspect logic directly into the compiled class (cglib way)

Dynamic proxy can only apply on object that implement an interface and will be used only if you reference the instance using the interface (which is advised here) whereas static proxy can apply on everything

Following the spring guideline will allow you to use any of the method (you can simply switch using spring configuation) instead of being coupled to cglib.

Note than static proxy allow proxy logic to be applied even when you call a proxied method from another method inside the same class whereas with dynamic proxy the call must come from outside.