Using interceptors

Interceptors, as the name suggests, are methods that intercept other methods. With interceptors, you can write one method that will always run before one or other methods of your choice. Interceptors are useful when you are required to implement some cross-cutting concern, which should take kind of a global effect on some other scenarios. For example, suppose you want to log each method call in a payment processor bean, so you can later check what really happened during runtime in production. The direct mechanism to implement this is to write a logging function, then call it in each method in the payment processing bean. Although this seems simple, it's really redundant with the existence of interceptors. With interceptors, you can write your logging function once, and attach it with all other methods that you need to associate logging with. Interceptors...