Sometimes, we wish to execute some logic just before and/or just after a method's main logic executes. For example, we might want to measure the execution time of a method to track down performance problems, or we might want to send a message to a log every time we enter and leave a method, to make it easier to track down bugs or exceptions.

The most common solution to these kinds of problems is to add a little bit of code at the beginning and end of every method, implementing the logic to profile or log in each method. This approach, however, has problems: the logic needs to be implemented several times, and; if we later wish to modify or remove the functionality, we need to modify several methods.

Aspect-oriented programming (AOP) is a programming paradigm that solves the problems mentioned earlier by providing a way to implement the logic to be executed just before and/or just after a method's main logic in a separate class. EJB...