We have all been frustrated by difficult to maintain code. Some code is difficult to maintain because it does too much - e.g. handling transactions, persistence and security, as well as implementing business rules. Changing that kind of code requires you to understand and tackle many different concerns. Other code might be difficult to maintain because the implementation of a particular feature (e.g. audit logging) is scattered throughout the code base. Changing the implementation of that kind of feature involves changing many components. This talk describes how to improve the maintainability of enterprise Java applications by using dependency injection, and Aspect Oriented Programming. We will show how you can implement business logic using POJOs that are decoupled from infrastructure concerns such as persistence, security and transaction management. We will also describe how to modularize concerns such as audit logging that are normally implemented by code that is mixed in with the business logic. The presentation has numerous Spring and AspectJ examples.

You can download the slides from here: presentation (pdf) and the source code examples from here.