In Axis2, there are many ways to extend the functionalities. In this book, we will be discussing a few of them, which are listed here:
Service extension of the module
Custom deployers
Message receivers
Both Axis1 and Axis2 have the concept of handlers. But when compared to Axis 1.x, there are few changes in the way Axis2 specifies and deploys handlers. In Axis 1.x, if you want to add a handler, then you need to change the global configuration file and then restart the system. In the meantime, it does not have a way to add or change handlers dynamically.
To overcome this problem as well as to add new features, Axis2 introduced the concept of web service extensions or a module where the main purpose of a module is to extend the core functionality. It is similar to adding handler chains in Axis1.x. The advantage of the Axis2 module over the Axis 1.x handler chain is that you can add new modules without changing any global configuration files...