Looking back at the history of Apache Web Services, the Handler concept can be considered as one of the most useful and interesting ideas. Due to the importance and flexibility of the handler concept, Axis2 has also introduced it into its architecture. Notably, there are some major differences in the way you deploy handlers in Axis1 and Axis2. In Axis1, adding a handler requires you to perform global configuration changes and for an end user, this process may become a little complex. In contrast, Axis2 provides an easy way to deploy handlers. Moreover, in Axis2, deploying a handler is similar to deploying a service and does not require global configuration changes.
At the design stage of Axis2, one of the key considerations was to have a mechanism to extend the core functionality without doing much. One of the main reasons behind the design decision was due to the lesson learned from supporting WS reliable messaging in Axis1. The process of supporting reliable...