In Chapter 8, Writing an Axis2 Module, we will learn that an Axis2 module can be considered as a collection of handlers. So by engaging a module either globally to a service or to an operation, handlers will be placed in the corresponding phases, depending on the phase rules. If a module is engaged globally, all the services in the system will be affected, and there is a probability of changing both global and operations flows (every operation in all the services). If a module is engaged to a service, flows belonging to all the operations in that particular service will be changed. If a module is engaged to an operation, every flow in that operation may be changed.
The only way of changing a flow is by adding a handler(s) to a phase in the flow. Therefore, module engagement will cause a change to the handler chain dynamically. A module can be engaged dynamically (at runtime) or statically (at deployment time). If you want to engage a module statically...