WebFrame:An Extensible Multi-layer Web Application Server

Web application servers (WASs) are middleware platforms for deployment and execution of component-based web applications. To cater for an increasingly diverse range of QoS demands, WAS must be capable of adaptation during execution to modify itself and to respond to changing conditions in its external environment. To accommodate such changes, WAS should provide both deployment-time configurability and run-time reconfigurability. Unfortunately, most of the mainstream web application servers adopt a monolithic architecture and “black box” philosophy to their design, and fail to properly address such requirements. In our point of view, reconfigurability of WASs should be available at any time of the whole lifecycle. In this paper, an extensible multi-layer model that supports multi-phase extension using computational reflection, microkernel, and component techniques is proposed for web application servers. The model is structured into four layers. Both deployment-time configuration and run-time reconfiguration at multiple layers is supported in this model. The model is applied in the design and implementation of a WAS, referred to as WebFrame. The comparative evaluation of the performance impact of reflection and multi-phase extension on systems are given. The experiments show that WebFrame takes on good performance.