The development process for creating J2EE web applications is complex and tedious, and is thus error prone. The quality of a J2EE web application depends on correctness of code as well as the efficiency and flexibility of its architecture. Although the J2EE specification has promisedto hide the distributed nature of the application, application developers still have to be aware ofthis fact in both the design (architecture) and implementation (code) perspectives. In this thesis,we present the detailed design of our pattern-based J2EE development tool, RoadMapAssembler(RMA). RMA demonstrates how patterns can be used to generate efficient architectural code whilealso hiding the deployment logic and distributed nature of J2EE applications in the implementationperspective. Furthermore, it shows the generation of a J2EE framework as a process of assemblingpatterns in an incremental fashion using known inter-pattern relationships.