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The ability to dynamically change the behavior of an application is becoming an important issue in contemporary rich client software development. Not only can programmers benefit from dynamic updates during the development of concurrent applications where recreation of complex application states can be avoided during test and debugging but also at post‐deployment time where applications can be updated transparently without going through the well‐known halt, redeploy and restart scheme. In this paper, we explain how our dynamic update framework achieves transparent dynamic updates of running Java applications while guaranteeing both type and thread safety. A novel feature of our approach is that it supports full redefinition of classes by allowing changes to the type hierarchy. Our approach is based on a lightweight runtime system, which is injected into an application via bytecode transformations at class loading. We show how our approach can add dynamic update capabilities to rich client development by integrating it with the NetBeans rich client platform. Performance experiments on our NetBeans implementation show that the overhead of our approach is low when applied to component application programming interface classes. To the best of our knowledge no other existing approach achieves the same level of low overhead and programming transparency. Copyright © 2009 John Wiley & Sons, Ltd.

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The development of a dynamic software updating system for statically-typed object-oriented programming languages has turned out to be a challenging task. Despite the fact that the present state of the art in dynamic updating systems, like JRebel, Dynamic Code Evolution VM, JVolve and Javeleon, all provide very transparent and flexible technical solutions to dynamic updating, case studies have shown that designing dynamically updatable applications still remains a challenging task. This challenge has its roots in a number of run-time phenomena that are inherent to dynamic updating of applications written in statically-typed object-oriented programming languages. In this paper, we present our experience from developing dynamically updatable applications using a state-of-the-art dynamic updating system for Java. We believe that the findings presented in this paper provide an important step towards a better understanding of the implications of dynamic updating on the application design.

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