JavaCloak - considering the limitations of proxies for facilitating Java runtime specialisation

Abstract

This paper discusses issues pertaining to mechanisms which can be used to change the behaviour of Java classes at runtime. The proxy mechanism will be compared to and contrasted with other standard approaches to this problem. Some of the problems the proxy mechanism is subject to will be expanded upon. The question of whether statically developed proxies are a viable alternative to bytecode rewriting was investigated by means of the JavaCloak system, which uses statically-generated proxies to alter the run-time behaviour of externally-developed code. The issues addressed in this paper include ensuring type safety, dealing with the self problem, object encapsulation, and issues of object identity and equality. Some performance figures are provided which demonstrate the load the JavaCloak proxy mechanism places on the system.