Efficient runtime metaprogramming services for Java

Abstract

The Java programming language and platform provide many optimizations to execute statically typed code efficiently. Although Java has gradually incorporated more dynamic features across its versions, it does not provide several metaprogramming features supported by most dynamic languages, such as structural intercession (the ability to dynamically modify the structure of classes) and dynamic code generation. Therefore, we propose a method to add those metaprogramming features to Java in order to increase its runtime adaptiveness, while taking advantage of the robustness of its static type system and the performance of its virtual machine. We support the dynamic addition, deletion and replacement of class methods and fields, and dynamic code generation. The metaprogramming services are provided as a library, so neither the Java language nor its virtual machine are modified. We evaluate our system, called JMPLib, and compare it with the existing metaprogramming systems for the Java platform and other highly optimized dynamic languages. JMPLib obtains similar runtime performance to the existing fastest system that modifies the implementation of the Java virtual machine. Moreover, our system introduces no performance penalty when metaprogramming is not used, and consumes fewer memory resources than the rest of implementations for the Java platform.