Dynamic Aspect-oriented Programming Research Articles

Efficient runtime aspect weaving for Java applications

ContextThe aspect-oriented paradigm is aimed at solving the code scattering and tangling problem, providing new mechanisms to support better separation of concerns. For specific scenarios where high runtime adaptability is an important requirement, dynamic Aspect-Oriented Programming (AOP) represents a useful tool. With dynamic AOP, components and aspects can be woven and unwoven at runtime, enabling applications greater responsiveness when dealing with different or changing requirements. However, this responsiveness typically incurs a cost in terms of runtime performance and memory consumption. ObjectiveBuild an efficient dynamic aspect weaver for Java that provides the best runtime performance compared to the existing approaches, minimum memory overhead consumption, and similar functionalities to the widespread runtime weavers. MethodWe design and implement weaveJ, a dynamic aspect weaver for Java. This dynamic weaver leverages the invokedynamic opcode introduced in Java 7, which allows dynamic relinkage of method and field access. We compare the functionalities of weaveJ with the existing dynamic weavers for Java, and evaluate their runtime performance and memory consumption. ResultsweaveJ shows the best runtime performance for all benchmarks and real applications executed. Method interception with invokedynamic is at least 142% faster than the techniques used by the existing runtime weavers. The average cost of dynamic weaving using invokedynamic is only 2.2% for short running programs, and 1.5% for long running applications. Moreover, the use of aspects in weaveJ does not imply additional memory consumption. ConclusionThe dynamic aspect weaver implemented demonstrates that invokedynamic is a suitable mechanism to provide efficient runtime aspect weaving for Java applications. Moreover, it supports concurrent and programmatic aspect (un)weaving at any point of execution, a wide set of join points, class and object weaving, and allow aspects to have their own state. Neither the Java language nor the virtual machine needs to be modified.

Damon: A distributed AOP middleware for large-scale scenarios

Context The development of distributed applications in large-scale environments has always been a complex task. In order to guarantee non-functional properties like scalability or availability, developers are usually faced with the same problems over and over again. These problems can be separated in distributed concerns, as for example, distribution, load-balancing or replication, just to name a few. Nevertheless, none of the current solutions in adaptive middleware area, like Aspect-Oriented Programming (AOP), is capable of implementing these distributed concerns transparently. Objective In this article, we present a distributed AOP middleware for large-scale development, called Damon. Its main goal is to implement true distributed aspects, which enables the use of distributed concerns in applications that were not specifically designed for distributed or large-scale scenarios. Method Our middleware comprises two main layers: a distributed composition model and a scalable deployment platform. The distributed composition model envisages separation of distributed aspects, taking the necessary features from component models, like distribution facilities and connectors, and from computational reflection, like introspection and meta-levels. This recursive and fully distributed model provides its own Architecture Description Language (ADL), and thus allows low dependency and high cohesion among distributed aspects. Additionally, our model is built on top of a deployment platform where distributed aspects are disseminated and activated in individual or grouped hosts. This platform benefits from peer-to-peer and dynamic AOP substrates to implement its services in a decentralized, decoupled, and efficient way. Results Therefore, our middleware solution reduces the complexity of distributed application development, managing separated functionalities, and enabling necessary services like transparent reconfiguration and deployment at runtime. Finally, we have implemented a functional prototype and we conducted several experiments using the PlanetLab testbed. Conclusion Our distributed AOP approach fulfills the large-scale scenarios requirements, and represents a solid building block for future distributed transparent infrastructures.

Safe and atomic run-time code evolution for Java and its application to dynamic AOP

Dynamic updates to running programs improve development productivity and reduce downtime of long-running applications. This feature is however severely limited in current virtual machines for object-oriented languages. In particular, changes to classes often apply only to methods invoked after a class change, but not to active methods on the call stack of threads. Additionally, adding and removing methods as well as fields is often not supported. We present a novel programming model for safe and atomic code updates of Java programs that also updates methods that are currently executed. We introduce safe update regions and pause threads only there before an update. We automatically convert the stack frames to suit the new versions of the methods. Our implementation is based on a production-quality Java virtual machine. Additionally, we present SafeWeave, a dynamic aspect-oriented programming system that exposes the atomic code updates through a high-level programming model. AspectJ advice can be added to and removed from a running application.Changes are atomic and correctness is guaranteed even though weaving happens in parallel to program execution, and the system fully supports the dynamic class loading of Java. We show that the enhanced evolution features do not incur any performance penalty before and after version changes.

Component interaction behavior monitor based on dynamic aspect-oriented programming

In an open and dynamic network environment,the distributed software system demonstrates the characteristics of large scale,loose aggregation,complicated behaviors and so on.In order to monitor the interactive behaviors effectively,the monitor model based on dynamic Aspect-Oriented Programming(AOP) was proposed,by which the monitor can be more flexible,looseand transparent.With dynamic weaving mechanism,the monitor could be added or deleted in the running process of the object system to improve the dynamic character of monitoring,and based on which the implementation of the monitor was realized.The monitor was applied in the distributed e-commerce application system,and the results show that the monitor is feasible.

Optimizing dynamic dispatch with fine-grained state tracking

Dynamic mixin is a construct available in Ruby and other dynamic languages. It can be used as a base to implement a range of programming paradigms, such as dynamic aspect-oriented programming and context-oriented programming. However, the performance characteristics of current implementation of dynamic mixin in Ruby leaves much to be desired under condition of frequent dynamic mixin operations, global method cache and inline cache misses incur significant overhead. In this work we implemented fine-grained state tracking for CRuby 1. and were able to improve performance by more than six times on the microbenchmark exercising extreme case flowing 4 times to global method cache clearing, 28% to fine-grained state tracking and further 12% to inline cache miss elimination by caching alternating states. We demonstrated a small application using dynamic mixins that gets 48% improvement in performance from our techniques. We also implemented in C a more general delegation object models and proposed an algorithm of thread-local caching, which allows to reduce inline cache misses while permitting thread-local delegation changes.

Applications of enhanced dynamic code evolution for Java in GUI development and dynamic aspect-oriented programming

While dynamic code evolution in object-oriented systems is an important feature supported by dynamic languages, there is currently only limited support for dynamic code evolution in high-performance, state-of-the-art runtime systems for statically typed languages, such as the Java Virtual Machine. In this tool demonstration, we present the Dynamic Code Evolution VM, which is based on a recent version of Oracle's state-of-the-art Java HotSpot(TM) VM and allows unlimited changes to loaded classes at runtime. Based on the Dynamic Code Evolution VM, we developed an enhanced version of the Mantisse GUI builder (which is part of the NetBeans IDE) that allows adding GUI components without restarting the application under development. Furthermore, we redesigned the dynamic AOP framework HotWave to take advantage of the enhanced dynamic code evolution capabilities. The new version, HotWave2, now supports most AspectJ constructs, including around() advice and static cross-cutting. We will demonstrate both the enhanced Mantisse GUI builder as well as HotWave2, weaving several aspects for dynamic analysis in sizable applications at runtime.

Advanced runtime adaptation for Java

Dynamic aspect-oriented programming (AOP) enables runtime adaptation of aspects, which is important for building sophisticated, aspect-based software engineering tools, such as adaptive profilers or debuggers that dynamically modify instrumentation code in response to user interactions. Today, many AOP frameworks for Java, notably AspectJ, focus on aspect weaving at compile-time or at load-time, and offer only limited support for aspect adaptation and reweaving at runtime. In this paper, we introduce HotWave, an AOP framework based on AspectJ for standard Java Virtual Machines (JVMs). HotWave supports dynamic (re)weaving of previously loaded classes, and it ensures that all classes loaded in a JVM can be (re)woven, including the classes of the standard Java class library. HotWave features a novel mechanism for inter-advice communication, enabling efficient data passing between advices that are woven into the same method. We explain HotWave's programming model and discuss our implementation techniques. As case study, we present an adaptive, aspect-based profiler that leverages HotWave's distinguishing features.

Design and implementation of DBC based on dynamic AOP

Traditional approach of design by contract, due to mixing the contract code with application code, is difficult for the extensibility and reusability of software system. This paper presents a framework named JADBC for design by contract based on Aspect-Oriented Programming (AOP) to resolve these problems. By providing a new modularized element, aspect, the framework successfully separates the contracts in design by contract, from functional codes. The implementation of this framework is based on dynamic AOP which can have the contract changed at runtime, consequently, enhancing program flexibility. JADBC framework modularizes the contracts in a clear-cut fashion that is easier to design, implement, and maintain.

Aspect-oriented Programming for Dynamic Web Service Selection, Integration and Management

In service-oriented computing, applications are often created by integrating third-party Web Services. Current integration approaches, however, require client applications to hardcode references to specific Web Services, thereby affecting adaptability and robustness. Moreover, support for client-side management is rarely provided. To enable the development of more flexible and robust applications, we propose to insert a new layer between the client applications and the Web Services: the Web Services Management Layer (WSML). This layer decouples Web Services from client applications and enables hot-swapping between semantically equivalent Web Services based on availability. This mechanism allows for dynamic switching between Web Services based on selection policies that encapsulate changing business requirements. In addition, with WSML, client-side management concerns (e.g., caching, billing and logging) can be decoupled from the applications. In this paper, we identify a list of requirements for WSML to realize dynamic integration and client-side service management, and provide support for service criteria to govern the selection, integration and composition of Web Services. We also show that dynamic Aspect-Oriented Programming (AOP) is well suited to implement the core functionality of WSML.

Reflective Designs — An Overview

We render runtime system adaptations by design-level concepts such that running systems can be adapted and examined at a higher level of abstraction. The overall idea is to express design decisions as applications of design operators to be carried out at runtime. Design operators can implement design patterns for use at runtime. Applications of design operators are made explicit as design elements in the running system such that they can be traced, reconfigured, and made undone.Our approach enables Reflective Designs: on one side, design operators employ reflection to perform runtime adaptations; on the other side, design elements provide an additional reflection protocol to examine and configure performed adaptations. Our approach helps understanding the development and the maintenance of the class of software systems that cannot tolerate downtime or frequent shutdown-revise-startup cycles.We have accumulated a class library for programming with Reflective Designs in Squeak/Smalltalk. This library employs reflection and dynamic aspect-oriented programming. We have also implemented tool support for navigating in a system that is adapted continuously at runtime.Note: This extended abstract summarises our full paper [Hirschfeld, R. and R. Lämmel, Reflective Designs, IEE Proceedings Software (2004), Special Issue on Reusable Software Libraries. To appear. Available at http://homepages.cwi.nl/~ralf/rd/].

Eventizing applications in an adaptive middleware platform

An architecture supporting dynamic aspect-oriented programming establishes an event infrastructure for to extend existing application's behavior at runtime. The adaptive middleware platform described to support the eventizing applications with extensions that are added at runtime in response to new requirements or necessary adaptations. We are currently completing its implementation and exploring more advanced forms of adaptation, including dynamic changes to the event management system itself. Furthermore, the implementation is still too heavy to run on resource-constrained devices like iPAQs, so we plan to take advantage of lighter virtual machines.

Improving the efficiency of adaptive middleware based on dynamic AOP

Aspect-Oriented Programming (AOP) is used to express modular and orthogonal functionality in software components. The orthogonal functionality is programmed into an aspect, join points are used to describe where in the code the aspect should be inserted. Then the aspect is woven into the original program. Unlike compile time based strategies, dynamic AOP allows aspects to be woven at runtime. This has been shown to be very useful to adapt applications without interrupting service in a wide range of settings (business applications, wireless networks, robotics, etc.), thereby making dynamic AOP a prime candidate for supporting advanced, adaptive middleware platforms. A potential drawback of dynamic AOP is the performance overhead. In this paper, we tackle the performance problem by proposing a mechanism to implement dynamic AOP through method code replacement at runtime. The idea is to use the join points not to trigger the execution of the aspect (or advice) as it is done in most systems but to trigger the recompilation of the original code. The recompiled code contains the advice already woven into it or the callbacks to the corresponding advice, thereby greatly increasing the efficiency of the dynamic AOP process. In the paper we describe the technique, discuss extensive benchmarks to evaluate the performance gain of this approach, and compare the resulting system to other dynamic AOP approaches.

Partial behavioral reflection

Behavioral reflection is a powerful approach for adapting the behavior of running applications. In this paper we present and motivate partial behavioral reflection , an approach to more efficient and flexible behavioral reflection. We expose the spatial and temporal dimensions of such reflection, and propose a model of partial behavioral reflection based on the notion of hooksets . In the context of Java, we describe a reflective architecture offering appropriate interfaces for static and dynamic configuration of partial behavioral reflection at various levels, as well as Reflex, an open reflective extension for Java implementing this architecture. Reflex is the first extension that fully supports partial behavioral reflection in a portable manner, and that seamlessly integrates load-time and runtime behavioral reflection. The paper shows preliminary benchmarks and examples supporting the approach. The examples, dealing with the observer pattern and asynchronous communication via transparent futures, also show the interest of partial behavioral reflection as a tool for open dynamic Aspect-Oriented Programming.