Java线程迁移机制的研究

从计算机集群系统实际应用出发,首先对Java线程的状态进行了分析,介绍了目前Java线程迁移机制的几种实现方法：处理源代码、处理字节码和扩展Java虚拟机的实现机制.从3个不同的方面进行了性能分析和比较,得出一个初步的评估.最后提出了一种扩展Java虚拟机方法的改进以及该迁移技术在集群系统中的应用.     

一个基于Java虚拟机的分布式计算模型

针对单个JVM的性能缺陷问题,分析了实现分布式JVM的关键技术,提出了一个基于Spaces的分布式虚拟机集成模型,该模型将执行代码和数据分离,通过异步协作机制和动态装载类技术,将多个Java作业透明地调度到不同的JVM资源上并行执行,实现了单一系统映象。     

Transparent migration of Java-based mobile agents: Capturing and re-establishing the state of Java programs

In this paper we describe a way to save and restore the state of a running Java program. We achieve this on the language level, without modifying the Java virtual machine, by instrumenting the programmer's original code with a preprocessor. The automatically inserted code saves the runtime information when the program requests state saving and re-establishes the program's runtime state on restart. The current preprocessor prototype is used in a mobile agent scenario to offer transparent agent migration for Java-based mobile agents, but could generally be used to save and re-establish the execution state of any Java program.     

一种嵌入式Java芯片内核—JC401

首先分析了目前Java的应用情况,指出嵌入式Java芯片具有很大的市场需求,然后结合嵌入式系统的特点简单分析了当前几种Java虚拟机实现技术的缺点,提出了在嵌入式Java芯片内核JC401中采用瘦型JIT的设计思想。通过对JIT的硬件支持和相关软件的配合,达到减少JIT运行时间和内存开销,获得高效的Java性能与较好的性能价格比的目标,然后具体介绍了JC401内核的总体结构与主要技术特点,进行了性能分析与评估,证明了设计思想的正确性,最后举例说明JC401具有很好的市场前景。     

VCluster: a thread‐based Java middleware for SMP and heterogeneous clusters with thread migration support

Clusters, composed of symmetric multiprocessor (SMP) machines and heterogeneous machines, have become increasingly popular for high‐performance computing. Message‐passing libraries, such as message‐passing interface (MPI) and parallel virtual machine (PVM), are de facto parallel programming libraries for clusters that usually consist of homogeneous and uni‐processor machines. For SMP machines, MPI is combined with multithreading libraries like POSIX Thread and OpenMP to take advantage of the architecture. In addition to existing parallel programming libraries that are in C/C++ and FORTRAN programming languages, the Java programming language presents itself as another alternative with its object‐oriented framework, platform neutral byte code, and ever‐increasing performance. This paper presents a new parallel programming model and a library, VCluster, which implements this model. VCluster is based on migrating virtual threads instead of processes to support clusters of SMP machines more efficiently. The implementation uses thread migration, which can be used in dynamic load balancing. VCluster was developed in pure Java, utilizing the portability of Java to support clusters of heterogeneous machines. Several applications are developed to illustrate the use of this library and compare the usability and performance of VCluster with other approaches. Copyright © 2007 John Wiley & Sons, Ltd.     

基于Java实现移动Agent强迁移的方法

对比分析了常见的移动Agent强迁移与弱迁移,提出一种基于Java实现移动Agent强迁移的方法.该方法基于IBMJikesRvm(Jikes research virtual machine(RVM))提供的RVM,利用OSR(on-stack replacement)捕捉运行堆栈的状态,实现了移动Agent强迁移.该方法不需要对源代码或字节码进行预处理,也不需要改变JVNI,具有很好的系统扩展性.     

基于Java的移动Agent强迁移技术研究综述

移动Agent强迁移技术已经成为当前移动Agent研究的热点。该文对基于Java语言的移动Agent强迁移技术的若干关键问题进行了归纳和总结,简述了几个典型系统的强迁移实现方法,讨论了这些方法各自的特点。对在Java环境中实现移动Agent强迁移提出了观点和建议。     

Implementing associations: UML 2.0 to Java 5

A significant current software engineering problem is the conceptual mismatch between the abstract concept of an association as found in modelling languages such as UML and the lower level expressive facilities available in object-oriented languages such as Java. This paper introduces some code generation patterns that aid the production of Java based implementations from UML models. The work is motivated by a project to construct model driven development tools in support of the construction of embedded systems. This involves the specification and implementation of a number of meta-models (or models of languages). Many current UML oriented tools provide code generation facilities, in particular the generation of object-oriented code from class diagrams. However, many of the more complex aspects of class diagrams, such as qualified associations are not supported. In addition, several concepts introduced in UML version 2.0 are also not supported.The aim of the work presented in this paper is to develop a number of code generation patterns that allow us to support the automatic generation of Java code from UML class diagrams that support these new and complex association concepts. These patterns significantly improve the code generation abilities of UML tools, providing a useful automation facility that bridges the gap between the concept of an association and lower level object-oriented programming languages.     

EJVM: an economic Java run‐time environment for embedded devices

As network‐enabled embedded devices and Java grow in their popularity, embedded system researchers start seeking ways to make these devices Java‐enabled. However, it is a challenge to apply Java technology to these devices due to their shortage of resources. In this paper, we propose EJVM (Economic Java Virtual Machine), an economic way to run Java programs on network‐enabled and resource‐limited embedded devices. Espousing the architecture proposed by distributed JVM, we store all Java codes on the server to reduce the storage needs of the client devices. In addition, we use two novel techniques to reduce the client‐side memory footprints: server‐side class representation conversion and on‐demand bytecode loading. Finally, we maintain client‐side caches and provide performance evaluation on different caching policies. We implement EJVM by modifying a freely available JVM implementation, Kaffe. From the experiment results, we show that EJVM can reduce Java heap requirements by about 20–50% and achieve 90% of the original performance. Copyright © 2001 John Wiley & Sons, Ltd.     

Mobile Java RMI support over heterogeneous wireless networks: A case study

Distributed object-oriented platforms are increasingly important in wireless environments to provide frameworks for collaborative computation and for managing a large pool of distributed resources. One of the important layers for implementing distributed computing in such environments is via remoting mechanisms. For example, Java uses Remote Method Invocation (RMI) for handling distributed controls. In this paper, we investigate the support for this important layer on wireless environments and address the issues to support Java RMI over heterogeneous wireless environments. We present a case study for supporting Java RMI in Bluetooth, GPRS, and WLAN environments, which represents an important middleware for component communications. The Bluetooth layer is supported by incorporating a set of protocol stack layers for Bluetooth, known as JavaBT that has been developed by us, and by supporting an L2CAP layer with sockets to support Java RMI sockets. RMI over GPRS/WLAN is achieved by RMI implementation over IP layer. Our support for the roaming of Java RMI over heterogeneous wireless networks is based on the concept of direct connection, which avoids the problems caused by forwarding. The difficulty of this strategy is how to handle the existing connection when the mobile node moves to another location so as to avoid interruption of the high-level applications. We solve this problem in Java RMI by the support of dynamic addresses and dynamic sockets. We also propose algorithms to handle the handoff process. In addition, methods for connect-loss detection and data-integrity maintenance in dealing with roaming scenarios are also presented. Java Grande benchmarks are used to demonstrate that our RMI implementations over GPRS, WLAN, and Bluetooth networks are effective in supporting parallel and distributed control of Java layers in heterogeneous wireless environments.     

A grid middleware for distributed Java computing with MPI binding and process migration supports

“Grid” computing has emerged as an important new research field. With years of efforts, grid researchers have successfully developed grid technologies including security solutions,resource management protocols, information query protocols, and data management services. How-ever, as the ultimate goal of grid computing is to design an infrastructure which supports dynarnic,cross-organizational resource sharing, there is a need of solutions for efficient and transparent task re-scheduling in the grid. In this research, a new grid middleware is proposed, called G-JavaMPI. This middleware adds the parallel computing capability of Java to the grid with the support of a Grid-enabled message passing interface (MPI) for inter-process communication between Java processes executed at dif-ferent grid points. A special feature of the proposed G-JavaMPI is the support of Java process migration with post-migration message redirection. With these supports, it is possible to migrate executing Java process from site to site for continuous computation, if some site is scheduled to be turned down for system reconfiguration. Moreover, the proposed G-JavaMPI middleware is very portable since it requires no modification of underlying OS, Java virtual machine, and MPI package. Preliminary performance tests have been conducted. The proposed mechanisms have shown good migration efficiency in a simulated grid environment.     

Java语言七巧板手机游戏设计

该文以Java语言作为程序的开发工具,从整体思路到部分功能的实现等介绍了七巧板游戏的设计。     

Machine learning techniques to predict sensitive patterns to fault attack in the Java Card application

Fault attack represents one of the serious threats against Java Card security. It consists of physical perturbation of chip components to introduce faults in the code execution. A fault may be induced using a laser beam to impact opcodes and operands of instructions. This could lead to a mutation of the application code in such a way that it becomes hostile. Any successful attack may reveal a secret information stored in the card or grant an undesired authorisation. We propose a methodology to recognise, during the development step, the sensitive patterns to the fault attack in the Java Card applications. It is based on the concepts from text categorisation and machine learning. In fact, in this method, we represented the patterns using opcodes n-grams as features, and we evaluated different machine learning classifiers. The results show that the classifiers performed poorly when classifying dangerous sensitive patterns, due to the imbalance of our data-set. The number of dangerous sensitive patterns is much lower than the number of not dangerous patterns. We used resampling techniques to balance the class distribution in our data-set. The experimental results indicated that the resampling techniques improved the accuracy of the classifiers. In addition, our proposed method reduces the execution time of sensitive patterns classification in comparison to the SmartCM tool. This tool is used in our study to evaluate the effect of faults on Java Card applications.     

Java虚拟机在ARM—Linux平台的移植研究

本文所讨论的是在嵌入式Linux系统下的Java运行环境的实现。论述了开放源代码的Java虚拟机（JamVM）和Java核心类库（GNU Classpath）ARM—Linux平台的裁减和移植。     

Klava: a Java package for distributed and mobile applications

Highly distributed networks have now become a common infrastructure for wide‐area distributed applications whose key design principle is network awareness, namely the ability to deal with dynamic changes of the network environment. Network‐aware computing has called for new programming languages that exploit the mobility paradigm as a basic interaction mechanism. In this paper we present the architecture of KLAVA , an experimental Java package for distributed applications and code mobility. We describe how KLAVA permits code mobility by relying on Java and present a few distributed applications that exploit mobile code programmed in KLAVA . Copyright © 2002 John Wiley & Sons, Ltd.     

一个基于混合并发模型的Java虚拟机

从解释执行到及时编译的转变极大地提高了Java程序的运行速度.但是,现有的Java虚拟机还有待进一步的改进.提出了一种新的Java虚拟机编译与执行模型--混合并发模型HCCEM(hybrid concurrent compilation and execution model).该模型通过多线程控制方式将字节码的编译与执行过程相重叠,从而获取加速的效果.另外还给出了基于HCCEM的Java虚拟机JAFFE的设计方案,并就实现中的执行模式切换、异常处理以及层次线程等问题进行了讨论.实验结果表明,HCCEM能     

一种基于Java虚拟机的动静结合自适应优化方法

动态语言可以利用程序运行时获取的动态信息,指导程序进行各种优化。但是,现有的Java虚拟机没有将运行过程中收集的信息有效利用,而是在运行结束后直接丢弃,下一次执行程序的时候重新监测、收集、优化需要的信息。基于HotSpot虚拟机提出一种动静结合的自适应优化方法,将运行过程中优化对象迭代搜索到的最佳参数或者信息保存到资源库中;能够从资源库中学习获得适合当前程序的最佳参数或选项,可有效地利用运行过程中积累的数据;资源分析是静态且离线的,不占用应用程序运行的开销;迭代学习的过程中,通过避免冗余实例入库以及从库中剔除噪声实例,保证资源库学习过程的精度与效率。实验表明,该框架对指导Java虚拟机在不同的平台上自适应优化具有一定的实用性。     

Java虚拟机动态类加载的形式化模型

Java虚拟机支持一种功能很强的动态加戡类的机制．它具有惰性加戡、类型安全连接、用户自定义加戡策略、以及劝态名字空间等特性。但是,在Java的早期实现(JDK1．0和1．1)中,这种机制包含了一种称为类型欺骗的严重设计错误．尽管JDK1．2通过引入一种类加戡约束策略修正了这个错误,但是由动态加戡引起的其它形式的类型欺骗仍然存在于JDK1．2和1．3中。本文详细讨论了与动态类加戡相关的类型欺骗问题,提出了一个严格定义Java虚拟机操作语义和静态语义的形式化模型。其中,操作语义描述了类加戡约束策略、字段及方法解析算法等类加戡的主要特性;静态语义采用类型规修正了JDK1．2和1．3中的类型欺骗。     

Ann: A domain-specific language for the effective design and validation of Java annotations

This paper describes a new modelling language for the effective design and validation of Java annotations. Since their inclusion in the 5th edition of Java, annotations have grown from a useful tool for the addition of meta-data to play a central role in many popular software projects. Usually they are not conceived in isolation, but in groups, with dependency and integrity constraints between them. However, the native support provided by Java for expressing this design is very limited.To overcome its deficiencies and make explicit the rich conceptual model which lies behind a set of annotations, we propose a domain-specific modelling language. The proposal has been implemented as an Eclipse plug-in, including an editor and an integrated code generator that synthesises annotation processors. The environment also integrates a model finder, able to detect unsatisfiable constraints between different annotations, and to provide examples of correct annotation usages for validation. The language has been tested using a real set of annotations from the Java Persistence API (JPA). Within this subset we have found enough rich semantics expressible with Ann and omitted nowadays by the Java language, which shows the benefits of Ann in a relevant field of application.     

JEETuningExpert: A software assistant for improving Java Enterprise Edition application performance

Designing a JEE (Java Enterprise Edition)-based enterprise application capable of achieving its performance objectives is rather hard. Predicting the performance of this type of systems at the design level is difficult and sometimes not viable, because this requires having precise knowledge of the expected load conditions and the underlying software infrastructure. Besides, the requirement for rapid time-to-market leads to postpone performance tuning until systems are developed, packaged and running. In this paper we present a novel approach for automatically detecting performance problems in JEE-based applications and, in turn, suggesting courses of actions to correct them. The idea is to allow developers to smoothly identify and eradicate performance anti-patterns by automatically analyzing execution traces. The approach has been implemented as a tool called JEETuningExpert, and validated using three well-known JEE reference applications. Specifically, we evaluated the effectiveness of JEETuningExpert for detecting performance problems, measured the overhead imposed by online monitoring each application and the improvements were achieved after following the suggested corrective actions. These results empirically showed that the refactored applications are 40.08%, 76.94% and 61.13% faster, on average.