Java语言与Java技术

介绍Ｊａｖａ语言对业界的影响，Ｊａｖａ平台及当前正在发展着的Ｊａｖａ技术。     

If Java is the answer, what was the question?

Within a very few short years, Java, Java Beans, and everything to do with Java will be pervasive. Java's adoption curve will rival just about everything else in Silicon Valley for living in real time. The technology will burn brightly for a time and then burn itself out. Before that happens, though, Java will be as common as a household mop. Product hype is as much a part of the computer industry as celebrity is an essential part of Hollywood. Excellence often falls victim to PR. In the case of Java, it is particularly difficult to separate the PR from the reality. So your first question might be, is Java really an improvement? Simply put, no. If today's languages are inadequate for today's software engineering challenges, then Java must be inadequate, too. Remember, most of Java is warmed-over C/C++. In spite of its celebrity status, Java lacks many of the features needed to improve the dismal science of software engineering, just like its predecessors. How so, you ask! The author presents an analysis-with a minimum of hype-on the pros and cons of Java     

Genericity in Java: persistent and database systems implications

Lack of parametric polymorphism has been a major obstacle for making Java a viable database programming language. Regrettably, a recently accepted solution for genericity in Java 5.0 has far-reaching negative implications for persistent and database systems because of static and dynamic type violations. Severe implications occur in typical database transactions when processing a variety of database collections. Well-known approaches to persistence in Java, including Java’s own persistence mechanism, do not perform correctly due to incorrect dynamic type information that gets promoted to persistence along with objects. Dynamic checking of types of objects fetched from the persistent store may now lead to unexpected type violations. Further problems occur in reflective transactions as Java Core Reflection now allows dynamic type violations without detecting them or throwing standard exceptions. All of this shows that extending Java with parametric polymorphism has not made Java a more viable database programming language. Both legacy systems, such as those based on the Java binding of the ODMG or JDO, and future Java-related persistent and database technologies will be affected. The source of these problems is in an implementation idiom called type erasure. This paper provides formal proofs of the above implications of type erasure along with specific samples of code in Java 5.0 illustrating these violations. The limitations of the virtual platform and extensions required for persistent systems to solve this problem are also elaborated.     

Integrating Java 3D model and sensor data for remote monitoring and control

This paper presents a novel approach and a framework for web-based systems that can be used in distributed manufacturing environments. A prototype is developed to demonstrate its application to remote monitoring and control of a Tripod—one type of parallel kinematic machine. It utilizes the latest Java technologies (Java 3D and Java Servlets) as enabling technologies for system implementation. Instead of using a camera for monitoring, the Tripod is modeled using Java 3D with behavioral control nodes embedded. Once downloaded from its server, the 3D model behaves in the same way of its counterpart at client side. It remains alive by connecting with the Tripod through message passing, e.g., sensor signals and control commands transmissions. The goal of this research is to eliminate network traffic with Java 3D models, while still providing users with intuitive environments. In the near future, open-architecture devices will be web-ready having Java virtual machines embedded. This will make the approach more effective for web-based device monitoring and control.     

Bringing Java to the enterprise: Oracle on its Java server strategy

Java is becoming the predominant language for defining and deploying complex business logic across all tiers of the enterprise. Java is uniquely suited to distributed information systems, and clearly critical to the success of Oracle's network computing initiative. No other language combines the features required in these environments. This paper surveys five aspects of our Java product strategy. Unless otherwise stated, these components are included in the Oracle 8.1 software development kit, SDK2, which is under test at a small number of sites. Over the past 20 years, SQL has become the “shape” of the world's store of data. In many ways, Java represents a practical, ubiquitous means for augmenting this structure with the arbitrarily complex operational semantics that only a general-purpose, object-oriented programming language can provide. Such logic is inherently distributed, and may be freely deployed on any network computing tier. The combination of ubiquitous SQL data and Java behavior will generalize relational database management systems into the information servers that are so critical to the future of network computing     

Java开发平台安全性分析

从Java体系结构对安全性的支持入手,用语言方面和Java平台提供的API功能方面研究Java开发平台对安全性的支持。     

基于J2ME的移动电子商务

电子商务通常在计算机和手机上进行，要求在网络实现方面必须具备跨平台的技术。Java语言在网络上有易用性、稳定性和安全性等优势．是计算机网络编程的首选语言，更重要的是Java语言体现出良好的跨平台性。使用Java语言的J2EE体系能实现移动电子商务的服务器端编程，而J2ME体系能实现电子商务的手机用户端编程。JavaServlet运行于服务器上，JavaMIDlet运行于用户手机，通过HTTP协议进行交互通讯，通过JDBC操作数据库进行信息读取和存储，完成商务活动。J2ME基于Java体系．有着良好的软硬件兼容性，代表了Internet移动电子商务实现技术的发展方向。     

64‐bit versus 32‐bit Virtual Machines for Java

The Java language is popular because of its platform independence, making it useful in a lot of technologies ranging from embedded devices to high‐performance systems. The platform‐independent property of Java, which is visible at the Java bytecode level, is only made possible thanks to the availability of a Virtual Machine (VM), which needs to be designed specifically for each underlying hardware platform. More specifically, the same Java bytecode should run properly on a 32‐bit or a 64‐bit VM. In this paper, we compare the behavioral characteristics of 32‐bit and 64‐bit VMs using a large set of Java benchmarks. This is done using the Jikes Research VM as well as the IBM JDK 1.4.0 production VM on a PowerPC‐based IBM machine. By running the PowerPC machine in both 32‐bit and 64‐bit mode we are able to compare 32‐bit and 64‐bit VMs. We conclude that the space an object takes in the heap in 64‐bit mode is 39.3% larger on average than in 32‐bit mode. We identify three reasons for this: (i) the larger pointer size, (ii) the increased header and (iii) the increased alignment. The minimally required heap size is 51.1% larger on average in 64‐bit than in 32‐bit mode. From our experimental setup using hardware performance monitors, we observe that 64‐bit computing typically results in a significantly larger number of data cache misses at all levels of the memory hierarchy. In addition, we observe that when a sufficiently large heap is available, the IBM JDK 1.4.0 VM is 1.7% slower on average in 64‐bit mode than in 32‐bit mode. Copyright © 2005 John Wiley & Sons, Ltd.     

多层分布式应用系统在Java中的实现

在分析了分布计算、JDBC和RMI等技术的基础上,提出了多层分布式应用系统在Java中的实现模型.同时,由于Java具有跨平台、可移植性、安全高效等强大功能,是开发网络分布式系统的理想工具.     

CORBA,DCOM和Java/RMI技术比较

分布式对象技术主要是在分布式异构环境下建立应用系统框架和对象构件,在应用系统框架的支撑下,开发者可以将软件功能包装为更易管理和使用的对象,这些分布式对象可以跨越不同的软硬件平台进行互操作。现在比较流行的三种重要的分布对象技术,它们是OMG的公对象请求代理体系结构(CORBA),Microsoft的分布式组件对象模型(DCOM),以及JavaSoft的Java/远程方法调用(Java/RMI)。本文将从编程人员以及架构师的角度,分析比较这三种分布对象技术之间的区别以及它们各自的优缺点。     

基于Java的多层系统模型研究

分析了传统体系结构的不足,提出了多层应用系统在Java中的实现模型.同时,由于Java具有跨平台、可移植性、安全高效等强大功能,是开发多层应用系统的理想工具.     

基于Internet和多传感器融合的工厂自动化专家网络

本文介绍了在未来网络化时代工业自动化中的一种基本技术框架－基于Ｉｎｔｅｒｎｅｔ环境和多传感器融合的专家网络。基于模糊逻辑和要素空间理论，我们试图开发适于各种工业应用的通用软件平台和硬件结构。系统是一种适合于工业自动化中的专家系统的专家机。人们使用ＨＴＭＬ和ｓｍａｒｔ ａｐｐｌｅｔｓ（用Ｊａｖａ语言编写的模糊逻辑算法小应用程序）来实现知识的获取，知识库的建立，知识的共享以及实时问题的解决。     

基于Java的多功能XML工作引擎

运用Java和XML技术开发的应用软件平台有很多优点,而采用电子邮件代替网络连接作为信息交换的载体能够增强系统的安全性,本文介绍了一个基于电子邮件的Java-XML工作引擎－XMLInterchange,重点描述XMLInterchange的设计,实验“并给出了一个XMLInterchange作为电子商务平台的应用实例－电子传单。     

智能化小区可视对讲系统中控制网络的设计

Java技术最初是通过客户端运行Applet来给网页增加交互性，将网络应用程序从静态的简单网页集合．提升到具有交互性的高级层次。由于基于B／S模式网络应用程序的发展，为了让Java平台在客户端发挥它的最大潜力，又有了许多新技术。文中。我们结合开发工作流设计的应用探讨并阐述了如何利用这些技术。     

客户端Java技术的应用

Java技术最初是通过客户端运行Applet来给网页增加交互性,将网络应用程序从静态的简单网页集合,提升到具有交互性的高级层次。由于基于B/S模式网络应用程序的发展,为了让Java平台在客户端发挥它的最大潜力,又有了许多新技术。文中,我们结合开发工作流设计的应用探讨并阐述了如何利用这些技术。     

基于J2EE的知识库管理系统的设计与实现

Java2平台中最重要的就是J2EE平台。基于层次化组件模式的J2EE平台把业务逻辑和底层网络技术分离出来，具有可伸缩性、可扩展性、易开发和易维护性，已经成为企业级商业分布式网络计算的事实标准。J2EE融合了各种网络技术和应用服务技术，它是仍在不断发展完善的平台。文中结合知识库管理系统的开发介绍了J2EE的基本特征，以及在J2EE平台基础上实现一个知识库管理系统的基本框架和相关的实现细节。     

The Object‐JavaScript language

Complex graphical user interfaces (GUIs) that support a large amount of user interaction require a fast response time, a rich set of building blocks for an esthetic look‐and‐feel, and a development environment that supports ongoing change. On the World Wide Web, client‐side technologies offer more of these features than do server‐side solutions. Java and JavaScript are the two most popular languages used for client‐side GUI implementations. Java implementations require a user to download a plug‐in that contains a virtual machine to execute the Java byte‐code. The installation and maintenance of this plug‐in is sometimes an unsurmountable barrier to using Java. JavaScript lacks some of the desirable features of Java, such as easy to use object‐oriented features and having a GUI class library, but does not require a plug‐in. We have enhanced JavaScript by implementing a new language Object‐JavaScript (OJS) and by providing an OJS library of GUI components, thus making it a viable alternative to Java. Copyright © 2000 John Wiley & Sons, Ltd.     

Mobile agents with Java: The Aglet API

Java, the language that changed the Web overnight, offers some unique capabilities that are fueling the development of mobile agent systems. In this article we will show what exactly it is that makes Java such a powerful tool for mobile agent development. We will also draw attention to some shortcomings in Java language systems that have implications for the conceptual design and use of Java-based mobile agent systems. Last, but not least, we will introduce the aglet – a Java-based agile agent. We will give an overview of the aglet and, its application programming interface, and present a real-world example of its use in electronic commerce.     

基于JavaEE的专业英语学习交流平台

本文借助于JavaEE环境,采用MVC模式,整合OScache、Log4j、JavaMail、AjaX＋Json、SHAI、Session、JavaI／O等技术,设计并实现了一个B／S架构的专业英语学习交流平台。该平台后台框架采用Spring3＋Struts2＋JDBCTemplate技术,前台页面使用JqueryEasyUI等技术来实现。该平台提供自动化专业英语课程的日常教学和学生个人自主学习等多种功能,具有使用方便、可移植性强、易于维护等特点。