An application server represents a framework for server applications, which are programs that provide an API rather than a GUI and allow remote access to their functionality. The architecture of the java-based applica...
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This paper presents a novel development method for interactive and distributed applications. The benefit that this method provides is that the design gives clear guidance towards the implementation. The method is base...
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This paper presents a novel development method for interactive and distributed applications. The benefit that this method provides is that the design gives clear guidance towards the implementation. The method is based on three main elements: a concept of synchronous active objects that is closely related to that found in CSP;the java environment;and a selection of the diagrams defined by UML. This approach alleviates many of the most serious problems that are encountered when using GUI builders, which hide the application structures and so make it difficult to devise sound architectures. The final part of the paper briefly describes an application generator that will help a developer to implement a design which is developed according to the approach advocated here.
This paper presents the design and implementation of java-based tools for accurate bandwidth measurement for xDSL (Digital Subscriber Line) networks, including the ADSL (Asymmetric DSL) case with different upstream an...
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This paper presents the design and implementation of java-based tools for accurate bandwidth measurement for xDSL (Digital Subscriber Line) networks, including the ADSL (Asymmetric DSL) case with different upstream and downstream bandwidths. First, a multi-packet bandwidth measurement technique is presented, based on the integration of packet-pair and filtering techniques. Considering the importance of a traffic generator to accurate measurement, a smooth and stable traffic generator is studied. We also present a stepwise algorithm designed to minimize the effect of ATM traffic shaping on the bandwidth measurements in xDSL deployments. Implementation details of the components of the java-applet- and java-application-based tools are described. Finally, evaluation experiments in both a laboratory testbed and a commercial ADSL network demonstrate that these tools achieve accurate bandwidth measurement in xDSL networks, and offer better performance than other popular tools such as pathchar and clink in terms of accuracy and usability.
We demonstrate a model, including operational semantics, for the reverse execution of stack-based code. We discuss our modification of the Kaffe implementation of the java Virtual Machine, supporting a debugger capabl...
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We demonstrate a model, including operational semantics, for the reverse execution of stack-based code. We discuss our modification of the Kaffe implementation of the java Virtual Machine, supporting a debugger capable of running java bytecode backwards. We achieve reverse execution by logging the state lost during each operation or by directly reversing instructions. Our debugger has facilities for stepping, stepping over methods and running to breakpoints, in both directions. Multi-threading is supported. It is also possible to step through the bytecode when the java source code is not available. The debugger has both a command line user interface and a graphical user interface with facilities for editing code and running the java compiler.
The distinct feature of data acquisition for magnetic resonance imaging (MRI) is that the data are sampled in frequency domain instead of spatial domain. Therefore, the acquired data must be inverse Fourier transforme...
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The distinct feature of data acquisition for magnetic resonance imaging (MRI) is that the data are sampled in frequency domain instead of spatial domain. Therefore, the acquired data must be inverse Fourier transformed to generate images. To apply fast Fourier transform (FFT), the data are usually acquired on rectilinear grids. However, acquiring data on rectilinear grids is not very efficient in MRI. A spiral trajectory, which starts at the origin of the frequency domain and spins out to higher spatial frequency is more efficient and faster than the conventional method. Since the spiral trajectories do not sample on rectilinear grids, raw data must be re-interpolated onto rectilinear grids prior to inverse FFT. This re-gridding process is done using a reconstruction program. When the platforms to run the program grow, the efforts required to maintain the program become prohibitive. This problem can be solved through the platform-independent java programming language. In this paper, we report on our attempt to implement the spiral MRI reconstruction program in java. We show that the performance is not significantly affected and that it is practical to use a platform-independent reconstruction software. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
We describe ConTest, a tool for detecting synchronization faults in multithreaded java(TM) programs. The program under test is seeded with a sleep(), yield(), or priority() primitive at shared memory accesses and sync...
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We describe ConTest, a tool for detecting synchronization faults in multithreaded java(TM) programs. The program under test is seeded with a sleep(), yield(), or priority() primitive at shared memory accesses and synchronization events. At run time, ConTest makes random or coverage-based decisions as to whether the seeded primitive is to be executed. Thus, the probability of finding concurrent faults is increased. A replay algorithm facilitates debugging by saving the order of shared memory accesses and synchronization events.
Distributed system performance depends on many aspects-data intensity, number of invocations, and required degree of interoperability. For developers who need the interoperability of a Corba implementation, remote met...
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Distributed system performance depends on many aspects-data intensity, number of invocations, and required degree of interoperability. For developers who need the interoperability of a Corba implementation, remote method invocation (RMI) and Internet InterORB Protocol (IIOP) relieve developers of such complexities. Companies looking for a simpler way to achieve interoperability should strongly consider these models.
Since java security relies on the type-safety of the JVM, many formal approaches have been taken in order to prove the soundness of the JVM. This paper presents a new formalization of the JVM and proves its soundness....
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Since java security relies on the type-safety of the JVM, many formal approaches have been taken in order to prove the soundness of the JVM. This paper presents a new formalization of the JVM and proves its soundness. It is the first model to employ dynamic linking and bytecode verification to analyze the loading constraint scheme of java2. The key concept required for proving the soundness of the new model is augmented value typing, which is defined from ordinary value typing combined with the loading constraint scheme. In proving the soundness of the model, it is shown that there are some problems inside the current reference implementation of the JVM with respect to our model. We also analyze the findClass scheme, newly introduced in java2. The same analysis also shows why applets cannot exploit the type-spoofing vulnerability reported by Saraswat, which led to the introduction of the loading constraint scheme.
The application of java in contacting business registries such as Universal Description, Discovery, and Integration (UDDI) and retrieve information from them, is analyzed. The information from a UDDI registry is conta...
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The application of java in contacting business registries such as Universal Description, Discovery, and Integration (UDDI) and retrieve information from them, is analyzed. The information from a UDDI registry is contained in four data structures. A UDDI registry is intended to be accessed programmatically via an API based on XML. The tools needed to query a UDDI registry are available and easy to use, and the java application programming interface (API) for XML messaging (JAXM) is suitable to prepare simple object access protocol (SOAP) messages.
Issues pertaining to mechanisms which can be used to change the behaviour of java classes at runtime are discussed. The proxy mechanism is compared to, and contrasted with other standard approaches to this problem. So...
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Issues pertaining to mechanisms which can be used to change the behaviour of java classes at runtime are discussed. The proxy mechanism is compared to, and contrasted with other standard approaches to this problem. Some of the problems the proxy mechanism is subject to are 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 runtime behaviour of externally-developed code. The issues addressed include ensuring type safety, dealing with the self problem, object encapsulation, and issues of object identify and equality. Some performance figures are provided which demonstrate the load the javaCloak proxy mechanism places on the system.
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