毕业设计外文文献—Java虚拟机中的动态类加载.docxVIP

附录A 外文翻译—原文部分 Source: DynamicClass Loading in the Java VirtualMachine [J]. Author: Sheng Liang Gilad Bracha. Dynamic Class Loading in the Java Virtual Machine Class loaders are a powerful mechanism for dynamically loading software components on the Java platform. They are unusual in supporting all of the following features: laziness, type-safe linkage, user-de?ned extensibility, and multiple communicating namespaces. We present the notion of class loaders and demonstrate some of their interesting uses. In addition, we discuss how to maintain type safety in the presence of user-de?ned dynamic class loading. In this paper, we investigate an important feature of the Java virtual machine: dynamic class loading. This is the underlying mechanism that provides much of the power of the Java platform: the ability to install software components at runtime. An example of a component is an applet that is downloaded into a web browser. While many other systems[16] [13] also support some form of dynamic loading and linking, the Java platform is the only system we know of that incorporates all of the following features: 1. Lazy loading. Classes are loaded on demand. Class loading is delayed as long as possible, reducing memory usage and improving system response time. 2. Type-safe linkage. Dynamic class loading must not violate the type safety of the Java virtual machine. Dynamic loading must not require additional run-time checks in order to guarantee type safety. Additional link-time checks are acceptable, because these checks are performed only once. 3. User-de?nable class loading policy. Class loaders are ?rst-class objects. Programmers have complete control of dynamic class loading. A user-de?ned class loader can, for example, specify the remote location from which the classes are loaded, or assign appropriate security attributes to classes loaded from a particular source. 4. Multiple namespaces. Class loaders provide separate namespaces for different software components. Fo