基于J2EE在分布式环境下的底层结构的自动动态配置的应用 Infrastructure for Automatic Dynamic Deployment Of J2EE Application in Distributed Environments

s’ resources, • provide these facilities without incurring significant additional design effort on behalf of application programmers. In this paper we propose the infrastructure for automatic dynamic deployment of J2EE applications, which addresses all of the aforementioned issues. The infrastructure defines architecture description languages (ADL) for component and link description and assembly. The Component Description Language is used to describe application components and links. It provides clear separation of application components from system components. A flexible type system is used to define compatibility of component ports and links. A declaration and expression language for configurable component properties allows for specification of inter-component dependencies and propagation of properties between components. The Component (Replica) Assembly Language allows for assembly of replicas of previously defined components into application paths by Connecting appropriate ports via link replicas and specifying the mapping of these component replicas onto target application server nodes. The Component Configuration Process evaluates an application path’s correctness, identifies the dependencies of application components on system components, and configures component replicas for deployment. An attempt is made to match and reuse any previously deployed replicas in the new path based on their configurations. We implement the infrastructure as a part of the JBoss open source Java application server [11] and test it on several Sample J2EE applications – Java Pets tore [23], Rubies [20] and TPC-W-NYU [32]. The infrastructure implementation utilizes the JBoss’s extendable micro-kernel architecture, based on the JMX [27] specification. Componentized architecture of JBoss allows incremental service deployments depending on the needs of deployed applications. We believe that dynamic reconfiguration of application servers through dynamic deployment and undeployment of system services is essential to building a resource-efficient framework for dynamic distributed deployment of J2EE applications. The rest of the paper is organized as follows. Section 2 provides necessary background for understanding the specifics of the J2EE component technology which are relevant to this study. Section 3 gives a general description of the infrastructure architecture, while section 4 goes deeper in describing particularly important and interesting internal mechanisms of the infrastructure. Section 5 describes the implementation of the framework, and related work is discussed in section 6. 2 J2EE Background 2.1 Introduction Component frameworks. A component framework is a middleware system that supports applications consisting of components conforming to certain standards. Application components are “plugged” into the component framework, which establishes their environmental conditions and regulates the interactions between them. This is usually done through containers, component holders, which also provide commonly required support for naming, security, transactions, and persistence. Component frameworks provide an integrated environment for component execution, as a result significantly reduce the effort .it takes to design, implement, deploy, and maintain applications. Current day industry component framework standards are represented by Object Management Group’s CORBA Component Model [18], Sun Microsystems’ Java 2 Platform Enterprise Edition (J2EE) [25] and Microsoft’s .NET [17], with J2EE being currently the most popular and widely used component framework in the enterprise arena. J2EE. Java 2 Platform Enterprise Edition (J2EE) [25] is a comprehensive standard for developing multi-tier enterprise Java applications. The J2EE specification among other things defines the following: • Component programming model, • Component contracts with the hosting server, • Services that the platform provides to these