面向服务概述.ppt

Multi-Tier System Architecture RPC-based Client and middleware server is tightly coupled Remote Object based Remote objects communicates through standard interface languages Object models: OMG CORBA, SUN Java RMI, MS DCOM Web based Browser + “Dynamic content generation” Enabling techniques: CGI, Java Servlet/JSP, MS ASP * * Distributed Object Computing Coupled with a powerful communications infrastructure, distributed objects divide monolithic client/server applications into self-managing components, or objects, that can interoperate across disparate networks and operating systems. SUN J2EE JavaTM 2 Platform, Enterprise Edition MS DCOM Distributed Component Object Model OMG CORBA Common Object Request Broker Architecture * * Middleware In a distributed computing system, middleware is defined as the software layer that lies between the operating system and the applications on each site of the system. It serves to glue together or mediate between separate components. Objectives Hiding distribution Hiding the heterogeneity Providing uniform, standard, high-level interfaces Supplying a set of common services Examples Transaction processing monitors Data converters Communication controllers * * Middleware Design Challenges Performance Scalability Complexity of administration Mobility and dynamic reconfiguration Global information network to manage large applications that are heterogeneous, widely distributed and in permanent evolution * * CORBA – A bit of history OMG Standard, “to allow applications to communicate with one another no matter where they are located or who has designed them” 1991, CORBA 1.1, IDL API within an ORB 1994, CORBA interoperability IIOP (Internet Inter-ORB Protocol) 2002, CORBA Component Model * * CORBA – Objectives Distributed object computing middleware that shields applications from heterogeneous platform dependencies. To simplify development of distributed applications by automating/encapsulating Object location Connection memory mgmt