分布对象1

分布对象1内容摘要：

teract with local object proxies (stubs) and let the object distribution scheme handle munication behind the scenes 2020/11/4 Institute of Computer Software Nanjing University 35 分布计算的一般框架 2020/11/4 36 IDL Compilers Registration Service Object Skeleton Object Storage Object Manager Naming Service Client Application Server Implementation Client Stub Interface Object Interface Specification 运行时刻远程对象交互 2020/11/4 Institute of Computer Software Nanjing University 37 Object Stubs Server Object Implementation Object Skeleton Object Manager Naming Service Client Application 2. Resolve Object 4. Object Interactions 1. Request Object 3. Object Handle Comparing DOC Frameworks C r o s s C r o s s C o m p l e x i ty C l i e n t Se r v e r Se c u r i tyPl a tf o r m L a n g . Por ta b i l i ty Por ta b i l i tyC O R B A y e s y e s m e d i u m h i g h m e d i u m m a n y o p t i o n sD C O M l i m i t e d y e s h i g h l o w l o w N T s e c u ri t yR M I y e s no l o w h i g h h i g h a d d o n2020/11/4 Institute of Computer Software Nanjing University 38  Distributed Object Computing Frameworks  CORBA Common Object Request Broker Architecture, an industry standard developed by OMG  DCOM Microsoft’s Distributed Component Object Model, a descendant of DCE RPC  RMI Java’s Remote Method Invocation 摘要  背景 Why, What, How  一般框架  CORBA  Java RMI 2020/11/4 Institute of Computer Software Nanjing University 39 OMG Reference Model Architecture 2020/11/4 Institute of Computer Software Nanjing University 40 Object Management Architecture  Object Services  Domainindependent foundational services for use by developers of implementation objects  some published services: Naming: allows clients to find objects based on names Trading: allows clients to find objects based on their properties Lifecycle management Event notification Transactions Security „ 2020/11/4 Institute of Computer Software Nanjing University 41 Object Management Architecture  Common Facilities object services provide functionality for use by objects, CORBA facilities provide standards for services used by applications generic functionality needed by many applications (., printing, document management, , etc.) 2020/11/4 Institute of Computer Software Nanjing University 42 Object Management Architecture  Domain Interfaces provide domainspecific objects for vertical application domains Examples: Finance, Healthcare, Manufacturing, Tele, Electronic Commerce, Transportation  Application Interfaces  Thus not standardized 2020/11/4 Institute of Computer Software Nanjing University 43 Common Object Request Broker Architecture  一个典型的分布对象计算架构  The architecture 对象 Objects and Clients 接口 OMG IDL  “ 对象管理器” ORB 底层通信协议 IIOP 其他 2020/11/4 Institute of Computer Software Nanjing University 44 2020/11/4 Institute of Computer Software Nanjing University 45 Distributed Systems Frameworks 46 Overview of CORBA Objects  CORBA Object  identity, interface, implementation  CORBA objects differ from typical programming language objects:  CORBA objects can be located anywhere on a work.  CORBA objects (like Java objects) can run on any platform.  CORBA objects can be written in any of several languages.  CORBA object developers need know nothing of where their clients will be, what hardware or OS they will run on, or what language they will be written in.  CORBA objects approach universal accessibility. Distributed Systems Frameworks 47 Overview of CORBA Objects  An object implementation provides the semantics of the object, usually by defining data for the object instance and code for the object39。 s methods. (called a “servant”)  A client of an object has access to an object reference for the object, and invokes operations on the object.  A client knows only the logical structure of the object according to its interface and experiences the behavior of the object through invocations.  Client code has no knowledge of the implementation of the object or which ORB is used to access the implementation. Distributed Systems Frameworks 48 Role of OMG IDL ORB C C++ Ada I D L I D L I D L I D L I D L I D L Client Side Object Implementation Side COBOL C Ada C++ Small talk JAVA I D L I D L I D L I D L I D L I D L ORB ++ COBOL Small talk JAVA Inter InterORB Protocol (IIOP) Distributed Systems Frameworks 49 OMG IDL  OMG Interface Definition Language (IDL):  mappings for many languages/pilers。  independent of any particular language/piler。  multipleinheritance, public interfacestructured specification language。  not for implementation.  primary support for interoperability between static and dynamic requests mechanisms. Distributed Systems Frameworks 50 OMG IDL  IDL Structure  Module  a namespace  Interface  abstract type  multiple inheritance  Struct  structured data Module auction { exception NotAllowed {}。 struct Sale { int price。 string item。 } interface Auction { void bid (in long price) raises NotAllowed。 } } Distributed Systems Frameworks 51 Client Object Implementation ORB Request A Request  A request consists of:  Target object (target object identified by a unique object reference)  Operation  Parameters (the input, output and inout parameters defined for the operation。 may be spe。