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INF 123 SW Arch, dist sys & interop Lecture 9

INF 123 SW Arch, dist sys & interop Lecture 9. Prof. Crista Lopes. Objectives. Understanding of Distributed Objects architectures Acquaintance with a well-known RMI framework Java RMI. Web Services isa Distributed System.

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INF 123 SW Arch, dist sys & interop Lecture 9

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  1. INF 123 SW Arch, dist sys & interopLecture 9 Prof. Crista Lopes

  2. Objectives • Understanding of Distributed Objects architectures • Acquaintance with a well-known RMI framework • Java RMI

  3. Web Services isa Distributed System • “Collection of interactingcomponentshosted on different computers that are connected through a computer network” … Component n Component n Component n Component1 Component1 Component1 Network Network OS Network OS Network OS Hardware Hardware Hardware Host 2 Host 1 Host 3

  4. Remote Procedure Calls (RPC) Local Procedure Calls Remote Procedure Calls host 1 host program program caller caller r = foo(a, b) r = foo(a, b) host 2 callee program callee define foo(a, b) … end define foo(a, b) … end

  5. Remote Procedure Calls (RPC) Local Procedure Calls Remote Procedure Calls host 1 host program program caller caller r = foo(a, b) r = foo(a, b) Stub host 2 callee program Skeleton callee define foo(a, b) … end define foo(a, b) … end

  6. RPC Procedure Call Program (in PL) Procedure Interface Definition (in IDL) Procedure Definition Program (in PL) generates Stub (in PL) Skeleton (in PL) Network OS Network OS

  7. RPC Stubs • Marshal arguments (i.e. “serialize”) • Issue request to remote server, wait for response • Unmarshal return value (i.e. “deserialize”)

  8. RPC Skeletons • Unmarshal arguments • Call local procedure • Marshal return value • Send back response to client

  9. Distributed Objects model Obj2 Obj1 Obj3 Host A Host A Obj5 Obj4 Obj6 Host A Host A

  10. Distributed Objects model Obj2 Obj1 Obj3 Obj5 Obj4 Obj6 “Transparent distribution”

  11. Distributed Objects – Properties • Very tightly coupled with PL • Compiler generates stubs and skeletons • Distribution seen only in terms of peripheral components: • Security • Registry • Additional program arguments • Location (host) doesn’t matter [much] • Remote object references do

  12. Rest of this lecture • Java RMI tutorial athttp://java.sun.com/docs/books/tutorial/rmi/overview.html

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