Distributed Objects Technologies:
.NET and CORBANaim R. El-Far, PhD Candidate
TA for SEG3202 Software Design and Architecture with N. El-Kadri (Summer 2005)
Tutorial 4 of 4 – 24/6/2005
About Today’s Material
Some of today’s material has been adapted from presentations by D. Schmitt of Microsoft, and Dr. I. Stoica of UC Berkeley.
In Perspective
1. Client/Server Architecture (Tutorial 1)2. N-Tier Architecture (Tutorial 2)3. Concept of Distributed Objects (Tutorial
3)4. Technologies for Distributing Objects
Java RMI J2EE (Tutorial 3).NET (Today’s tutorial)CORBA (Today’s tutorial)
.NET Enterprise Vision
SchedulingAuthentication
Notification
ERP & Billing
Customer Operations Sales Supply Engineering
CustomerService
Plant Operations
UsersAny device,Any place,Any time
Roles/ExperiencesGet the right infoTo the right userAt the right time
XML Web ServicesIntegrate and orchestrate business applications and processes
Back OfficeHeterogeneous application and server infrastructure
What is .NET?
A generic term for the MS vision The successor to Windows DNA Sometimes applied to product names
Such as Windows .NET ServerA specific software framework
Includes a common runtime Common across OS and dev language
Includes baseline dev tools in an SDK Includes powerful dev environment
Visual Studio .NET
.NET Workings
An evolution from COM/DCOM Windows DNA .NET Platform-independent Internet integration Security
Primary Components Common Language Infrastructure (CLI): specifications
for a runtime environment, including a common type system, base class library, and a machine-independent intermediate code known as the Common Intermediate Language (CIL) – MSIL.
Common Language Runtime (CLR): Runtime environment to run any CIL code that adheres to CLI specs usually through JIT compilation.
.NET Workings All CIL is self-describing through .NET metadata. Language implementation CIL CLR MSIL .NET
languages .NET assemblies, DLL or EXE for Win32. The .NET unit of
deployment, versioning and security (64 bit public/private key). All code is compiled, not interpreted
Converted to native machine code at install time (via NGEN) or run time (via JIT compiler)
Static code management Versioning, localizing, and signing Configurable assembly resolver Global assembly cache (GAC)
Dynamic code management Memory allocation with garbage collection Lifecycle management via reference tracking Thread pooling
.NET Workings
Fine-grained code access security Augments OS security (user credentials) Ensures that code only performs operations allowed by policies
set by user or administrator Based on code source, publisher signature, and other evidence
Flexible deployment Simple XCOPY (since not bound to Windows registry) Windows installer Auto-deploy (aka no-touch or zero-impact)
Flexible remoting Includes XML/SOAP and binary Remoting model is easily extended Integrates with web services
ExecutionExecution
CodeCode
MetadataMetadata
Compilation & Execution
CompilationCompilation
Before Before installation or installation or the first time the first time
each method is each method is calledcalled
JIT JIT CompilerCompiler
NativeNativeCodeCode
Source Source CodeCode
Language Language CompilerCompiler
AssemblyUnit of deployment,
similar to DLL or EXE with added metadata
Saved in cacheAn assembly can also
be pre-compiled as part of deployment
CLR Internals
Class LoaderClass Loader
IL to NativeIL to NativeCompilersCompilers
CodeCodeManagerManager
GarbageGarbageCollectorCollector
Security ServicesSecurity Services Debug ServicesDebug Services
Type CheckerType Checker Exception ManagerException Manager
Thread ManagerThread Manager COM MarshalerCOM Marshaler
Base Class LibraryBase Class Library
C#C# VBVB
ASP.NET ADO.NET Enterprise Services
CLR
MSMQMSMQ COM+COM+ ActiveActiveDirectoryDirectory IISIIS WMIWMI
Win32Win32
.NET Structure: CLR and Win32 Services
J#...J#... Same class library across all programming
languages
Connects .NET to COM+ for transactional
components and other enterprise services
Connects .NET to data providers, including
XML documents
Provides WebForms for thin clients, plus web
services via HTTP
.NET Framework: More generally
.NET Framework
WindowsWindows
Standard .NETStandard .NETFrameworkFramework
WindowsWindows Framework ExtensionsFramework Extensions
Other Other FrameworkFrameworkExtensionsExtensions
Framew
ork Fram
ework
FeaturesFeatures
Application Reach across DevicesApplication Reach across Devices
Other OSOther OS
InternetInternet and Web Servicesand Web Services
.NET Mobility Framework
Windows CEWindows CE
.NET Compact .NET Compact FrameworkFramework
Windows CE Windows CE Framework ExtensionsFramework Extensions
Device Vendor Device Vendor FrameworkFrameworkExtensionsExtensions
Framew
ork Fram
ework
FeaturesFeatures
Application Reach across DevicesApplication Reach across Devices
Other OSOther OS
InternetInternet and Web Servicesand Web Services
.NET on non-MS Operating Systems
Microsoft’s Shared Source Initiative: Rotor: Microsoft shared-source version of .NET
for FreeBSD Mono: Novell (formerly by Ximian) open-source
version of .NET for GNU/Linux, UNIX, Mac OS X, and Windows based computers.
Portable .NET: is part of the DotGNU project.
Introduction to CORBA Common Object Request Broker Architecture (CORBA) A standard for software componentry. Created and controlled by the Object Management Group (OMG). Defines APIs, communication protocol, and object/service information models
to enable heterogeneous applications written in various languages running on various platforms to interoperate platform and location transparency for sharing well-defined objects across a distributed computing platform.
CORBA "wraps" code written in some language into a bundle containing additional information on the capabilities of the code inside, and how to call it. The resulting wrapped objects can then be called from other programs (or CORBA objects) over the network.
CORBA can be considered as a machine-readable documentation format. Interface Definition Language (IDL) to specify the interfaces that objects will
present to the world. A "mapping" from IDL to a specific implementation language like C++ or
Java. Standard mappings exist for Ada, C, C++, Lisp, Smalltalk, Java, and Python. There are also non-standard mappings for Perl and Tcl implemented by ORBs written for those languages.
High-Level Overview of CORBA CORBA applications are composed of objects. For each object type you define an interface in OMG IDL. CORBA = Separation of interface from implementation.
Well-defined, strict interfaces. Hidden implementation. Clients access objects only through their advertised interface.
CORBA Architecture
ORB
C++ Object
Client Server
Java Object
IIOPORB
Stub Object Adapter
Skeleton
Stub
Provides interface between client object and ORB
Marshalling: client invocationUnmarshalling: server response
ORB
C++ Object
Client Server
Java Object
IIOPORB
Stub Object Adapter
Skeleton
Skeleton
Provides iterface between server object and ORB
Unmarshaling: client invocationMarshaling: server response
ORB
C++ Object
Client Server
Java Object
IIOPORB
Stub Object Adapter
Skeleton
(Portable) Object Adapter (POA)
Register class implementationsCreates and destroys objects Handles method invokationHandles client authentication and access control
ORB
C++ Object
Client Server
Java Object
IIOPORB
Stub Object Adapter
Skeleton
Object Request Broker (ORB)
Communication infrastructure sending messages between objects
Communication type: GIOP (General Inter-ORB Protocol) IIOP (Internet Inter-ORB Protocol) (GIOP on TCP/IP)
ORB
C++ Object
Client Server
Java Object
IIOPORB
Stub Object Adapter
Skeleton
CORBA Object
Server
InterfaceIDL
C++/JavaImplementation
Interoperable Object ReferenceCORBA
Object
Servant
Example of CORBA Services
Naming: Keeps track of association between object names and their reference. Allows ORB to locate referenced objects
Life Cycle: Handles the creation, copying, moving, and deletion objects
Trader: A “yellow pages” for objects. Lets you find them by the services they provide
Event: Facilitates asynchronous communications through events
Concurrency: Manages locks so objects can share resources
Query: Locates objects by specified search criteria
Remote Invocation in CORBA
Oversimplification: Client first obtains its object reference (E.g. Naming Service and the Trader
Service). Remote invocation = local invocation + substituting the object reference for
the remote instance. ORB examines the object reference and discovers that the target object is
remote routes the invocation out over the network to the remote object's ORB.
Remote Invocation in CORBA
In more detail: IDL the client knows exactly which operations
it may invoke, what the input parameters are, and where they have to go in the invocation
IIOP (ORBs may use other protocols) Although the ORB can tell from the object
reference that the target object is remote, the client can not.
Object Invocation Models
Invocation models supported in CORBA
Request type Failure semantics DescriptionSynchronous At-most-once Caller blocks until a
response is returned or an exception is raised
One-way Best effort delivery Caller continues immediately without waiting for any response from the server
Deferred synchronous
At-most-once Caller continues immediately and can later block until response is delivered
Interoperability
Allow multi-vendor ORB implementations to communicate with each other
General Inter-ORB Protocol (GIOP) message types
Message type Originator Description
Request Client Contains an invocation request
Reply Server Contains the response to an invocation
LocateRequest Client Contains a request on the exact location of an object
LocateReply Server Contains location information on an object
CancelRequest Client Indicates client no longer expects a reply
CloseConnection Both Indication that connection will be closed
MessageError Both Contains information on an error
Fragment Both Part (fragment) of a larger message
Object References
The organization of an IOR with specific information for IIOP
Secure Object Invocation in CORBA
CORBA Application
1) Define interface using IDL2) Compile interface3) Implement interface4) Instantiate server:
• Register object as a CORBA object
5) Instantiate client:• Invoke CORBA object
• Example using a Java client and server
J2EE vs. .NET
Cola vs. Pepsi Are you starting from scratch? Are you migrating from a legacy system? One day, J2EE and .NET will become “legacy”
systems. Past, Present, and Future. Web Services Body Organs For more details (a little out of date by
comprehensive: http://www.theserverside.com/articles/article.tss?l=J2EE-vs-DOTNET)
Where does CORBA fit it?
Purpose of CORBAIIOP, a pillar of CORBAJ2EE support for IIOP.NET support for IIOP (IIOP.NET, Janeva)CORBA, J2EE, and .NET: like everything
else, the mix depends on your purpose, the past, the present, and the future of your system.