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Enterprise Computing

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Code (PERL, REXX, C, C ) run by webserver in response to client ... Borland just bought Visigenics. Borland's and Visigenics vision is a CORBA based world ... – PowerPoint PPT presentation

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Title: Enterprise Computing


1
Enterprise Computing
2
Possible Client Server Solutions
  • CGI (Common Gateway Interface)
  • Active Server Pages
  • 2 Tier Java
  • 3 Tier Java
  • Sockets
  • JavaIDL / CORBA
  • JavaRMI

3
CGI
  • Code (PERL, REXX, C, C) run by webserver in
    response to client request code creates a web
    page HTML in real time and returns to client
  • Old Technology pre- HTTP
  • reliable
  • resource hog

4
CGI (more)
  • Very useful used in conjunction with Java based
    clients for things like
  • Report Generation
  • Data retrieval
  • Persistant object storage
  • Could be replaced by server side Java servletts
  • Hard to maintain program state

5
CGI (more)
Static Web with forms tags ltform
action/CGI-BIN/AAA.PRLgt
Browser
Web Server
CGI Program
DB
6
CGI (more)
  • If another user requests a CGI while the CGI is
    already running the web server spawns a thread
    and runs another instance of the CGI there.
  • For frequently run CGIs many copies may be in the
    machine at the same time
  • …resource hog

7
CGI (more)
Browser
Browser
Browser
Web Server
DB
CGI Program
CGI Program
CGI Program
8
Active Server Pages
  • HTML pages
  • Embedded scripting language and proprietary
    server support are used to make forms objects
    appear to be database aware
  • Main contenders
  • Netscape One
  • Microsoft Active Server Pages
  • Cold Fusion

9
Netscape One
  • Core Technologies
  • HTML
  • Java JavaScript
  • Java Runtime Interface (JRI)
  • Netscape Suite Spot Server
  • Netscape Internet Foundation Classes (Java)
  • Netscape Live Connect
  • Netscape Live Wire
  • CORBA / ORB Technology

10
Netscape One (More)
  • Live Connect
  • Enables communication between JavaScript and Java
    applets
  • Live Wire
  • Enables web site management
  • Provides database connectivity between Netscape
    browser, HTML, JavaScript
  • special HTML-like tags

11
Netscape One (more)
HTML
Netscape Web Server
JavaScript
Java
LiveWire
LiveConnect
LiveWire
DB
12
Microsoft Active Server Pages
  • Core technologies
  • MS Internet Information Server
  • MS Internet Explorer (IE4.0)
  • VBScript
  • Java
  • ActiveX
  • SQL Server Access
  • DCOM

13
Microsoft Active Server Pages
  • Works only on Windows

14
Microsoft Active Server Pages
HTML
IIS
JavaScript VBScript
VBScript
Java
ActiveX
IE 4.0
DB
15
Cold Fusion
  • Core Technologies
  • Proprietary Scripting language
  • Java
  • Proprietary Cold Fusion Server (must run on same
    machine as the Webserver (any web server)

16
2-Tier Client Server
  • Java based Client application or applet
  • JDBC
  • Database

17
2-Tier Client-Server - application
Java Client Application using JDBC APIs
JDBC Enabled Database
TCP/IP
This application architecture is simple but wont
scale to very many users
18
2-Tier Client-Server - applet
Unix or Windows
Browser
HTML
Webserver
applet
JDBC Enabled DB
V 1.1 JVM
Webserver and DB must be on same IP address
19
2-Tier Problems
  • Client has to do everything
  • DBs arent meant to handle large numbers of
    simultaneous invocations
  • Good only for infrequently used apps

20
3-Tier Client-Server
  • Java based Client application or applet
  • Server/middleware
  • Database

21
3-Tier Client Server
Sockets JavaIDL JavaRMI
JDBC Native
Client
Client
Server
DB
Client
22
3-Tier Advantages
  • Server can manage database connections
    efficiently
  • Client can focus on business logic
  • Server can preformat data for client
  • Running server on high performance hardware can
    improve client perceived performance

23
JavaIDL
  • In Java we cannot separate a classs definition
    from its implementations we can in C
  • Header files
  • Implementation files
  • CORBA allows the separation of definition and
    implementation

24
JavaIDL
  • CORBA uses IDL for defining interfaces, language
    specific IDL compilers are available
  • create target language skeletons and stubs to be
    used by developers for building CORBA clients and
    servers
  • CORBA objects talk to each other via interfaces

25
CORBA Object Communications
IIOP
Object A
Object B
Interface
Interface
26
Conceptually ...
Client
Server
Client
Server
ORB
Client
Server
27
Really though...
Registration
ORB
1
Client
Server
Services
2
Client
Server
3
Client
Server
28
What happens...
  • Server objects register their methods with the
    orb naming service
  • Client binds to the orb naming server for a
    server object method
  • Naming service return location of server object
    and disconnects
  • Client connects to server at returned location

29
This is very simplified
  • Very…
  • The local ORB expert is Steve Woods and is
    currently working on an Orb based IRAD project

30
Orb Info
  • The Visigenics VisiBroker Orb is built into
    Netscape Communicator 4.0
  • Borland just bought Visigenics
  • Borlands and Visigenics vision is a CORBA based
    world
  • Why didnt Microsoft buy Visigenics?

31
Why MS didnt buyVisigenics
  • Wrong vision…
  • MS Vision is DCOM not CORBA

32
Remote Method Invocation
  • Similar to C RPCs
  • Instead of creating and instantiating an object
    on your machine create it on another machine and
    communicate with it as if it were a local object
  • eliminates CORBA overhead
  • comes with JDK 1.1

33
RMI
  • RMI classes let you generate stubs and skeleton
    layers like JavaIDL
  • Remote reference Layer translates stup and
    skeletion calls to native transport calls on the
    host architecture and carries out remote
    reference protocols

34
RMI Model
Client
Server
Stubs
Skeletons
Remote
Remote
Reference
Reference
Transport
35
RMI
  • Currently RMI uses its own on the wire protocol
  • Sun has committed to make the on the wire
    protocol IIOP
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