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Session Facade vs. Business Delegate

Gennady Shapiro
Ranch Hand

Joined: Sep 25, 2001
Posts: 196
These two patterns are very similar functionally, except Session Facade is server-bound and Business Delegate is client bound. They both provide:
-reduced coupling
-increased managebility
-simpler interface
-better performance
-cetralized management (SF-resources,BD-exceptions)
Can someone (who actually had this on the exam) point out how Sun formulate the question about how to distinguish them and what are the hints? These are simple patterns but it's a very close call.
http://developer.java.sun.com/developer/technicalArticles/J2EE/patterns /J2EEPatternsRoadmap.html
Mark Spritzler
ranger
Sheriff

Joined: Feb 05, 2001
Posts: 17250
    
    6

In mine, they didn't have both of them as an answer
Mark


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Madhav Lakkapragada
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Joined: Jun 03, 2000
Posts: 5040
Can someone (who actually had this on the exam)
That pretty much eliminates me.....
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Ajith Kallambella
Sheriff

Joined: Mar 17, 2000
Posts: 5782
The options given in the test are very unambiguous and you simply cannot go wrong. I encountered two types of questions covering the patterns section
  • A business scenario is described and you are required to choose one( or more ) patterns that you would employ.
  • One or more features/benefits of a pattern is described in plain English. You are required to identify the pattern.


  • Hope that helps.


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    Paul Michael
    Ranch Hand

    Joined: Jul 02, 2001
    Posts: 697
    ...so what really are the differences between Session Facade and Business Delegate patterns?


    SCJP 1.2 (89%), SCWCD 1.3 (94%), IBM 486 (90%), SCJA Beta (96%), SCEA (91% / 77%), SCEA 5 P1 (77%), SCBCD 5 (85%)
    R K Singh
    Ranch Hand

    Joined: Oct 15, 2001
    Posts: 5371
    As far as I have gone through these topic at http://developer.java.sun.com/developer/restricted/patterns/J2EEPatternsAtAGlance.html and
    at http://java.sun.com/blueprints/patterns/j2ee_patterns/catalog.html
    I found that Session Facade is more about reducing network traffic and Bussiness Delegate is more about hiding complexities on client. Bussiness delegates can be thought of kind of wrapper for Server beans which hides reapeating code everytime likek lookup etc.
    CMIW
    HTH


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    Jeff Mychasiw
    Greenhorn

    Joined: Dec 13, 2001
    Posts: 5
    FYI,
    These patterns are explained very well in the Book: EJB Design Patterns. You can find a PDF at www.theserverside.com
    R K Singh
    Ranch Hand

    Joined: Oct 15, 2001
    Posts: 5371
    Originally posted by Jeff Mychasiw:
    FYI,
    These patterns are explained very well in the Book: EJB Design Patterns. You can find a PDF at www.theserverside.com

    Thanks for info..
    When I tried there 2 weeks back it said that it will be available soon. Thanks ..
    deneb shah
    Ranch Hand

    Joined: Feb 13, 2000
    Posts: 60
    Session Facade
    By meaning facade is some kind of an abstraction.
    Lets say that when you want to access the a number of entities. Say u r the teacher and u want to see the attendance of students, if u want to see any important notice on the notice board on the site and so on and so forth.
    you would create a facade so that that object calls all these entities and not you.
    It does the following
    - reduces network
    - helps maintain transaction across entities

    BusinessDelegate
    by definition a delegate refers to a representative. a business delegate is supposed to be a business representative.
    So if u have a business service available, u would create a business represntative on the presentation layer so that the presentation layer is independent of the business/service layer
    this
    - hides the complexity of an application to connect to the business systems
    - enables easy development since now the presentation layer can work independently of service layer
    - it can cache data thats on the server side so to as to decrease the round-trip
    Typically a sytem would be
    Servlet -- Action Object -- BusinessDelegate -- SessionFacade -- Entities -- Back-End system

    Some place where experience helps and certifications dont


    denice the menace
     
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