Service Locator and session facade pattern

What are differences between Service Locator and session facade pattern?
For me it seems one and the same.
Please explain me in detail. Expecting kind help.
Thanks,
Rahul
Edited by: rahulb1 on Feb 26, 2008 5:07 PM

rdoekes wrote:
The ServiceLocator Pattern is a singleton which hold a map of used DataSources. The idea is that you perform a lookup once and use the cache afterwards. The session facade is just one DataSource lookup.huh? Those J2EE patterns are not really reduced to datasources and the SessionFacade has actually nothing to do with datasources.
Session Facade
It has Facade in it and a Facade is usually used to give a simple entrypoint by providing a standartized interface. The same is now with the Session Facade. You have a Session bean that represents a high-level business component that interacts and calls lower-level business components.
Imagine having client a accessing 5 business objects with the remote calls, which is not an efficient way (network latency) or accessing the SessionFace and the session face is doing all the work through local access.
Service Locator
As J2EE components are using JDNI to lookup for ejb interfaces,DataSources, JMS components, connections etc. isntead of writing all the lookup in many code piecess across the project, you write a service locator that gives you a centralized place to handle the lookup's. It's easier to maintain and to control such a setup.
As you can see there's quite a big difference ;-)
cya,
Nail

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Business Delegate and Session Facade Pattern

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The only way to use the Session Facade Pattern, is if I use EJB for Persistence.
Is valid to do this?:
I use Ejb for simple update, insert querys. From my business delegate I call the Session Facade Layer, and from this I invoque Entyties for persistence.
But if I have complex querys, is correct to make PL SQL Procedures and do the following:
From my business delegate I call to the Dao layer, and from this via JDBC I call the Procedure.
Please explain me the best form to do this, having complex querys for reporting and simple querys for inserts/update.
Is valid to combine the use of CMP (for simple persistence cases), BMP (for complex persistence cases), and JDBC for complex select querys with multiple result rows.
Thanks!!

It depends on your design goals. One of the forces driving the use of patterns is the desire to tier an application and abstract the internals of each tier away from the other tiers. One (normal) benefit of this methodology is that the application should become more portable. Now, if you are using PL/SQL, BMP and CMP, you are mixing and matching portable versus proprietary. This is okay. But you should abstract away whether you are using PL/SQL, BMP or CMP from the business layer (or domain model). Ideally, you could completely swap database technologies (say from relational to object) and only have to re-write your integration tier (your DAO's).
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"My karma ran over your dogma." - Anon

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Does any one tell me, what is the difference between business delegate and session facade design patterns.

1. Session Facade decouples client code from Entity beans introducing session bean as a middle layer while Business Delegate decouples client code from EJB layer ( Session beans).
2. SF reduces network overhead while BD reduces maintenance overhead.
3. In SF any change in Session bean would make client code change.
While in DB client is totally separate from Session bean because BD layer insulate client from Session beans(EJB layer).
3. In only SF scenario, Client coder has to know about EJB programming but BD pattern no EJB specialization needed.
4.SF emphasizes on separation of Verb, Noun scenario while BD emphasizes on separation of client(presentable) and EJB layer.
Anybody pls suggest more differences ?

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Hi guys.
I am new to JavaEE and I recently learnt the Business Delegate and Session Facade design patterns. The tutorials from Oracle did gave me a basic idea of what they are and why they are used, but the example didn't really answer all my questions. So I decided to use a real life scenario here and put my question in to it. Any help is appreciated.
Assume I want to create a search employee page for my company, the employees are categorized by his or her department and the province he or she is in. I have in the database a look up table for department and province. (as shown in the image below)
http://oi46.tinypic.com/idvpsl.jpg
So I create three JPA entities, one for each table. Now I am stuck with what is the proper way to design the session facade design pattern. I know that I will need the to access all three entities in my page. (to get the drop down list for Provinces and Departments, and to retrieve list of Employees based on the selection) So should I create a Stateless Session Bean as session facade to access all three JPA Entities or should I create three separate Stateless Session Bean to manage one Entity each?
I came up three component diagram in the below picture.
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The second one has a session facade to manage the relationship between business objects such as ProvinceManagerEJB and DepartmentManagerEJB which will manage the corresponding Entities.
The last one has three Stateless Session Beans that will manage one Entity each, all three Stateless Session Beans can be looked up via the Business Delegate pattern.
http://oi46.tinypic.com/10pqets.jpg
Please let me know if any one of them is the proper way to use business delegate and session facade. or none of them is correct. (which I assume might happen)
Again, thank you so much for your help.
Cheers
Edited by: 992005 on 05-Mar-2013 18:15
Edited by: 992005 on 05-Mar-2013 18:17

Well I can't access any of your diagrams from here so can't comment on them. For dividing the functionality into separate classes, think about
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2.) Are you duplicating logic in the services? e.g save person, delete person in one service and save department, delete department in another e.t.c is better factored into one service with save entity, delete entity calls because the JPA entity manager doesn't know about the type anyway and it's easier to apply common logic (e.g logging auditing) around the calls.
3.) Will each service makes sense on it's own or do you always need the other functionality to completely describe the service? Here it is important not think about entities but about the business use cases. Process1Service is better than Entity1Service, Entity2Service ... EntitynService.Think granule of reuse = granule of release. Only split out individually reusable services. A good way to understand granules of reuse in your system is to think about (or start by writing) test cases for the functionality. Testable code is reusable code.
4.) Will the services change together? At class level you would look at common closure principle (classes that change together should be packaged together). You can apply the closure to the methods as well. Make it easy for future developers to recognize dependent functionality by packaging it together.
These are just general because in enterprise development requirements are king. You can chose to follow or discard any of these rules depending on your requirements as long you understand the impact of each decision.

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Hi, I've been programming with java for a long time now, but recently decided to formally studing the J2EE patterns. By now I have the intuition of many of them but in paper looks a little confusing. Let me ask you what is a clear diference between Business Delegate and Session Facade.
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What is the best way to allow the client to
interact
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If you are not using EJB or a distributed
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All,
Well this is the closet forum i could get to post my question so please excuse me if it is in wrong place.
Can anyone mention the types of facade design pattern available ? Also what is the diff between Facade and Session Facade ?
PS : My application is getting developed in ADF :)
thnks

in the line of fire wrote:
All,
Well this is the closet forum i could get to post my question so please excuse me if it is in wrong place.
Can anyone mention the types of facade design pattern available ? Also what is the diff between Facade and Session Facade ?This is no really ADF specific. You may wish to consult both the "Gang of Four" book along with Fowler's "Patterns of Enterprise Architecture."
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>
PS : My application is getting developed in ADF :)
thnks

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Could someone provide the key differences between these two patterns.
And one more, is Session Facade applicable(can be implemented) only to Enterprise Java Beans? Or even a POJO can be a Session Facade
Thanks in Advance

Business Delegate as well as Session Facade are used
to reduce coupling between presentation-tier clients
and business services.
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Message was edited by:
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Message was edited by:
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