Business Delegate, Session Facade or both?

Hi,
I'm having some problems with figuring out the point of using both Business Delegate (BD) and Session Facade (SF). As far as I can see, you often have a 1-1 mapping between the BD and SF, so why not use the SF directly?
Here's my scenario. I have a web application that uses WebWork for presentation and pageflow, a session facade implemented using an ejb, which aggregates calls to the businness objects into "business rule"-methods and business objects implemented using plain java objects. Is there really any need to have a business delegate here? I might as well use the session facade directly from the webwork actions? Or..?
Any suggestions? Am I far off? ;-)

As far as I can see, you often have a 1-1 mapping between the BD and SF, so why not use the SFYou can have one Business Delegate encapsulate all of the business methods that are exposed by one or more Session Facades. The benefit here is that you protect the web component from any details of the business tier. e.g. your business tier has five session facades and the web tier has a single Business Delegate. The BD can be extended to call web services as well.
Here's my scenario. I have a web application that uses
WebWork for presentation and pageflow, a session
facade implemented using an ejb, which aggregates
calls to the businness objects into "business
rule"-methods and business objects implemented using
plain java objects. Say you eliminate the EJB implementation. What effect will this have on the web tier objects? The Business Delegate will enable you to easily replace the business implementation with little impact on the web components.

Similar Messages

Business Delegate & Session Facade

1 What is the need of Business delegate? For controlling the interactions between the presentation tier and business tier, session facade pattern can be used.
2 Can a session facade have all the facade related methods. (i.e. entire application has only one session facade). In the pattern documentation, it is stated as this stratergy inefficient. Why is so?

1 What is the need of Business delegate? The delegate provides a client-side business abstraction and acts as a proxy for the business service. Note that it is a proxy, not a facade. In other words, it is a "stand-in" for the biz service, but it is not aggregating several method invocations into one and controlling the processing flow. So, the delegate is not providing a higher-level interface to some underlying system, as would a facade.
So what's the need, if it's just a proxy? Obviously, it adds a layer, so one must consider its benefits versus the drawback of writing, maintaining, and interacting with this extra layer. In a sophisticated system, the benefits are many and will usually outweigh the drawbacks. Following are some of the benefits of using a delegate in the web container as an access point for invocations to the business tier:
- It hides the underlying implementation details of the business service (ie: lookup, creation, access details of EJB...The delegate may use the Service Locator pattern to achieve this goal).
- The delegate translates exceptions as necessary. Service-level exceptions, such as java.rmi.Remote can be intercepted by the delegate and translated into application exceptions. This also helps shield web container clients, for example, from EJB and network-related implementation details, which they should not need to worry about.
- The delegate can attempt retries/recovery efforts transparent to its clients, such that this code can be localized and reused, instead of being duplicated in numerous clients.
- The delegate can also manage a cache of resources/results, limiting unecessary remote roundtrips
- The delegate can be used as a control point for multi-threaded access into the business tier. For example, stateful beans are not to be invoked by multiple client threads simultaneously. The delegate can serialize access, or, as mentioned above, handle exceptions/retries, as necessary.
For
controlling the interactions between the presentation
tier and business tier, session facade pattern can be
used.If you decide to use a delegate in your system, based on considering its benefits, as described above, then you'll typically create a one-to-one mapping between a delegate and a session facade. The delegate is not controlling the processing flow per se, but rather serving as a single access point and proxy as described above. The facade acts as a controller, though, aggregating the interfaces of underlying components and subsystems into a higher-level interface. If you find that your using the delegate more as a facade, we recommend pushing this control code from the web container (where the delegate lives) back to the session bean in the ejb container, so that the logic can be reused across clients.
>
2 Can a session facade have all the facade related
methods. (i.e. entire application has only one session
facade). In the pattern documentation, it is stated
as this stratergy inefficient. Why is so?Having a single facade for the entire system would prove to be quite a maintenance and manageability headache for a non-trivial application. Imagine that every time something changes in any subsystem of the service layer, developers are all making changes to the same file and the same class...Not desirable and not very elegant. At the same time, one does not want to go the other way and create too many facades by having a one-to-one mapping of session facades to use cases, for example. We recommend aggregating a group of related interactions into a session facade, so that it provides highly course-grained access and control to underlying components.
Thanks,
Dan

Business Delegate / Session Facade interaction questions

I understand the concept and the benefits of a business delegate "front-ending" a session facade. I am hoping that someone can answer the following questions:
Is it acceptable if a business delegate were to front-end more than one session facade in order to create a more unified service. For example is it ok to create one business delegate that provides Account Inquiry and Maintenance functionality and behind the scenes it talks to an AccounInquiry Session Facade and AccountMaintenance Session Facade?
We are looking at a designing a Account Inquiry business delegate. It will return an AccountProfile business object. A behaviour of the AccountProfile object will be update capability (i.e. update account status, modify balance, etc.). Considering that the business object is a "business tier" component, is it ok fif it were to talk directly to an Account Update Session Facade or instead should it use a business delegate which in turn will call the session facade?

I understand the concept and the benefits of a
business delegate "front-ending" a session facade. I
am hoping that someone can answer the following
questions:
Is it acceptable if a business delegate were to
front-end more than one session facade in order to
create a more unified service. For example is it ok to
create one business delegate that provides Account
Inquiry and Maintenance functionality and behind the
scenes it talks to an AccounInquiry Session Facade and
AccountMaintenance Session Facade? This is a feasible solution. As long as you have 1:2 ratio or a ratio which is very less, it is fine. But one of the intents for having this pattern is also to make the client's life easier. If the client who's using your delegate is someone else, sitting else where, he/she would be wondering about the reason for a single class like AccountInquiryMaintenanceDelegate providing two different functionalities. So, this has to be kept in mind before coming up with a single class.
We are looking at a designing a Account Inquiry
business delegate. It will return an AccountProfile
business object. A behaviour of the AccountProfile
object will be update capability (i.e. update account
status, modify balance, etc.). Considering that the
business object is a "business tier" component, is it
ok fif "it"what does "it" mean here?? Did you mean the 'AccountProfile' bussiness object?? or the AccountInquiry business delegate??
were to talk directly to an Account Update
Session Facade or instead should it use a business
delegate which in turn will call the session facade?
HTH,
Kalyan

Bussines Delegate -- Session Facade

Hi,
My design is:
client --> bussines delegate --> session facade ---> application service --> dao
........................................................................................................|
........................................................................................................|
......................................................................................................pojo
I have 2 session facade: PurchaseManagement and InventoryManagement.
I have a use case that need access to services provided by both session facade.
Which is the best solution?
1- Define a bussines delegate for each session facade and the client use both bussines delegate
2- Define a unique bussiness delegate that access to both session facade
3- ????
Thanks.

I have 2 session facade: PurchaseManagement and
and InventoryManagement.
I have a use case that need access to services
ces provided by both session facade.
Which is the best solution?
1- Define a bussines delegate for each session
ion facade and the client use both bussines delegate
2- Define a unique bussiness delegate that access
ess to both session facade
3- ????If you are using a client-side Business Delegate, you do not need a one-to-one mapping to each Session Facade. The single Business Delegate should be composed of business methods from both Session facades. This will help keep the application modular. If you ever decide to change the design of the business tier, nothing will have to be changed in the presentation tier.
Best,
Sam
http://www.softwareleadership.org/docs/overview_UW_RPM.html

Session Facade and Business Delegate Pattern

Hi!
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!!

The session facade is borrowed from the facade pattern, so you could have a facade to almost anything.
A session facade is usually against other beans...for example if you
(Not deployed as CMR)
1. Address bean
2. Phone Bean
3. Customer bean
as entity beans then you can build a session facade such as
CustomerFacadeBean which will CreateReadUpdateDelete(CRUD) address and phone as well when a customer is CRUD ed.
In your case you said you have very complex sql's so one way would be
Business Delegate -> Session Facade -> (Bean Managed) Entity Bean -> DataAccessObject.
If you think this is a overkill then, write a custom pattern such as DataDelegate
DataDelegate -> (Bean Managed) Entity Bean -> DataAccessObject.
In the above scenario you should be quite sure that the system will not evolve into a case mentioned above such as when customer is deleted a phone and address object are also thrown away.
You said this scenario
Business Delegate -> DAO..
I don't think this is a good idea because, a business delegate is a proxy against business objects....and usualy in J2EE business objects are session beans. Entity and DAO objects are data objects not business ones.
Besides if you do the above scenario you will end up wiring all the transactions, etc etc in your DAO which is not a good idea.
Although you could use BusinesDelegates against entity beans it will lead to a misnomer.

Difference between session facade and business delegate patterns

Hi,
How the session facade and business delegate patterns differ from each other, as both of them have similar and almost same forces to be addressed.
Please address.
Satya.

BTW, in J2EE Core patterns :
When the Business Delegate is udes with a Session Facade, typically there is a one-to-one relationship between the two. This one-to-one relationship exists because logic that might have been encapsulated in a Business Delegate relating to its interaction with multiple business services (creating a one-to-many relationship) will often be factored back into a Session Facade.[I/]

=== SESSION FACADE v/s BUSINESS DELEGATE ===

Hi
Can anyone help me with my design here - I am not sure whether to use a Session Facade or a Business Delegate in the following scenario:
[Our application is pure J2EE and does not use EJBs]
PRESENTATION-TIER
I have a Command and Control strategy employed in my presentation tier where requests are intercepted by a controller and processed by helpers delegating to appropriate commands and dispatch appropriate responses.
PRESENTATION-TIER - COMMANDS
The Commands will invoke appropriate Business Methods in the business tier to retrieve data (mostly).
BUSINESS-TIER
Now - most of my business methods use the DAO pattern to retrieve data and are effectively dealing with Data Beans (Value Object beans) - passing them back to commands.
I can clearly see the use of a generic Interface at the Business tier - i.e., rather than expose the Buiness Methods direcly leading to increased coupling between presentation and business tiers.
BUT THE CONFUSING PART IS - DO I USE A SESSION FACADE OR A BUSINESS DELEGATE TO INTERFACE WITH MY COMMANDS??? What is the difference? I have looked at Sun's J2EE blueprint and cant make out the clear cut difference between the two.
Can anyone help?
thanks
Aswin

I agree with you, Business delegate and Session facade are quite alike.
I believe that you could use the Business delegate pattern as a facade. Possibly, you could argue that the Business delegate is an extension of the Session facade pattern. However, I think that SUN thinks that a Business delegate should be a singleton while a Session facade is a session EJB. My firm belief is that you could create a business delegate that is a session EJB instead.
But, you could also use both pattern as some one else suggested.
In your case when you do not use EJBs, I would suggest that you use a facade which could be design like a business delegate. However, as there aren't any EJBs, you will not need a service locator. In this way, you will have a design that can be extended (without any impact on the the presentation tier) to use EJBs in the future.
Remember, SUN's core J2EE patterns assume that you use EJBs. If you don't, they have to be adapter a little bit.

Business Delegate and Session Facade

Business Delegate as well as Session Facade are used to reduce coupling between presentation-tier clients and business services.
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.
Yes. And also in EJB to overcome some of the deficiencies in distributed architectures.
Could someone provide the key differences between
these two patterns.
Business Delegate is used by a client whereas the Session Facade is used to abstract a business service.
And one more, is Session Facade applicable(can be
implemented) only to Enterprise Java Beans? Or even a
POJO can be a Session Facade
Yes. Think of a session facade as your 'easy' or 'high-level' API. Your actual business tier may have its own 'low-level' API that callers should not have to interact with or understand.
Thanks in AdvanceYou're welcome.
- Saish

Business delegate and Session facade design patterns

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 ?

Business Delegate and Session Facade Pattern

Hi!
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).
Session facade is simply a glorified Facade pattern. It abstracts the lower-level details of what you are persisting and instead forces you to think in terms of objects. You can use a facade without even remotely touching EJB's. It just so happens that, historically, EJB containers made a mess out of scalability when it came to entity beans. The "session" facade refers to a facade pattern implemented in session beans (that have fewer scalability problems) communicating with the entity beans which do have scalability problems.
So... to make a long story short, use whatever persistence mechanism you desire. Remember that you should be able to completely switch your persistent store from one type or another and simply re-write your DAO's (or CMP deployment descriptors). Using a facade pattern can help towards this end, but don't make it a straightjacket.
- Saish
"My karma ran over your dogma." - Anon

Business Delegate and Session Facade usage.

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.
The first one has one Stateless Session Bean as session facade and manages all three Entities.
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
1.) Quantity - Are there many enough service calls to require splitting up or will one application service class be enough? The size of the system is important here.
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.

Difference between Session Facade and Business Delegate??

Hello,
I am currently working on design patterns and I am confused what the difference is between the Session Facade and Business Delegate pattern. They look identical.
What's the difference?
Balteo.

We implement Business Delegators (BD) as follows:
1. The client always talks to the BD.
2. The BD then talks to either our Session Facade, Session EJB, or Java Class, etc, etc directly.
This allows the client end code to never change whilst allowing our BD to swap between different providers of the service we require.
It's the good 'ole "layer of indirection" thingy.

Difference between Session Facade and Business Delegate design patterns

Can someone tell me the differences between Session Facade and Business Delegate 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 ?

Diferences between Business Delegate and Session Facade

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.
For me, exposing interfaces, hiding implementations and masking the complex interactions in the back are common factors in these patterns, could you please help me to identify diferences?

There are more subtle differences, but the basic gyst is that the Business Delegate is used on the client/presentation tier. The Session Facade is used on the server/service tier. The Business Delegate typically performs a lookup of the SessionFacade which in turn fronts a service method (EJB or otherwise). The Business Delegate pattern is typically associated with J2EE remoting and its shortcomings.
- Saish

Bussiness Delegate vs Session Facade.

Hi,
Please any one tell me what are the differences between Bussiness Delegate and Session Facade.
I read some documentation in online but not clear in above two design patterns.
Any help I will appricate.
Thanks,
CDulla.

A business delegate is generally thought of as a plug-in that is given to the client developer. This "plug-in" can do service lookups and searches on behalf of the client developer. Very smart if you have a Swing or Servlet Developer that doesn't know ejbs.
A session facade is a session bean that is much like the delegate but resides on the server and is used to encapsulate course services so that network can be held to a minimum.
A business-delegate can call a session facade which in turn can call an entity bean

Business Delegate, Session Facade or both?

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