Business Delegate Design Pattern

[KRK Gowda]

Hi All,
I had a question in a mock which reads :
Business Delegate facilitates JSP to communicate with EJBs. is it true or false.

Answer is True.

i am confused.

please explain how it is possible.


Thnks and Regards,

[Celinio Fernandes]

why are you confused ?

[KRK Gowda]

I am confused on how JSP can communicate with EJB through Business Delegate

[Prabhu Venkatachalam]

used to reduce coupling between Web and EJB tiers.

All the request from Web tier to EJB tier goes through Buisness Delegate, So that, if something changes in EJB Tier will not affect Web Tier and vice versa.

Normally, For an application J2EE design pattern flow will be something like,

---> Service Locator
|
Client --> Front Controller --> Business Delegate --|
|
|
----> Session Facade


In the above figure, If you see all the interaction between VIEW(JSP) to Business Tier(EJB tier) goes through Business Delegate.

hth,

[Prabhu Venkatachalam]

Sorry, figure got messed up.

used to reduce coupling between Web and EJB tiers.

All the request from Web tier to EJB tier goes through Buisness Delegate, So that, if something changes in EJB Tier will not affect Web Tier and vice versa.

Normally, For an application J2EE design pattern flow will be something like,




In the above figure, If you see all the interaction between VIEW(JSP) to Business Tier(EJB tier) goes through Business Delegate.

hth,

[Prabhu Venkatachalam]

Again

    
 
                                                     ---> Service Locator
                                                    |
Client --> Front Controller --> Business Delegate --|
                                                    |
                                                    |
                                                     ---->Session Facade
 

[navat venu]

yes,J2EE clients(JSPs) interact with service components, such as Enterprise JavaBeans (EJB) which provide business services ,through Business Delegate .Business Delegate uses service locator to locate these business services .

[Marc Peabody]

Other than perhaps for retrieving a collection for populating a select dropdown box, a JSP should not be making any calls to the back end. Calls to the back end are typically business-related and belong in the controller classes.

[KRK Gowda]

Thnx Marc for your reply

[navat venu]

Other than perhaps for retrieving a collection for populating a select dropdown box, a JSP should not be making any calls to the back end. Calls to the back end are typically business-related and belong in the controller classes

Hi Marc,
Normally we do retrieve a collection for populating a select dropdown box in the "load-on-startup" servlet itself and do data caching in memory(Application variables),so that call to backend is done only once at the application startup and further, jsps which have dropdown box will retrieve the collection from memory rather than making calls to backend every time.

correct me if i am wrong!!