DTO/TO - Which Tier??

[A J Kumar]

Hi,

I am planning to group my components in various package based on the tiers. However I am not sure where does all the DTO/VO belongs. EJB Tier or EIS Interation tier.

Thanks,
AJ

[Ramon Gill]

Perhaps you could show them in an 'integration' tier between EJB and EIS ?

Ray

[A J Kumar]

Thanks Ramon. I got it.

The Core J2EE Patterns book shows DTO in business tier. I think I am gonna rename the tier name to Client, Presentation, Business and integration tier instead of Web, EJB and EIS tier. That way its more generalized and not confined to a particular technology.

Can the certified SCEAs please comment on that.

AJ

[Dhiren Joshi]

Kumar,
What notation are u going to be using on your component diagram to depict the different tier.
Also how are you going to manage inter tier component interactions. Which modeling tool are you using.

Thanks
Dhiren

[A J Kumar]

Dhiren,

I am using Rational rose. And currently I am using package notification to group the components. However I haven't seen any document or book that actually does that, but some SCEAs have successfully used package notification in the past.

The Core J2EE patterns book uses vertical lines to depict the tiers. I would prefer to use the vertical lines instead of packages, however I could't find the option to draw vertical lines in the component diagram using rational rose enterprise edition. I know it can be done in visio. Can some one help me with this.


AJ

[Dhiren Joshi]

Thanks Kumar for your reply.
I think James also went with package notation and got full marks in his component diagram.
I was not sure if tiers could be represented as packages.
best for to be SCEA's would be use the package notation instead of the vertical lines as I have seen SCEA get full marks on that.
At least now I am convinced to use the package notation and I found that Rose can support inter tier package wonder why it wasnt working before for me.

Thanks
Dhiren

[Parag Doshi]

Originally posted by Dhiren Joshi:
Thanks Kumar for your reply.
I think James also went with package notation and got full marks in his component diagram.
I was not sure if tiers could be represented as packages.
best for to be SCEA's would be use the package notation instead of the vertical lines as I have seen SCEA get full marks on that.
At least now I am convinced to use the package notation and I found that Rose can support inter tier package wonder why it wasnt working before for me.

Thanks
Dhiren

Just to understand it correctly, you'll are gonna create 4 gigantic packages and name them as client, web, business and EIS? And then put all the related components in each tier?
And a related question, which tier do you show the ServiceLocator in? web or business or both?


Parag
[ October 11, 2004: Message edited by: Parag Doshi ]

[Dhiren Joshi]

Parag ,
I will have one extra package on the client in addition for the travel agent components.
Its not looking so gigantic as I am adding smaller details only in notes and not showing all the components like all every DTO/TO. Also not showing all action and event components just adding a note to elaborate.
ServiceLocator I will add to Web as I think it goes with the EJB controller component. Does any one one have any suggestions .

Thanks
Dhiren

[Parag Doshi]

Originally posted by Dhiren Joshi:
Parag ,
I will have one extra package on the client in addition for the travel agent components.
Its not looking so gigantic as I am adding smaller details only in notes and not showing all the components like all every DTO/TO. Also not showing all action and event components just adding a note to elaborate.
ServiceLocator I will add to Web as I think it goes with the EJB controller component. Does any one one have any suggestions .

Thanks
Dhiren

I just had one question: Do we require Service Locator for locating local entity beans on the business tier?

Parag

[A J Kumar]

Parag,

You will need Service Locator to lookup the local EJBs. The service locator for the EJB tier will be different from the service locator for the web tier in the following two respects:

1. You don't need to use PortableRemoteObject.narrow for the ejb-tier service locator, since the local entity beans are in the same JVM as Session Facade.

2. You can implement caching mechanism in the web-tier service locator, which is not required for the ejb-tier service locator.

HTH
AJ

[Parag Doshi]

Originally posted by A J Kumar:
Parag,

You will need Service Locator to lookup the local EJBs. The service locator for the EJB tier will be different from the service locator for the web tier in the following two respects:

1. You don't need to use PortableRemoteObject.narrow for the ejb-tier service locator, since the local entity beans are in the same JVM as Session Facade.

2. You can implement caching mechanism in the web-tier service locator, which is not required for the ejb-tier service locator.

HTH
AJ

AJ,
Why wont I need caching mechanism in my ejb-tier service locator?

Parag
[ October 12, 2004: Message edited by: Parag Doshi ]

[Annie Zhang]

If Service Locators are shown for the local EJBs, wouldn't that too detailed? I guess just showing session (entity) facade to call those local EJBs is enough for the assignment.

As far as I know from the petstore, the service locator, business delegate, value object, EJB controller are the bridge btw the web and the business tier. Although they are more related to the web tier, I am wondering if it is a good idea to show the "bridges" besides the 4 "gigantic" packages/subsystems.

[Dhiren Joshi]

Yes Annie I agree that the service locator in the web tier is an important component as that is a bridge between the event action of EJB to business and this needs to be shown in the component diagram.The service locator in the business tier locally used can be indicated with notes as Annie has pointed out.
I will go with that strategy.
Thanks Annie.
Dhiren

[Parag Doshi]

I have only shown the depedencies of the business delegate (in my component diagram) on the SL as it needs to find the right facade session bean to talk to. (I havent followed the petstore implementation). I havent shown the facade dependency with the SL for finding other service ejbs and entity beans etc..I have added it as a note and in my supporting doc.

Parag