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Tiers in J2EE framework

 
vikasids sharma
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please let me know the concept of TIERS in J2EE
Is it a logical boundary or a physical boundary between layers.
When i have webserver,application server and database server on same machine
Is it a single tier or three tier?
thanks
Vikas
 
Anonymous
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Hi Vikasids
The tier model is the logical dividing of the three logical functions: presentation, business logic and data storage. Even when you are having it all on a single server, it will be possible to make a nice three tier model.
BR Jan
 
Matthew Phillips
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A tier is generally a logical boundary, but a physical boundary could exist as well. For example, my servlets and jsps may represent a web tier of my application. My EJBs representing my business logic are the 2nd tier, and my database is my third tier.
It doesn't really matter where my servers are running, you still have the logical separation of your code. If they are running on separate servers, then you have a physical boundary that maps to the logical boundary.
 
Pradeep bhatt
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Q- Do Stored procedure and table data exist in different tier.?
I remember reading a article which tells me SP are in a different tier than the database data. SP is in data access tier and data is in data tier.
 
Lasse Koskela
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Physically you can't separate stored procedures and the data as both are located in the database server (stored procedures are "installed" into the database similarly as records are inserted). Logically, however, the stored procedures belong to the business logic layer (or, if you prefer separating even more, to the data access layer).
 
Stan James
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There are many ways to look at tiers or layering. I collected a few on my Logical View andArchitectural Layering pages.
 
vikasids sharma
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From the above clarifications can i make out one thing for sure that
Tier architecture expands from n tier to n+1 in both horizontal and vertical directions.
Lets say
We have 3 separate layers(tiers) for respective presentation , business and data base related data
case 1
if we break business layer in further two layers , we will call it n tier(3+1)solution.(vertical expansion)
case 2
if we add another layer horizontally to presentation, business and database , again we will call it n tier(3+1) solution.
 
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