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Learning resource for EJB

Shridhar Raghavan
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Joined: May 27, 2010
Posts: 71
Hi,

Am new to EJB. Looking for a resource that helps you understand EJB from a novice perspective. All i know currently is they are an architecture (pattern) that are used to write classes that can be accessed and executed remotely. Am i right?
Devaka Cooray
ExamLab Creator
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Joined: Jul 29, 2008
Posts: 3019
    
  35

Shridhar Raghavan wrote:that are used to write classes that can be accessed and executed remotely. Am i right?


That's not the purpose of EJB. An application server, in which the EJB components are running, usually provides many other services including concurrency management, pooling service, etc.. Basically it provides a tiered architecture for keeping the business logic separated from the other components of the application.


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Jimmy Clark
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Joined: Apr 16, 2008
Posts: 2187
Java Enterprise Edition:
Integrating JSF, EJB and JPA
Streamlining Enterprise Application Development
http://www.learningtree.com/courses/936.htm
Shridhar Raghavan
Ranch Hand

Joined: May 27, 2010
Posts: 71
An application server, in which the "EJB components" are running, usually provides many other services including concurrency management, pooling service, etc.

Hey,

Out here by "EJB components" you mean the classes that i would write which relate to business logic right? If that is so, then does the EJB architecture divided into follwoing tiers/includes
1. classes at the web tier that take care of application server responsibilities you mentioned above
2. classes at the application tier responsible for business logic. These classes would be things like beans and implement the remote and home interfaces.

Basically what i want to understand is when we use the term EJB components, do we mean classes written for business logic or we mean the "architecture" of a distributed application? Or have i completely missed the mark
Devaka Cooray
ExamLab Creator
Saloon Keeper

Joined: Jul 29, 2008
Posts: 3019
    
  35

Shridhar Raghavan wrote:1. classes at the web tier that take care of application server responsibilities you mentioned above

No that's not.

Shridhar Raghavan wrote:2. classes at the application tier responsible for business logic. These classes would be things like beans and implement the remote and home interfaces.

Yep!

EJB components are the enterprise Java beans deployed in the EJB container. These could be session beans, message driven beans, singleton beans, etc... EJB is not related to the classes you write in the web tier. Perhaps, the classes in the web tier may access the EJB components in the application tier. However, EJB is not only for web based applications - you can have your business logic on the business tier and access that application server from any other component in the front tier - for instance, from a swing application. So basically you can't include web tier components when defining the concept of EJB architecture. Also note that EJB architecture is a multi-tier / multi-layer architecture, but that doesn't required to be in the distributed architecture.
 
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subject: Learning resource for EJB
 
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