EJB or not EJB?

Question

Hi all,
I am fairly new to J2EE, and have recently been reading up on it, checking out the blueprints and the tutorials.
I have recently finished a web app based on Microsoft technology (ASP and COM+), and we now wish to rewrite it the J2EE way.
My dilema is that I cannot decide if I need to use EJB's, or if the application really warrants it. I could easily just build it in the Web container using JSP, Servlets and JavaBeans.
Basically, the app. is just a glorified tool for clients to browse/search through a very large database (45 million entries). We have lots of behind the scenes functionality to provide page level access control that interfaces with a legacy CICS server, but essentially that about it. The majority of the front end will be implemented in applets.
Any guidance would be gratefully received.

Answer 1

As per my recommendation you should use EJB in your application because of the following factors:-
1. You can separate the presentation logic, business logic and the data persistence logic of your application using EJB.
2. For presentation always use JSP ,unless it is applet.It should contain least(not none) java code.
3. The EJBs should be used for business logic and persistence logic. EJBs are broadly of 2 types i.e. Session beans and Entity Beans. Use Session beans for workflow management and Entity Beans for persistence management. Keep in mind that it is useful to use Enity beans only if reusability of the database access logic is required. Non reusable database logic can be coded in Session beans as using in it Entity beans will result in unwanted overheads.
4. You can easily manage transactions using EJB, just by making a simple entry in the XML deployment desciptor.To accomplish this using JSP/Servlet you need to use java transactions API(UserTransaction and all).
5. You donot need to write the database access logic in case of CMP entity beans.
6. Container manages synchronisation of the data in the entity bean and the data in the database, thus it ensures that you always get latest data from the database. The synchronised is taken care by the callback methods defined in the EntityBean interface.
7. In case of entity beans perfomance is optimised since Container is handling complex things like maintaining the pool of instances of Stateless Session beans and Entity Beans. The instances are swapped between different EJB object as and when required by the container. Also the instances are returned to the instance pool once they have been used.
I feel that these few points can help you.