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Can we have a deployment Descriptor in EJB 3.x

I am trying to narrow down the major changes in in EJB 3 and EJB 2, and noted the following changes
EJB 3.X does not required a deployment descriptor; does this mean we can not have a deployment descriptor ?
Also the home and the remote interfaces ? does this mean we can not implement any the aforementioned interfaces in EJB 3.x. Can someone explain what are the main use of Home and the remote interfaces in EJB 2.x
EJB 2.x does not use or implement POJOs , can some one explain the exact use of POJOs in EJB 3.x, with a minor example
I have covered EJB 3, yet I do not have any knowledge in EJB 2.x
Regards
Rashendra

ad 1/ One can certainly have explicit XML-based deployment descriptor with EJB 3.0. However, as compared with 2.x, it is not anymore obligatory to have one. One uses explicit XML deployment descriptor when some of the settings specified on Java class itselfs needs to be augmented.
ad 2/ There is an remote/local bean interface with EJB 3.0, obligatory with remote beans and optional with local beans. There is no home interface in 3.x anymore, which was used to manage the live cycle of entity beans (read:data) and session beans in 2.x. As the entity beans have been replaced by JPA and the life cycle management of session beans has been removed from the client code written by application developer, there is no need for home interface anymore.
ad 3/ Have a look at Java EE tutorial, it covers this well and there are certainly examples.

How to use MVC in Java EE 6/7 without using other frameworks?

I have already implemented the MVC pattern using the Spring framework.
In Spring there are #Controller and #RequestMapping annotations in the controller class and this framework doesn't use any HttpServlet.
I want this exact structure in Java EE (but without using any other framework).
So my question is: how can I use MVC in Java EE without using other frameworks?
Note: I don't want to use HttpServlet class

(1)
You can use JAX-RS and CDI to respond to HTTP requests, using annotations such as #Path and #RequestScoped. You might need some JAX-RS extensions or utilities for convenience, for better handling of parameters (e.g. RestEasy's #Form) and forwards to views (e.g. Jersey's Viewable).
(2)
You can also write a single HttpServlet (I hope that's not a problem) that will act as a front controller, instantiating the controller for each request. Using CDI, you can annotate your controllers with #Model (which is the same as #RequestScoped and #Named), and instantiate them in your front controller with:
#Inject #Any
private Instance<ControllerBaseClass> controllerInstance;
(...)
ControllerBaseClass controller = controllerInstance.select(«something»).get();
controller.processRequest(); // or execute() or anything you want.
request.getRequestDispatcher(«page»).forward(request, response); // or a redirect if it's a destructive operation.
What do you need to pass to select(«something»)? You can select an instance in CDI using annotation literals (consult CDI documentation) or classes (Class.forName(...)), depending on the request parameters.
Using CDI you can also make your controllers #ApplicationScoped instead of #RequestScoped.
As you see, you may need to build some infrastructure and stick to some patterns from then on, but it's perfectly feasible. I have used a mix of both strategies in a personal project and it works fine.

You can do it with technologies available in Java EE.
It's important to mention that Java EE is itself composed of many specifications/frameworks, for which there are more implementations. See this: https://java.net/projects/javaee-spec/pages/Home
Example with JSF http://www.tutorialspoint.com/jsf/jsf_architecture.htm
Example with JSP http://www.datadisk.co.uk/html_docs/jsp/jsp_mvc_tutorial.htm
Another example with JAX-RS https://jersey.java.net/documentation/latest/mvc.html
JSF is much more feature rich than JSP, and there are many components already made for it: Omnifaces, Primefaces etc. JAX-RS is for web services.
Have fun!

By simply using EJB for business logic, CDI for bean management and JSF for view.

It is incorrect to say that with Spring MVC there is no HttpServlet. From Spring Framework javadoc : DispatcherServlet (a subclass of HttpServlet) is the Central dispatcher for HTTP request handlers/controllers of the Spring framework. So it's hidden in the framework but present.
In fact, except in JSP only applications (not really MVC ... and JSP are translated in ... Servlets !) or JSF applications, you have (subclasses of) HttpServlet in all Java EE applications. And as JSF is only a specification you have to use an implemantation of JSF. There are 2 well known implementations, Oracle Mojarra or Apache MyFaces but both are ... frameworks.
Of course, you can do MVC in Java EE without any framework. As explained in Model View Component on Wikipedia MVC is a design patter independant of any of its implementations. The hard part will be no HttpServlet.

EJB injections vs only JSF managed beans

I don't know may be my question is completely meaningless, but I can't find any straight information about it.
I had my JSF + Tomcat application and it worked just fine. I want to implement Restful services and JAAS logic. In order to do that, I switched to TomEE++.
Switching to TomEE means that my server will now be more heavy and I'm afraid than it will require more cpu and ram resources than I have in my Amazon AWS micro instance.
The question is: Will the performance drop down if I switch from only JSF managed beans to JSF + EJB?
The sub-question is: what EJB injections can do, and JSF managed beans can not do? (JSF does not allow cyclic injections for example)

Will the performance drop down if I switch from only JSF managed beans to JSF + EJB?
Measuring is knowing. But generally, this concern makes no sense.
what EJB injections can do, and JSF managed beans can not do? (JSF does not allow cyclic injections for example)
Generally, they are not intented to be interchangeable. Each have their own clear responsibility. You use JSF bean management annotations to manage beans for front-end (JSF pages). You use EJB bean management annotations to manage beans for business services (BOs/DAOs). That's it.
To learn how JSF+EJB(+JPA) are supposed to work together head to the concrete examples and explanations shown in the following answers:
JSF Service Layer
JSF managed-bean EJB injection
Filter do not initialize EntityManager
JSF request scoped bean keeps recreating new Stateful session beans on every request?

CDI and EJB, security issues?

I am reviewing my code from since I picked up on JSF.
One of the most complex issues has come up once again. The decision between CDI and EJB.
I am using three layers and I wonder which type of annotation to use on each of them:
- Backing beans (the Controller as defined in MVC)
- The service layer
- DAO's
My backing beans are using CDI, as long as I don't need anything from EJB.
But I am stuck on those other two. I remember reading about using EJB beans because of the pooling functionalities, which would prevent massive loads of requests (or attacks, if you will).
So in short, is there ANY reason to use EJB (Stateless, Stateful, LocalBean et cetera), considering security or anything else (excluded ViewScoped)?
Thanks in advance.

You're making a conceptual mistake here. CDI is absolutely not an alternative to EJB. CDI in its default trim doesn't offer transaction management at all. CDI is a bean management and dependency injection API, not a service layer API. In order to manage transactions in CDI, you've to add another API along with a bunch of another annotations.
CDI can replace for example JSF managed bean annotations, but definitely not EJB annotations.
So there's no means of a valid "CDI vs EJB" question. Both have their own completely distinct purposes. Note that you can perfectly inject EJB based service classes in CDI based managed bean classes.
As to security, it's not clear why you mentioned that part in the title and the tags, but the decision between CDI and EJB has nothing to do with security (simply because there's no means of a valid "CDI vs EJB" question in first place).

Yes when you require out-of-box support for transactions, concurrency, pooling etc.

Adding rest service to a struts application

I'm trying to add rest services to a struts application using jersey.For this i need to segregate the java code in such a way that it can be commonly accessed by both the struts and rest api.This is done so that the code is shared between both rest and struts,and any change will reflect in both the services.I would like to know , how much of this idea is feasible and weather this is how usually people design rest services .

While our presentation layer isn't Struts based (usually it's either Spring Web MVC or JSF), we use Spring 3.0 + Java EE 6, specifically, EJB 3.0 and JPA 2.0 for such situations.
EJB 3.0 stateless session beans work great—they can have declarative (annotation-based) dependency injection and transaction demarcation, or they can manage their transactions, dependencies and resources themselves using whatever traditional mechanism. They seamless integrate with JPA 2.0 and are easy enough to unit test. The main advantage over pure Spring beans is that they can be deployed independently of the Web application (as an EJB JAR).
On the front-facing Web services, we also use Jersey/JAX-RS. Because Jersey/JAX-RS dependency injection is broken (it doesn't use Weld/CDI like the rest of Java EE), we've had to resort to Spring DI to 'wire' up the front-facing REST resource classes with the 'back-end' EJBs. The good thing is this works well enough to inject the EJBs into our MVC controllers and can also be used with JSF managed beans. Alternatively, you can write your REST-ful resources using Spring alone (either way has its own pros/cons, but in general both do the job well).
I know I glossed over the whole thing but I'd be glad to share more details upon request.
EDIT: Some more details, as per request.
You're first stop for learning Jersey/JAX-RS would have to be the Jersey User Guide. There are also several tutorials/examples you can easily find across the 'Net.
While you should be able to package Jersey/JAX-RS resources into the same WAR as your Struts pages, we went with the simpler alternative of deploying them separately.
Now, when deploying to Glassfish 3.1, we hit this bug, also documented here. The bottom line is that #EJB injection didn't work for us as expected.
So, instead, we fell back on to Spring using the jersey-spring contrib module, following this example.
Anyway, the rest of it is standard Java EE 6 / EJB 3.0. We identify and place all common functionality into a 'service' layer which are largely implemented as #Stateless EJBs.
Persistence is handled through JPA #Entitys accessed through a JPA inject EntityManager. Transactions are declaratively demarcated using #TransactionAttribute.
Here's a quick illustration of a typical EJB + JPA service bean:
#Stateless
public class WidgetServiceBean implements WidgetService {
#PersistenceContext
private EntityManager em;
#Override
public List<Widget> findWidgetByName(String name) {
return em.createNamedQuery("Widget.findByName", Widget.class)
.setParam("name", name).getResultList();
}
#Override
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public void removeWidgetById(int id) {
em.find(Widget.class, id).remove();
}
}
(Obviously not production quality but just shows how 'lean' they can be.)
The service layer and entities are packaged as an EJB JAR which can be deployed separately, and made available to all other modules via global JNDI lookup. Or, they can be deployed within the Struts or JAX-RS WAR and as of Java EE 6 (Glassfish 3.x) they will be found, deployed as part of the module and made available to other components within the same WAR.
Some might argue that it's simpler to just use Spring beans if you're using the Spring container anyway. I would say, probably, but then you also have to use Spring's persistence framework, and Spring's transaction framework. (Spring also provides declarative transactions and persistence.) If you're already heavily invested into Spring then that might be an easier path.
OTOH, EJB 3.0, JPA 2.0 and JTA have also been radically simplified from their predecessors and are part of the Java EE standard so it's an architectural decision with a lot of dimensions.