Set - 3

Question 11 :

What is lazy loading?

Answer :

Lazy loading means not creating an object until the first time it is accessed. Lazy loading typically looks like this:
public class Example {
private Vector data = null;
public Vector getData() {
if (this.data == null) {
this.data = new Vector();
// Load data into vector …
}
return this.data;
}
}
This technique is most useful when you have large hierarchies of objects (such as a product catalog). You can lazy-load subordinate objects as you navigate down the hierarchy, and thereby only create objects when you need them.


Question 12 :

Can i map more than one table in a CMP?

Answer :

No, you cannot map more than one table to a single CMP Entity Bean. CMP has been, in fact, designed to map a single table.


Question 13 :

Is Decorator an EJB design pattern?

Answer :

No. Decorator design pattern, is the one which exhibits very low level runtime polymorphism, for the specific and single object (Instance of the class), but not for atleast for a class. It is the stuff to add specific functionality to a single & pointed object and leaves others like it unmodified. It is having close similarities like aspectJ stuff, but not with EJB stuff.


Question 14 :

What is the difference between sessioncontext and entitycontext?

Answer :

Since EnterpriseBeans live in a managed container, the container is free to call your EJB components methods at its leisure. The container houses the information like current status of bean,security credentials of the user currently accessing the bean in one object is called EJBContext Object. A context represents a way for beans to perform callbacks and modify their current status Sessioncontext is EJB context for session bean Entitycontext is EJB context for entity bean Message driven context is EJB context for message driven bean


Question 15 :

Does stateless Session bean create() method contain any parameters?

Answer :

Stateless SessionBean create() method doesnot contain any parameters and the syntax is as follows:
public interface XSessionEJBHome extends EJBHome {
XSessionEJB create() throws RemoteException, CreateException;
}