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EJB Interview Questions and Answers
What are the two important
TCP Socket classes?
Socket and ServerSocket.
ServerSocket is used for normal two-way socket communication. Socket class
allows us to read and write through the sockets. getInputStream() and
getOutputStream() are the two methods available in Socket class.
What technologies are
included in J2EE?
The main technologies in J2EE are: Enterprise JavaBeansTM (EJBsTM),
JavaServer PagesTM (JSPsTM), Java Servlets, the Java Naming and Directory
InterfaceTM (JNDITM), the Java Transaction API (JTA), CORBA, and the JDBCTM
data access API.
What is the difference
between EJB and Java beans?
EJB is a specification for J2EE server, not a product; Java beans may be a
graphical component in IDE.
What is EJB role in
J2EE?
EJB technology is the core of J2EE. It enables developers to write reusable
and portable server-side business logic for the J2EE platform.
Tell me something about
Local Interfaces.
EJB was originally designed around remote invocation using the Java Remote
Method Invocation (RMI) mechanism, and later extended to support to standard
CORBA transport for these calls using RMI/IIOP. This design allowed for
maximum flexibility in developing applications without consideration for the
deployment scenario, and was a strong feature in support of a goal of
component reuse in J2EE. Many developers are using EJBs locally, that is,
some or all of their EJB calls are between beans in a single container. With
this feedback in mind, the EJB 2.0 expert group has created a local
interface mechanism. The local interface may be defined for a bean during
development, to allow streamlined calls to the bean if a caller is in the
same container. This does not involve the overhead involved with RMI like
marshalling etc. This facility will thus improve the performance of
applications in which co-location is planned. Local interfaces also provide
the foundation for container-managed relationships among entity beans with
container-managed persistence.
What is Enterprise
JavaBeans (EJB) container?
It manages the execution of enterprise beans for J2EE applications.
Enterprise beans and their container run on the J2EE server.
What is in-memory
replication?
The process by which the contents in the memory of one physical m/c are
replicated in all the m/c in the cluster is called in-memory replication.
What is Ripple Effect?
The process of propagating the changes in the properties of a server group
during runtime to all the associated clones is called Ripple Effect.
What is a Clone?
The copies of a server group are called Clones. But unlike a Server Group
Clones are associated with a node and are real server process running in
that node.
What are the types of
Scaling
There are two types of scaling: Vertical Scaling and Horizontal Scaling.
Vertical Scaling - When multiple server clones of an application server are
defined on the same physical m/c, it is called Vertical Scaling. The
objective is to use the processing power of that m/c more efficiently.
Horizontal Scaling - When Clones of an application server are defined on
multiple physical m/c, it is called Horizontal Scaling. The objective is to
use more than one less powerful m/c more efficiently.
What is a Server Group?
A server group is a template of an Application Server(and its contents) i.e,
it is a logical representation of the application server. It has the same
structure and attributes as the real Application Server, but it is not
associated with any node, and does not correspond to any real server process
running on any node.
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