Question: What is J2EE? Answer: J2EE Stands for Java 2 Enterprise Edition. J2EE is an environment for developing and deploying enterprise applications.
Question: What is J2EE? Answer: J2EE Stands for Java 2 Enterprise Edition. J2EE is an environment for developing and deploying enterprise applications.Question: What
do you understand by a J2EE module?
Answer: A J2EE module is a software unit that consists of one or more J2EE components of the same container type
along with one deployment descriptor of that type. J2EE specification
defines four types of modules:
a) EJB
b) Web
c) application client and
d) resource adapter
In the J2EE applications modules can be deployed as stand-alone units. Modules
can also be assembled into J2EE applications.
Question: Tell
me something about J2EE component?
Answer: J2EE component is a
self-contained functional software unit supported by a container
and configurable at deployment time. The J2EE specification defines the
following J2EE components:
Question:
Differentiate between .ear, .jar and .war files.
Answer: These files are simply zipped file using java jar tool. These
files are created for different purposes. Here is the description of these
files:
.jar files: These files are with the .jar extenstion. The .jar files
contains the libraries, resources and accessories files like property files.
.war files: These files are with the .war extension. The war file
contains the web application that can be deployed on the any servlet/jsp
container. The .war file contains jsp, html, javascript and other files for
necessary for the development of web applications.
.ear files: The .ear file contains the EJB modules of the
application.
Question:
What is the difference between Session Bean and Entity Bean?
Answer:
Session Bean: Session is one of the EJBs and it represents a single client inside the Application Server. Stateless session is easy to develop and its efficient. As compare to entity beans session beans require few server resources.
A session bean is similar to an interactive session and is not shared; it can have only one client, in the same way that an interactive session can have only one user. A session bean is not persistent and it is destroyed once the session terminates.
Entity Bean: An entity bean represents persistent global data from the
database. Entity beans data are stored into database.
Question: Why
J2EE is suitable for the development distributed multi-tiered enterprise
applications?
Answer: The J2EE platform consists of multi-tiered distributed application model.
J2EE applications allows the developers to design and implement the business
logic into components according to business requirement. J2EE architecture
allows the development of multi-tired applications and the developed
applications can be installed on different machines depending on the tier in the
multi-tiered J2EE environment . The J2EE application parts are:
a) Client-tier components run on the client machine.
b) Web-tier components run on the J2EE server.
c) Business-tier components run on the J2EE server and the
d) Enterprise information system (EIS)-tier software runs on the EIS servers
Question: Why do
understand by a container?
Answer: Normally, thin-client multi-tiered applications are hard to write because they involve many lines of intricate code to handle transaction and state management, multithreading, resource pooling, and other complex low-level details. The component-based and platform-independent J2EE architecture makes J2EE applications easy to write because business logic is organized into reusable components. In addition, the J2EE server provides
underlying services in the form of a container for every component type. Because you do not have to develop these services yourself, you are free to concentrate on solving the business problem at
hand (Source: http://java.sun.com/j2ee/1.3/docs/tutorial/doc/Overview4.html
).
In short containers are the interface between a component and the low-level platform specific functionality that supports the component.
The application like Web, enterprise bean, or application client component
must be assembled and deployed on the J2EE container before executing.
Question: What
are the services provided by a container?
Answer: The services provided by container are as follows:
a) Transaction management for the bean
b) Security for the bean
c) Persistence of the bean
d) Remote access to the bean
e) Lifecycle management of the bean
f) Database-connection pooling
g) Instance pooling for the bean
Question: What
are types of J2EE clients?
Answer: J2EE clients are the software that access the services
components installed on the J2EE container. Following are the J2EE clients:
a) Applets
b) Java-Web Start clients
c) Wireless clients
d) Web applications
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