1. What is J2EE?
J2EE is an environment for developing and deploying
enterprise applications. The J2EE platform consists of
a set of services, application programming interfaces
(APIs), and protocols that provide the functionality
for developing multitiered, web-based applications.
2. What is the J2EE module?
A J2EE module consists of one or more J2EE components
for the same container type and one component
deployment descriptor of that type.
3. What are the components of J2EE application?
A J2EE component is a self-contained functional
software unit that is assembled into a J2EE
application with its related classes and files and
communicates with other components. The J2EE
specification defines the following J2EE components:
Application clients and applets are client components.
Java Servlet and JavaServer PagesTM (JSPTM) technology
components are web components.
Enterprise JavaBeansTM (EJBTM) components (enterprise
beans) are business components.
Resource adapter components provided by EIS and tool
vendors.
4. What are the four types of J2EE modules?
1. Application client module
2. Web module
3. Enterprise JavaBeans module
4. Resource adapter module
5. What does application client module contain?
The application client module contains:
--class files,
--an application client deployment descriptoor.
Application client modules are packaged as JAR files
with a .jar extension.
6. What does web module contain?
The web module contains:
--JSP files,
--class files for servlets,
--GIF and HTML files, and
--a Web deployment descriptor.
Web modules are packaged as JAR files with a .war (Web
ARchive) extension.
7. What are the differences between Ear, Jar and War
files? Under what circumstances should we use each
one?
There are no structural differences between the files;
they are all archived using zip-jar compression.
However, they are intended for different purposes.
--Jar files (files with a .jar extension) arre
intended to hold generic libraries of Java classes,
resources, auxiliary files, etc.
--War files (files with a .war extension) arre
intended to contain complete Web applications. In this
context, a Web application is defined as a single
group of files, classes, resources, .jar files that
can be packaged and accessed as one servlet context.
--Ear files (files with a .ear extension) arre
intended to contain complete enterprise applications.
In this context, an enterprise application is defined
as a collection of .jar files, resources, classes, and
multiple Web applications.
Each type of file (.jar, .war, .ear) is processed
uniquely by application servers, servlet containers,
EJB containers, etc.
8. What is the difference between Session bean and
Entity bean?one?
The Session bean and Entity bean are two main parts of
EJB container.
Session Bean
--represents a workflow on behalf of a cliennt
--one-to-one logical mapping to a client. --created
and destroyed by a client
--not permanent objects
--lives its EJB container(generally) does noot survive
system shut down
--two types: stateless and stateful beans Entity Bean
--represents persistent data and behavior off this
data
--can be shared among multiple clients
--persists across multiple invocations
--findable permanent objects
--outlives its EJB container, survives systeem
shutdown
--two types: container managed persistence(CCMP) and
bean managed persistence(BMP)
9. What is "applet"
A J2EE component that typically executes in a Web
browser but can execute in a variety of other
applications or devices that support the applet
programming model.
10. What is "applet container"
A container that includes support for the applet
programming model.
