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Question 6 :

What does web module contain?

Answer :

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.

Question 7 :

What are the differences between Ear, Jar and War files? Under what circumstances should we use each one?

Answer :

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) are intended to hold generic libraries of Java classes, resources, auxiliary files, etc.
War files (files with a .war extension) are 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) are 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.

Question 8 :

What is the difference between Session bean and Entity bean ?

Answer :

The Session bean and Entity bean are two main parts of EJB container.

Session Bean
represents a workflow on behalf of a client
one-to-one logical mapping to a client.
created and destroyed by a client
not permanent objects
lives its EJB container(generally) does not survive system shut down
two types: stateless and stateful beans

Entity Bean
represents persistent data and behavior of this data
can be shared among multiple clients
persists across multiple invocations
findable permanent objects
outlives its EJB container, survives system shutdown
two types: container managed persistence(CMP) and bean managed persistence(BMP)

Question 9 :

What is "applet" ?

Answer :

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.

Question 10 :

What is "applet container" ?

Answer :

A container that includes support for the applet programming model.