J2EE Interview Questions and Answers

What is J2EE?

J2EE is a Java 2 Enterprise Edition. J2EE is an environment for developing and deploying enterprise applications. J2EE specification is defined by Sun Microsystems Inc. The J2EE platform is lies of a set of services, application programming interfaces (APIs), and protocols, which provides the functionality necessary for developing multi-tiered, web-based applications. The J2EE platform is one of the richest platform for the development and deployment of enterprise applications.

What do you understand by a J2EE module?

A J2EE module is a software building block that consists of one or more than J2EE components of the same container type along with one deployment descriptor of that type. J2EE specification specifies four characters of modules:
a) Web module
b) EJB module
c) resource adapter
d) application client and

Modules can also be assembled into J2EE applications.

What is J2EE component?

J2EE component is a collected functional software unit supported by a container and configurable at deployment time. The J2EE specification shows the following J2EE component part:

* Application clients and applets that run on the client machine.

* Java servlet and JavaServer Pages (JSP) technology are Web components that run on the server machine.

* Enterprise JavaBeans (EJB) (enterprise beans) are business components that run on the server.

What is bean-managed transaction ?
Transaction whose boundaries are defined by an enterprise bean.


What is binding (XML) ?
Generating the code needed to process a well-defined portion of XML data.


What is binding (JSF) ?
Wiring UI components to back-end data sources such as backing bean properties.


What is build file ?
The XML file that contains one or more asant targets.



What is business logic ?
The code that implements the functionality of an application.



What is business method ?
A method of an enterprise bean that implements the business logic or rules of an application.


What is callback methods ?
Component methods called by the container to notify the component of important events in its life cycle.


What is caller principal ?
It is principal that identifies the invoker of the enterprise bean method.



What is caller ?
Same as caller principal.



What are the components of web module?

There are the following modules:
a) Java classes
b) JSP files
c) gif and html files and
d) web component deployment descriptors



Differentiate .ear, .jar and .war files?

These files are created for different uses .These files are only zipped file using java jar tool. Here is the description of these files:

.ear files: The .ear file comprises the EJB modules of the application.
.jar files: are with the .jar extension. The .jar files comprises the libraries, resources and accessories files like property files.
.war files: are with the .war extension. The war file comprises 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.


Differentiate between Session Bean and Entity Bean?

Session Bean: Session is one of the EJB and it shows a single client inside the Application Server. Stateless session bean is easy to develop and its efficient. As compare to entity beans session beans needs few server resources.

Entity Bean: An entity bean represents persistent global data from the database. Entity beans data are stored into database.



Why J2EE is suitable for the development of distributed multi-tiered enterprise applications?

J2EE application program 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) Web-tier components.
b) Client-tier components .
c) Business-tier components .
d) Enterprise information system (EIS)-tier software.



what is a container?

containers are the interface between a component and the low-level platform specific functionality that supports the component.



What services provided by a container?

The services provided by container are as follows:
a) Transaction management for the bean
b) Instance pooling for the bean
c) Persistence
d) Remote access
e) Lifecycle management
f) Database-connection pooling
g) Security



What are types of J2EE clients?

a) Java-Web Start
b) clients Applets
c) Web applications
d) Wireless clients



What is Deployment Descriptor?

A deployment descriptor is simply an XML(Extensible Markup Language) file with the extension of .xml.. Application servers reads the deployment descriptor to deploy the components contained in the deployment unit. As in: ejb-jar.xml file is used to describe the setting of the EJB.



What is JTA and JTS?

JTA stands for Java Transaction API and JTS stands for Java Transaction Service. JTA provides a standard interface which allows the developers to demarcate transactions . JTA is a high level transaction interface used by the application code to control the transaction.


What is JAXP?

The Java API for XML Processing (JAXP) enables applications to parse and transform XML documents independent of a particular XML processing implementation.

What is J2EE Connector architecture?

J2EE Connector Architecture (JCA) is a Java-based technology solution for connecting application servers and enterprise information systems (EIS) as part of enterprise application integration (EAI) solutions.

differentiate between Java Bean and Enterprise Java Bean?

Java Bean as is a plain java class with member variables and getter setter methods. Java Beans are defined under JavaBeans specification as Java-Based software component model. which lets in the features like introspection, customization, events, properties and persistence.

Differentiate JTS and JTA?

JTS shows the implementation of a Java transaction manager. JTS specifies the implementation of a Transaction Manager which supports the Java Transaction API (JTA) 1.0.
The JTA shows an architecture for building transactional application servers and defines a set of interfaces for various components of this architecture. The components are: the application, resource managers, and the application server.



Can Entity Beans have no create() methods?

Entity Beans have no create() method, when entity bean is not used to store the data in the database. In this case entity bean is used to retrieve the data from database.



What are the call back methods in Session bean?

Callback methods are called by the container to notify the important events to the beans in its life cycle. The callback methods example are ejbCreate(), ejbPassivate(), and ejbActivate().



What is bean managed transaction?

In the EJB transactions can be maintained by the container or developer can write own code to maintain the transaction. If a developer doesn’t want a Container to manage transactions, developer can write own code to maintain the database transaction.



What are transaction isolation levels in EJB?

There are four levels :
* Serializable
* Committed Read
* Repeatable Read
* Uncommitted Read



What is "application client" ?
Application clients have access to some J2EE platform APIs.


What is "application client container" ?
A container that supports application client components.


What is "application client module" ?
A software unit that have one or more classes and an application client deployment descriptor.


What is "application component provider" ?
A vendor that provides the Java classes that implement components' methods, JSP page definitions, and any required deployment descriptors.


What are "application configuration resource file" ?
An XML file used to configure resources for a Java Server Faces application.

What is "archiving" ?

Process of saving the state of an object and restoring it.


What is "asant" ?
A Java-based build tool that can be extended using Java classes. The configuration files are XML-based, calling out a target tree where various tasks get executed.


What is "attribute"?
A qualifier on an XML tag that provides additional information to the client .


What is authentication ?
Process that verifies the identity of a user, device, or other entity in a computer system.

What is authorization ?
The process by which access to a method or resource is determined.

What is authorization constraint ?
An rule that determines who is permitted to access a Web resource collection.


What is B2B ?
B2B stands for Business-to-business process.


What is backing bean ?

The backing bean defines properties for the components on the page and methods that perform processing for the component.


What is basic authentication ?
An authentication mechanism in which a Web server authenticates an entity via a user name and password obtained using the Web application's built-in authentication mechanism.


What is bean-managed persistence ?
The mechanism whereby data transfer between an entity bean's variables and a resource manager is managed by the entity bean.


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