J2EE Interview Questions and Answers - DoAnswers.com

The Java 2 Enterprise Edition is a collection of related specifications and corresponding documentation that describe an enterprise-level computing architecture for the Java platform. J2EE containers, also known as application servers, such as JBoss, WebLogic, WebSphere, and others typically implement the penultimate (next-to-latest) version of the specification. ...Java 2 Platform, Enterprise Edition or J2EE is a programming platform for developing and running distributed multi-tier architecture applications, based largely on modular components running on an application server. The J2EE platform is defined by a specification. J2EE is also considered informally to be a language or standard because providers must agree to certain conformance requirements in order to declare their products as J2EE compliant; albeit with no ISO or ECMA standard.

J2EE Interviews are getting tough these days as the technology grows faster. To get through the J2EE interview one needs to update him/herself in a regular manner. Having said that, just before the interview, it is very important to have a quick glance of the reputed J2EE questions and answers to make yourself comfortable during the interview process. This is where DoAnswers.com helps you in renewing yourself on J2EE and various other technologies interview preparation.

Enterprise Java Beans (EJB) Interview Questions And Answers

The EJB specification is one of several Java APIs in the Java Platform, Enterprise Edition. EJB is a server-side model that encapsulates the business logic of an application. The EJB specification was originally developed in 1997 by IBM and later adopted by Sun Microsystems (EJB 1.0 and 1.1) and enhanced under the Java Community Process as JSR 19 (EJB 2.0), JSR 153 (EJB 2.1) and JSR 220 (EJB 3.0).

The EJB specification intends to provide a standard way to implement the back-end 'business' code typically found in enterprise applications (as opposed to 'front-end' user-interface code). Such code was frequently found to reproduce the same types of problems, and it was found that solutions to these problems are often repeatedly re-implemented by programmers. Enterprise JavaBeans were intended to handle such common concerns as persistence, transactional integrity, and security in a standard way, leaving programmers free to concentrate on the particular problem at hand.

Hibernate Interview Questions And Answers

Hibernate's primary feature is mapping from Java classes to database tables (and from Java data types to SQL data types). Hibernate also provides data query and retrieval facilities. Hibernate generates the SQL calls and relieves the developer from manual result set handling and object conversion, keeping the application portable to all SQL databases, with database portability delivered at very little performance overhead.

Hibernate provides transparent persistence for Plain Old Java Objects (POJOs). The only strict requirement for a persistent class is a no-argument constructor, not compulsorily public. (Proper behavior in some applications also requires special attention to the equals() and hashCode() methods.)

Hibernate provides a dirty checking feature that avoids unnecessary database write actions by performing SQL updates only on the modified fields of persistent objects.

Hibernate can be used both in standalone Java applications and in Java EE applications using servlets or EJB session beans.

Jave Messaging Service (JMS) Interview Questions And Answers

The Java Message Service (JMS) defines the standard for reliable Enterprise Messaging. Enterprise messaging, often also referred to as Messaging Oriented Middleware (MOM), is universally recognized as an essential tool for building enterprise applications. By combining Java technology with enterprise messaging, the JMS API provides a powerful tool for solving enterprise computing problems.

Enterprise messaging provides a reliable, flexible service for the asynchronous exchange of critical business data and events throughout an enterprise. The JMS API adds to this a common API and provider framework that enables the development of portable, message based applications in the Java programming language.

The JMS API improves programmer productivity by defining a common set of messaging concepts and programming strategies that will be supported by all JMS technology-compliant messaging systems.

The JMS API is an integral part of the Java 2, Enterprise Edition (J2EE) platform, and application developers can use messaging with components using J2EE APIs ("J2EE components").

Version 1.1 of the JMS API in the J2EE 1.4 platform has the following features:

1. Message-driven beans enable the asynchronous consumption of JMS messages.

2. Message sends and receives can participate in Java Transaction API (JTA) transactions.

3. J2EE Connector Architecture interfaces that allow JMS implementations from different vendors to be externally plugged into a J2EE 1.4 application server.

The addition of the JMS API enhances the J2EE platform by simplifying enterprise development, allowing loosely coupled, reliable, asynchronous interactions among J2EE components and legacy systems capable of messaging. As a developer, you can easily add new behavior to a J2EE application with existing business events by adding a new message-driven bean to operate on specific business events.

The J2EE platform's Enterprise JavaBeans (EJB) container architecture, moreover, enhances the JMS API in two ways:

1. By allowing for the concurrent consumption of messages

2. By providing support for distributed transactions, so that database updates, message processing, and connections to EIS systems using the J2EE Connector Architecture can all participate in the same transaction context.

Jave Server Faces (JSF) Interview Questions And Answers

JavaServer Faces technology includes:

1. A set of APIs for representing UI components and managing their state, handling events and input validation, defining page navigation, and supporting internationalization and accessibility.

2. A JavaServer Pages (JSP) custom tag library for expressing a JavaServer Faces interface within a JSP page.

Designed to be flexible, JavaServer Faces technology leverages existing, standard UI and web-tier concepts without limiting developers to a particular mark-up language, protocol, or client device. The UI component classes included with JavaServer Faces technology encapsulate the component functionality, not the client-specific presentation, thus enabling JavaServer Faces UI components to be rendered to various client devices. By combining the UI component functionality with custom renderers, which define rendering attributes for a specific UI component, developers can construct custom tags to a particular client device. As a convenience, JavaServer Faces technology provides a custom renderer and a JSP custom tag library for rendering to an HTML client, allowing developers of Java Platform, Enterprise Edition (Java EE) applications to use JavaServer Faces technology in their applications.

Ease-of-use being the primary goal, the JavaServer Faces architecture clearly defines a separation between application logic and presentation while making it easy to connect the presentation layer to the application code. This design enables each member of a web application development team to focus on his or her piece of the development process, and it also provides a simple programming model to link the pieces together. For example, web page developers with no programming expertise can use JavaServer Faces UI component tags to link to application code from within a web page without writing any scripts.

Developed through the Java Community Process under JSR-127, JavaServer Faces technology establishes the standard for building server-side user interfaces. With the contributions of the expert group, the JavaServer Faces APIs are being designed so that they can be leveraged by tools that will make web application development even easier. Several respected tools vendors were members of the JSR-127 expert group, which developed the JavaServer Faces 1.0 specification. These vendors are committed to supporting the JavaServer Faces technology in their tools, thus promoting the adoption of the JavaServer Faces technology standard.

The expert group is actively developing the specification for JavaServer Faces version 1.2. To check its current status, please see JSR-252.

Java Server Pages (JSP) Interview Questions And Answers

JavaServer Pages (JSP) technology enables Web developers and designers to rapidly develop and easily maintain, information-rich, dynamic Web pages that leverage existing business systems. As part of the Java technology family, JSP technology enables rapid development of Web-based applications that are platform independent. JSP technology separates the user interface from content generation, enabling designers to change the overall page layout without altering the underlying dynamic content.

Benefits for Developers

If you are a Web page developer or designer who is familiar with HTML, you can:

Use JSP technology without having to learn the Java language: You can use JSP technology without learning how to write Java scriplets. Although scriptlets are no longer required to generate dynamic content, they are still supported to provide backward compatibility.

Extend the JSP language: Java tag library developers and designers can extend the JSP language with "simple tag handlers," which utilize a new, much simpler and cleaner, tag extension API. This spurs the growing number of pluggable, reusable tag libraries available, which in turn reduces the amount of code needed to write powerful Web applications.

Easily write and maintain pages: The JavaServer Pages Standard Tag Library (JSTL) expression language is now integrated into JSP technology and has been upgraded to support functions. The expression language can now be used instead of scriptlet expressions.

Servlets Interview Questions And Answers

Servlets are the Java platform technology of choice for extending and enhancing Web servers. Servlets provide a component-based, platform-independent method for building Web-based applications, without the performance limitations of CGI programs. And unlike proprietary server extension mechanisms (such as the Netscape Server API or Apache modules), servlets are server- and platform-independent. This leaves you free to select a "best of breed" strategy for your servers, platforms, and tools.

Servlets have access to the entire family of Java APIs, including the JDBC API to access enterprise databases. Servlets can also access a library of HTTP-specific calls and receive all the benefits of the mature Java language, including portability, performance, reusability, and crash protection.

Today servlets are a popular choice for building interactive Web applications. Third-party servlet containers are available for Apache Web Server, Microsoft IIS, and others. Servlet containers are usually a component of Web and application servers, such as BEA WebLogic Application Server, IBM WebSphere, Sun Java System Web Server, Sun Java System Application Server, and others.

You might want to check out the latest information on JavaServer Pages (JSP) technology. JSP technology is an extension of the servlet technology created to support authoring of HTML and XML pages. It makes it easier to combine fixed or static template data with dynamic content. Even if you're comfortable writing servlets, there are several compelling reasons to investigate JSP technology as a complement to your existing work.

Spring Framework Interview Questions And Answers

Spring is a layered Java/J2EE application framework, based on code published in Expert One-on-One J2EE Design and Development by Rod Johnson (Wrox, 2002).

Spring includes:

1. The most complete lightweight container, providing centralized, automated configuration and wiring of your application objects. The container is non-invasive, capable of assembling a complex system from a set of loosely-coupled components (POJOs) in a consistent and transparent fashion. The container brings agility and leverage, and improves application testability and scalability by allowing software components to be first developed and tested in isolation, then scaled up for deployment in any environment (J2SE or J2EE).

2. A common abstraction layer for transaction management, allowing for pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Generic strategies for JTA and a single JDBC DataSource are included. In contrast to plain JTA or EJB CMT, Spring's transaction support is not tied to J2EE environments.

3. A JDBC abstraction layer that offers a meaningful exception hierarchy (no more pulling vendor codes out of SQLException), simplifies error handling, and greatly reduces the amount of code you'll need to write. You'll never need to write another finally block to use JDBC again. The JDBC-oriented exceptions comply to Spring's generic DAO exception hierarchy.

4. Integration with Toplink, Hibernate, JDO, and iBATIS SQL Maps: in terms of resource holders, DAO implementation support, and transaction strategies. First-class Hibernate support with lots of IoC convenience features, addressing many typical Hibernate integration issues. All of these comply to Spring's generic transaction and DAO exception hierarchies.

5. AOP functionality, fully integrated into Spring configuration management. You can AOP-enable any object managed by Spring, adding aspects such as declarative transaction management. With Spring, you can have declarative transaction management without EJB... even without JTA, if you're using a single database in Tomcat or another web container without JTA support.

6. A flexible MVC web application framework, built on core Spring functionality. This framework is highly configurable via strategy interfaces, and accommodates multiple view technologies like JSP, Velocity, Tiles, iText, and POI. Note that a Spring middle tier can easily be combined with a web tier based on any other web MVC framework, like Struts, WebWork, or Tapestry.

You can use all of Spring's functionality in any J2EE server, and most of it also in non-managed environments. A central focus of Spring is to allow for reusable business and data access objects that are not tied to specific J2EE services. Such objects can be reused across J2EE environments (web or EJB), standalone applications, test environments, etc without any hassle.

Spring's layered architecture gives you a lot of flexibility. All its functionality builds on lower levels. So you can e.g. use the JavaBeans configuration management without using the MVC framework or AOP support. But if you use the web MVC framework or AOP support, you'll find they build on the configuration framework, so you can apply your knowledge about it immediately.

Struts Framework Interview Questions And Answers

Jakarta Apache Struts 2 is an elegant, extensible framework for creating enterprise-ready Java web applications. The framework is designed to streamline the full development cycle, from building, to deploying, to maintaining applications over time.

Apache Struts 2 was originally known as WebWork 2. After working independently for several years, the WebWork and Struts communities joined forces to create Struts2. This new version of Struts is simpler to use and closer to how Struts was always meant to be.