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Special Section: J2EE FAQ's

What is J2EE and how does it relate to EJBs?
J2EE is a standard architecture to define and support an n-tier application programming model for building enterprise applications. It's based on standard design practices and patterns that simplify the application development by decoupling the components between the different tiers of an application. The three main tiers that are defined are the thin client, the business logic layer, and the data source layer. J2EE also encompasses security, performance, and integration issues with external (non-Java) environments.

Enterprise JavaBeans define the server-side component model used by J2EE to implement business logic and are the crux of the J2EE Platform. EJB design defines how to write distributed Java components that run in a J2EE-compliant application server. EJBs simplify development of middleware components by enabling them to be transactional, scalable, and portable. EJB components run only in the context of a J2EE application server, which acts as the "operating system" of the enterprise by handling such mundane tasks as EJB instantiation and destruction, transactions, persistence and recovery, and component deployment.

What are the J2EE Blueprints?
Last year Sun came out with a new set of design guidelines for building enterprise applications using enterprise Java APIs. These are collectively available as a set of documents called the J2EE Blueprints. These documents include architectural design guidelines for developing enterprise applications using the Java 2 Enterprise Edition APIs. The following quote from Sun's Web site describes the rationale behind the J2EE Blueprints:

The J2EE Blueprints provide an integrated set of documentation and examples that describe and illustrate "best practices" for developing and deploying component-based enterprise applications using the J2EE platform. The J2EE Blueprints are intended to help developers of e-commerce applications in the areas of component design and optimization, division of development labor, and allocation of technology resources.

The Blueprints are a great source of information and guidance for developers who are trying to get their arms around J2EE development. They run the gamut of APIs that comprise the J2EE platform. The Blueprints may be viewed in the same light as blueprints that are used to build a house. This set of guidelines outlines the tools at your disposal and the framework that can be used to build applications based on the J2EE APIs. More information about the Blueprints can be obtained from the following sources:
Overview: http://java.sun.com/j2ee/articles/blueprints.html
Download: http://java.sun.com/j2ee/download.html#blueprints
Book: Kassem, N., and the Enterprise Team. (2000). Designing Enterprise Applications with the Java Platform, Enterprise Edition, Addison-Wesley.

What is the Pet Store Demo and how can it help me understand J2EE application development?
The Pet Store Demo is an example application built based on the guidelines and design patterns that comprise the J2EE Blueprints. In other words, the Pet Store Application is akin to a model house built using the J2EE Blueprints.

The Pet Store is a complete end-to-end e-commerce application built using J2EE. However, it is a sample application. The demo acts as a great tutorial for understanding how to build Web-based e-commerce applications using J2EE. However, to build a real-world application, you will have to deal with issues including security, scalability, and performance, using the demo as a base. Some of the Java application server vendors have implemented the Pet Store Demo as a sample application built using their respective application server features.

More information on the Pet Store can be obtained from the following sources:
Architecture Overview: http://java.sun.com/j2ee/blueprints/jps11/archoverview.html
Book: Kassem, N., and the Enterprise Team. (2000). Designing Enterprise Applications with the Java Platform, Enterprise Edition, Addison-Wesley.
Application Servers: BEA Systems offers a tutorial using the Pet Store Demo as a base. The demo is documented in their standard documentation sets.

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