J2EE Overview

Java is one of the most commonly used and mature programming languages for building enterprise applications. Over the years, Java development has evolved from small applets run on a Web browser to large enterprise distributed applications run on multiple servers. Now, Java has three different platforms, or flavors, and each addresses certain programming requirements:

• The Java 2 Platform, Standard Edition (J2SE) is the underlying base platform for the J2EE. Therefore, a brief discussion on the J2SE platform is relevant to our discussion of the J2EE platform. The J2SE platform consists of the Java 2 Software Development Kit (SDK) and the Java 2 Runtime Environment (JRE). J2SE includes tools and application programming interfaces (APIs) for developing client applications with graphical user interfaces (GUIs), database access, directory access, Common Object Request Broker Architecture (CORBA), fine-grained security, input/output functions, and many other functions. It's the most widely used Java platform.

• The Java 2 Platform, Enterprise Edition (J2EE) is a platform for building server-side components and applications. It provides the infrastructure needed for these applications through a set of common services.

• The Java 2 Platform, Micro Edition (J2ME) helps with building Java applications for micro-devices with limited display and memory requirements (the entire API fits into 1KB), such as wireless devices, PDAs, and network devices.

Today, our focus is on the J2EE platform and its common services offerings.

J2EE is a platform and an industry-accepted standard that enables solutions for developing and deploying multitier enterprise applications. It provides a unified platform for building distributed, server-centric systems. J2EE is a set of standard APIs that is offered by a vendor through products and tools to be used by the enterprise. It was developed to meet recent enterprise requirements, such as diversity of both applications and data, in addition to the complexity of business processes. The J2EE standard is defined through a set of related specifications, such as the J2EE specification, the Enterprise JavaBeans specification, the Java Servlet specification, and the JavaServer Pages (JSP) specification.

The J2EE platform offers the following benefits to the enterprise and to product vendors:

• Establishes standards for database connectivity, Web components, business logic components, message-oriented middleware (MOM), communication protocols, and interoperability.

• Provides a standard for avoiding vendor lock-in and building portable applications and components that are flexible, expandable, and reliable. This also helps in developing secure, scalable, and transactional applications.

• Decreases time-to-market because much of the infrastructure and common services are provided by vendors' products that are implemented according to the standard J2EE specification. IT organizations can get out of the middleware business and concentrate on building applications for their business.

• Increases developer productivity because Java programmers can relatively easily learn J2EE technologies based on the Java language. All enterprise software development can be accomplished under the J2EE platform, using Java as the programming language.

• Promotes interoperability within existing heterogeneous systems, such as CORBA and J2EE.

• Enables developers to focus on supporting business process requirements rather than building the in-house application infrastructure. The application server handles the complex tasks of multithreading, synchronization, transactions, resource allocation, and life cycle management.

In general, the J2EE platform helps the enterprise to overcome certain issues such as programming productivity, application reliability, availability, security, scalability, and integration with existing systems.