Enterprise J2ME Developing Mobile Java Applications [Electronic resources] نسخه متنی

2.3 Java Everywhere

The conference theme of the 8th JavaOne conference in 2003 is "Java Everywhere." Beyond the buzz and the hype, the Java Everywhere vision signals a departure from Java's traditional focus on "Write Once Run Anywhere" (WORA). Instead, it promotes a single consistent architecture, compatible APIs and easy skill migration for developers. Java Everywhere will have profound impacts on Java-based mobility solutions.

2.3.1 The Single Architecture Solution

Although cross-platform compatibility is a key concept behind the Java philosophy, Java designers also realize that portability has its limits. Portability is only meaningful among similar OSs and hardware platforms. Today, the Java platform is partitioned into three editions, all of which have significant roles in mobility. The overall architecture of the Java platform is shown in Figure 2.1.

The Java 2 Standard Edition (J2SE): The J2SE is the basis of the Java platform. It defines the JVMs and libraries that run on standard PCs and workstations. In the mobility world, J2SE is the ideal choice for wireless laptop-based applications.

The Java 2 Enterprise Edition (J2EE): The J2EE is J2SE plus a large number of serverside APIs, containers and tools. It aims to implement complex application servers. J2EE application servers can drive browser-based (e.g., WML and xHTML) mobile applications and become service end-points for smart mobile clients.

The Java 2 Micro Edition (J2ME): J2ME is a Java platform that is designed for small devices. It contains specially designed, lightweight virtual machines; a bare minimum of core-class libraries; and lightweight substitutes for standard Java libraries. J2ME is the ideal mobile client platform for wireless PDAs and enhanced mobile phones.

Applications for each of the Java editions can follow similar architectures. That allows companies to leverage existing developer talent, cut cost and build more maintainable products.

2.3.2 Opportunities for J2EE Developers

The single architecture approach benefits existing Java developers the most. As the serverside technologies reach maturity, consolidation and outsourcing become the trend. According to a U.S. Department of Commerce study, in year 2002, the IT employment in the United States fell for the first time in history. Many J2EE development projects have been moved to cheaper offshore locations.

Enterprise developers have to keep up with the need of their customers and stay on top of the innovation value chain to stay employed. As more companies look for IT solutions to improve mobile workers' productivity, enterprise mobility is a natural next step for developers. Fortunately, with the Java Everywhere architecture, it is easy for experienced J2EE developers to migrate their skills to the mobile arena. For example,

Common J2EE design patterns can be applied to end-to-end applications with little change.

Mobile enterprise messaging, data access, integration and security solutions are parallel to their serverside counterparts.

Lightweight editions of popular J2EE frameworks are already available on J2ME.

In the rest of this book, we will discuss the above topics in detail.