J2EE.2.3 Product Extensions

This specification describes a minimum set of facilities that all J2EE products must provide. Most J2EE products will provide facilities beyond the minimum required by this specification. This specification includes only a few limits to the ability of a product to provide extensions. In particular, it includes the same restrictions as J2SE on extensions to Java APIs. A J2EE product may not add classes to the Java programming language packages included in this specification, and may not add methods or otherwise alter the signatures of the specified classes.

However, many other extensions are possible. A J2EE product may provide additional Java APIs, either other Java standard extensions or other (appropriately named) packages. A J2EE product may include support for additional protocols or services not specified here. A J2EE product may support applications written in other languages, or may support connectivity to other platforms or applications.

Of course, portable applications will not make use of any platform extensions. Applications that do make use of facilities not required by this specification will be less portable. Depending on the facility used, the loss of portability may be minor or it may be significant. The Java 2 Platform, Enterprise Edition Application Programming Model ^[1] will help application developers construct portable applications, and will contain advice on how best to manage the use of non-portable code when the use of such facilities is necessary.

^[1] Available at http://java.sun.com/j2ee/apm

In addition, we expect J2EE products to vary widely, and in fact compete , on various quality of service aspects. Different products will provide different levels of performance, scalability, robustness, availability, security, etc. In some cases this specification describes minimum required levels of service. Future versions of this specification may allow applications to describe their requirements in these areas.