Replaceable Components and the Service Provider Interface

Several popular component-based standards have emerged recently, including JavaBeans and Enterprise JavaBeans from Sun Microsystems and the Component Object Model from Microsoft. These component models are being adopted for use in software development, as they eliminate opportunities for architectural mismatch and are supported by standard services. A highly touted property of component models is that they support the development of replaceable components. Unfortunately, a robust, commercial marketplace of replaceable components has not been established for any of these component models. On the other hand, the properties of the Service Provider Interface (SPI), used in many Java language packages, has resulted in the development of reusable components in several technology areas. Examples of successful SPI packages include Java Database Connectivity, Java Cryptography Extension, Java Naming and Directory Interface, and the Java Application Program Interface for XML Processing. This technical note considers the motivation for using replaceable components and defines the requirements of replaceable component models. It evaluates the properties of standard component models and the SPI approach that affect their ability to support replaceable components.