25.1. Introducing the Connector Architecture

The Java Connector Architecture (Connectors) defines a way for enterprise applications (based on EJB, Servlet, JSP, or J2EE clients) to communicate with existing external Enterprise Information Systems (EIS) through an application server such as JOnAS. This requires the use of a third-party software component called a Resource Adapter (RA) for each type of EIS. A Resource Adapter is an architecture component, comparable to a software driver, that connects the EIS, the application server, and the enterprise application. The RA is generally made available by an EIS vendor.

The RA provides an interface (the Common Client Interface or CCI) to the enterprise application (EJBs) for accessing the EIS. The RA also provides standard interfaces for plugging into the application server, so that the EIS and application server can collaborate to keep all system-level mechanisms transparent from the application components. The application performs "business logic" operations on the EIS data using the RA client API (CCI), while transactions, connections (including pooling), and security on the EIS is managed by JOnAS through the RA (system contract).