email article printer friendly get the code more resources

Plug 'n' Play Enterprise Apps
Enterprise application integration is made easy
with the J2EE Connector Architecture
by Tarak Modi

For companies that operate with multiple enterprise information systems (EISes), integrating these systems is critical to achieve the highest level of operational efficiency. Because J2EE support for enterprise application integration has been minimal (essentially, JMS and XML support it with the JAX APIs), Sun and its Java Community Process partners have proposed the J2EE Connector Architecture (JCA) standard as part of version 1.3 of the J2EE specification. The JCA provides a standard Java solution to the problem of connectivity between the many application servers and EISes already in existence.

Because the JCA provides a standard architecture for integrating heterogeneous EISes, EIS vendors that use it no longer need to customize their product for each application server. Application server vendors who conform to it do not need to add custom code when they want to add connectivity for a new EIS. Best of all, consumers who need to access EIS products from their J2EE applications do not need to learn and relearn different APIs, because the JCA defines a common client interface.

Inside JCA
The JCA defines a standard set of interfaces that allows connectors to integrate with compliant application servers seamlessly. At the same time, another standard set of interfaces allows clients (or applications hosted by the application server) to use the connectors in a uniform way. Thus with JCA, connectors are portable across application servers, and clients are portable across connectors.

JCA-compliant connectors are called resource adapters. Each resource adapter is required to support two sets of standard interfaces: a set of interfaces used by an application server to interact with the adapter, and another set used by the client/consumer to interact with the EIS (via the adapter, of course).

The JCA allows for compliant resource adapters to drop (most of) the client-side set in lieu of proprietary interfaces, but that may change in subsequent versions (remember the optional entity bean support in J2EE 1.0 and the optional Java Message Service (JMS) support in version 1.2?). I strongly advise that you always support the standard client side. It's not that much extra work, as I will demonstrate in the example resource adapter.

Before I delve into the example, though, let's first take a look at both the system- and client-side interfaces. Each JCA-compliant resource adapter must support a standard set of interfaces that is used by an application server to manage the adapter. This set of interfaces is the system-level contract between the adapter and the application server and is mandated by the JCA.