JCA

As you can read for yourself toward the end of this chapter, JCA (J2EE Connector Architecture) is a standard adapter architecture that provides adapter interoperability between integration servers by offering standard mechanisms for communicating with source or target systems. The purpose of our JCA discussion here is not to provide all of the details about JCA; there are plenty of other places to find more detailed information, including the current spec that can be found at www.java.sun.com. My goal is to provide some basic information and, more importantly, put JCA into perspective, with our discussion in the first part of this chapter taken into consideration. It's also important to understand that JCA is not a new set of adapter services. What JCA brings to the table is a standard mechanism to create and deploy adapters...something we've yet to provide as an industry.

To understand the need for JCA, we must first understand that, although most application integration technology vendors offer adapters, the adapters they offer are very different and don't work and play well with others. For example, you can't take adapters from WebMethods and make them work with Vitria adapters without a lot of redevelopment on the vendor's side. They are not interchangeable.

It's also important to mention that JCA is Java centric (the J in JCA stands for J2EE), designed to be invoked from a J2EE container. Considering this, it could be an architectural mismatch for those shops that are non-Java. However, it's clearly okay to leverage JCA adapters from non-Java environments. Due to market momentum, most application integration technologies Java centric or not will leverage JCA.

Is JCA Thick or Thin?

JCA is a standard adapter architecture that provides adapter interoperability between integration servers by offering standard mechanisms for communicating with source or target systems. So, if JCA is a type of adapter, is it thick or is it thin?

Considering the capabilities of JCA both existing and proposed JCA adapters are more thin than thick. They provide a simple abstraction layer on top of the existing source or target application interface. JCA provides some metadata capabilities, based on XML, as well as resource management, but JCA lacks the intelligence to handle exceptions or think on its own when communication with the integration server is absent.

JCA-based adapters may provide these capabilities in the future, but for now, JCA adapters are lean and mean.

Finally, one of the opportunities and challenges of JCA is the notion that packaged application vendors and other third parties will build and support JCA adapters the idea being that many packaged application and middleware vendors will develop JCA adapters that are usable with a variety of application and integration servers. They are interchangeable, because all JCA developers comply with a single specification and a single set of services and interfaces.