Can you please tell me whether there is any co-relation between JCA (Java Connector Architecture) and JMX (Java Management eXtension) infrastructure? What is the difference between them? How do both of them help in building plug-in applications or adapters?
From an API point of view, there isn't much correlation between the two. JCA and JMX are two separate standardization efforts, that will eventually lead to two different API packages. (Even though both standards use the term "connector" and "adapter" a lot, but in very different contexts).
JCA is about "connectors" for J2EE application servers, that let your J2EE applications tap into ERP systems, JMS servers, etc. in a standardized manner.
JMX is about network management, in the sense of SNMP, CMIP, Tivoli, etc. JMX specifies instrumentation design patterns (MBeans), an MBean server and a client interface that should allow any JMX administration client to work with any MBean server, and any MBean server to be used to administer any application whose objects have been instrumented as MBeans.
You will find more information about JMX on http://java.sun.com/products/JavaManagement/
You will find more information about JCA on http://java.sun.com/j2ee/connector/