WAS and Oracle Connection Not Available Cause being java.lang.AbstractMethodError

With a specific version of WAS ND, i.e., 7.0.0.15 and 7.0.0.17 the connection to a Oracle repository seems to always fail with Connection Not Available or something similar to this. If you are using an enterprise application you might see the "Attempt to start the Enterprise bean#bean id failed with an exception" and the cause might be a "java.lang.AbstractMethodError: java/sql/Wrapper.isWrapperFor(Ljava/lang/Class;)Z"

This is a known issue with the specific versions of WAS and APARs have been created to address the same. You can find the problem report and resolution summary in the below links
http://www-01.ibm.com/support/docview.wss?uid=swg1PM34365
http://www-01.ibm.com/support/docview.wss?uid=swg21474061

You can download the iFix from here.
http://www-01.ibm.com/support/docview.wss?uid=swg24029891

Why THIS has to be THIS only ??

This post is a placeholder of references to certain questions for which there is no definitive answer, but always good to know.

1. Why do we need abstract classes in Java? In other words whats the difference between an abstract class and a concrete class?

Check out here : http://stackoverflow.com/questions/10211317/how-is-abstract-class-different-from-concrete-class

2. Why NULL isn't nothing or empty string in Oracle?

A lot of time and lot of effort has been spent on this. Well that's how Oracle behaves. However there are ways in which this can be handled.

Check out here : http://www.oracle.com/technetwork/issue-archive/2005/05-jul/o45sql-097727.html