As per the documentation for the jndi ldap provider (http://www.faqs.org/rfcs/rfc2713.html), providing multiple values for the javaCodebase attribute should all the jndi client to load from each of the codebases

"3.2 javaCodebase

   ...

   If the javaCodebase attribute contains more than one value, each
   value is an independent codebase. That is, there is no relationship
   between the URLs in one value and those in another; each value can be
   viewed as an alternate source for loading the Java class definition.
   See [Java] for information regarding class loading."

However, when I specify two javaCodebase attribute values, each refering to different urls to the same jar file, only the first value appears to be used. That is, if the http server the first url references is down, classes are not loaded from the url specified in the second value. Rather, I just get errors that indicate the classes cannot be found.