I'm not entirely sure whether this belongs here or on StackOverflow, because it involves server admin, but it also involves a compiler.
It seems that the application on our Elastic Beanstalk cluster requires not just a JVM, but also a JDK, because it has the capability of installing extensions that it has to compile from Java source.
And we just now discovered, when we tried to use that capability on the cluster, instead of on a non-clustered development box, that the compiler isn't there.
Clearly, we need to customize what AWS uses to spin up new instances, so that it includes a working JDK.
But how?