Answered: Should java.classpath combine classpath sources?

Sun, 15 Sep 2019 04:40:35 +0000

To expand on this slightly, the primary reason enumerating the classpath isn't straightforward is that Java has never defined a supported way to do it.

The system classloader, which generally loads the dependencies found on the java.class.path system property, is only guaranteed to be of type ClassLoader, which is not enumerable.

Until Java 9, it was possible to enumerate the system classloader by relying on an implementation detail: this reliably returned a URLClassLoader, which has a getURLs method. This was undocumented behavior, however.
Beginning with Java 9, the system classloader implementation was changed to an internal class that is not enumerable.
Using the java.class.path system property directly assumes certain runtime behavior, rather than inspecting the result of actual behavior. This assumption holds in many cases, but fails in others.

The ideal solution would be a way to enumerate resources loaded by the system (and possibly platform) classloader that works on Java 9+, so that the entire classpath hierarchy is enumerable.

Absent this, relying on the java.class.path property is likely necessary for Java 9+. If doing so, a next-best solution should accommodate at least two particular cases:

The application may be running in a container, and
Dynamic classloaders may add resources at runtime.

Answered: classpath "empty" when classpath 0.2.2 used with clojure maven plugin 1.3.20+

Wed, 26 Jun 2019 12:00:00 +0000

Reference: https://clojure.atlassian.net/browse/CLASSPATH-6 (reported by alex+import)

Clojure Q&A - Recent questions and answers in java.classpath

Answered: Should java.classpath combine classpath sources?

Answered: classpath "empty" when classpath 0.2.2 used with clojure maven plugin 1.3.20+