I'd like to jump to Java jars that are on my classpath

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I'd like to have an ability to use Java source jars without relying solely on online documentation or other tools.
This may be a feature that should be developed together with Leiningen or as a Leiningen plugin. I'm not sure where to post it.

And if it's already possible to do then it's great. Then docs need an update.

Requests:

1. I want know what method/type signatures are used in imported Java objects. From a dependency, let's say it's from Leiningen. This feature shouldn't even need sources in the JAR.
2. I'd like to jump to Java source of a dependency (No, not to JDK) that has sources.
3. IntelliJ-like decompiler would be also very handy. IntelliJ decompiles any JAR if sources are not present and allows to inspect it's decompiled byte code. This is a great feature.
4. I'd like to retrieve Java docs if they exist in the jars.

I opened this issue because somebody steered the discussion of #2819 to talk about jumping to JDK's stdlib. Implying this this will close the issue.

This is awesome: https://practicalli.github.io/spacemacs/navigating-code/java-definitions.html (and probably should be done by default because java is on the $PATH anyway. Did they forget....?)
But it's not what I describe in this issue.
I'm talking about jumping to or inspecting imported JARs that are not part of Java's stdlib.

I use Spacemacs develop/5e037c889
Emacs 26.3
cider/cider-nrepl "0.25.0-SNAPSHOT"

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I found this: clojure-emacs/cider-nrepl#64
Closing. It'd be nice if that one would work...