Can't turn on plantuml-mode in Emacs

Question

I am on Emacs 24.3.1. I installed the MELPA version of plantuml-mode via

M-x package-install RET plantuml-mode RET.

When I try to turn on plantuml-mode for a buffer, I get the following error:

Wrong type argument: stringp, nil

Trying to find additional installation instructions I looked at the "Commentary" section in the plantuml-mode.el source, but there it only says to require the package, and I am doing that.

How can I fix this problem?

Answer 1

After a bit more digging I found the solution to this problem: plantuml-mode won't run unless the variable plantuml-jar-path is set to a non-nil value. Fairly obvious in hindsight, but still easy to get bit by since it isn't mentioned explicitly (at least not anywhere that I could find). For best results, the variable should point to the location of the plantuml.jar file in your file system. In my case:

(setq plantuml-jar-path "/opt/plantuml/plantuml.jar")

Hope this helps someone else at some point.