The problem was reported in

   https://stackoverflow.com/questions/48893994/groovy-in-org-mode-babel

I reproduced the problem locally. The basic error message is

  Caught: java.lang.ClassFormatError: Illegal class name "groovy-31624d60$isGolden"

The problem is the dash.

The patch replaces dashes with underscores when constructing temp file
names.

-- 
Nick