I have a similar issue, except when using Integer variables in the designer and the auto-generated task forms. In the link https://issues.jboss.org/browse/JBPM-3779 they mention a similar issue and say it was fixed for the JBPM 5.4 release, but I am currently using it an it is not working. I wonder if the two problems are related.
Hi Dhaval Shah,
have you managed to solve this issue?
Can you paste the code where you got this error?