This is not a definitive answer, but I got very frustrated trying to get Java to accept non-standard certificates. Since this is a development server, perhaps you could turn off the "Require SSL connections" in the site settings, and connect via "http:".

There is also some pointers to discussion on this topic here

https://www.labkey.org/announcements/home/Developer/Forum/thread.view?entityId=9021b8ac-857c-102c-86c6-d104f9cdea0a

Matt