Jenkins: Outgoing SSL communication Docker Container

Just in case, do add your certificate to the OS itself.
What I usually do with my image is:

either create a new image, where I COPY mycert /usr/local/share/ca-certificates and RUN update-ca-certificates

or, for existing containers:

docker cp mycert my-container:/usr/local/share/ca-certificatesdocker exec -u root -t my-container update-ca-certificates

And double-check which jdk is actually used, in order to make sure you patched the right <jdk>/jre/lib/security/cacerts keystore.

CodeHunter