This process requires keytool and openssl.
keytool -importkeystore -srckeystore my_in_file.jks -destkeystore my_out_file.p12 -deststoretype PKCS12
openssl pkcs12 -in my_in_file.p12 -nokeys -out my_out_file.cer.pem
openssl pkcs12 -in my_in_file.p12 -nodes -nocerts -out my_out_file.key.pem