How to extract a private key from a java keystore

extract_private-key.txt

#First save the key in a p.12 file
#The p.12 file is password protected it shall prompt you to key in a new password
#You shall require to also key in the keystore password
keytool -v -importkeystore -srckeystore /path/to/keystore.jks -srcalias <alias> -destkeystore /path/to/output.p12 -deststoretype PKCS12

#Use openssl to store the private-key in a .pem file
openssl pkcs12 -in /path/to/output.p12 -out /path/to/private-key.pem -nodes