I just switched topjavablogs and topsqlblogs to HTTPS. Certificate is provided by Let's Encrypt and I followed these steps: https://www.digitalocean.com/community/tutorials/how-to-secure-apache-with-let-s-encrypt-on-ubuntu-14-04. One thing is missing in the tutorial and that's that Let's Encrypt didn't add SSL configuration to Apache configuration file and you need add it manually (inside <VirtualHost *:443>):

    SSLEngine on
    SSLCertificateKeyFile /etc/letsencrypt/live/DOMAIN.com/privkey.pem
    SSLCertificateFile /etc/letsencrypt/live/DOMAIN.com/cert.pem
    SSLCertificateChainFile /etc/letsencrypt/live/DOMAIN.com/chain.pem