How to redirect http requests to https in apache

　DocumentRoot /var/www/html
　ServerName samtz.dyndns.org
　ErrorLog logs/samtz-error_log
　CustomLog logs/samtz-access_log combined
　
　　Options ExecCGI
　　Options Indexes
　　AllowOverride All
　
　RewriteEngine on
　RewriteCond %{SERVER_PORT} =80
　RewriteRule ^(.*) https://%{SERVER_NAME}%{REQUEST_URI}