If you've got another web application running on your server, but still want it served up on port 80 or 443 you can use Apache's mod_proxy to forward traffic from Apache to your application.

An example would be if your web application is running on http://localhost:8080 you can use Apache to redirect traffic from http://service.yourdomain.com to that web app. Simply create a new configuration file for Apache under /etc/httpd/conf.d with the following:

# Put this after the other LoadModule directives
LoadModule proxy_module /usr/lib/apache2/modules/mod_proxy.so  
LoadModule proxy_http_module /usr/lib/apache2/modules/mod_proxy_http.so

# Put this with your other VirtualHosts, or at the bottom of the file
NameVirtualHost *  
<VirtualHost *:80>  
    ServerName service.yourdomain.com

    ProxyRequests Off
    <Proxy *>
        Order deny,allow
        Allow from all
    </Proxy>

    ProxyPass / http://127.0.0.1:8080/
    ProxyPassReverse / http://127.0.0.1:8080/
    <Location />
        Order allow,deny
        Allow from all
    </Location>
</VirtualHost>  

Restart Apache and you should be good to go.

systemctl restart httpd