JSESSIONID not perssist

I have an server where run an Tomcat Server with an Java App.
Besides run also an Apache2 Server which work as reverse proxy where I had set 2 VirtualHosts.

#HTTP(www/non-www) -> HTTPS(non-www)
<VirtualHost *:80>

   ServerName mydom.com
   ServerAlias www.mydom.com

   Redirect permanent / https://mydom.com/

</VirtualHost>

#ACTIVATE HTTPS AND REVERSE PROXY -> myapp
<VirtualHost *:443>

   SSLEngine On

   SSLCertificateFile /opt/ssl/new/mydom.crt
   SSLCertificateKeyFile /opt/ssl/new/mydom.key
   SSLCertificateChainFile /opt/ssl/new/mydom.ca-bundle

   BrowserMatch ".*MSIE.*" nokeepalive ssl-unclean-shutdown downgrade-1.0 force-response-1.0
   SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL

   ServerName mydom.com
   ServerAlias www.mydom.com

   ProxyRequests Off
   ProxyPreserveHost On
   ProxyPass / http://127.0.0.1:8080/myapp/
   ProxyPassReverse / http://127.0.0.1:8080/myapp/

</VirtualHost>

Code (ApacheConf):

My problem is that session not persist between requests. At every request session have another id.

I test this it with this:

@Controller
@RequestMapping(value = "/sess")
public class TestSession{

    @RequestMapping(method = RequestMethod.GET)
    public void mainPage(HttpServletRequest request, HttpServletResponse response) throws IOException{

        HttpSession session = request.getSession();

        response.setContentType("text/html");
        response.getWriter().println(session.getId());

    }

}

Code (markup):

I access it like this: mydom.com/sess and on page is printed id of session.

In first phase I thought is a problem at my app.
But I tested it on localhost on my PC and everything works. Session persist.

After a while I found the problem is at how I access my app.
If I put in url bar https:// mydom.com/sess, session persist. If I put only mydom.com/sess(redirect to https), session not persist.

How I can fix that?