Rewrite subfolder to subdomain with Apache htaccess

Probably the ProxyPass / directive you have in your config routes all requests to the Tomcat backend, bypassing all your mod_rewrite directives. You can try to remove the ProxyPass directive and use RewriteRule with the [P] flag after your other rewrites:

• mod_rewrite: P|proxy

For the expire headers the situation is worse — in another similar question a solution was not found.

Option +FollowSymLinks would be needed for using mod_rewrite in .htaccess files; in your case it is not required, because you can put everything in the Apache config. Moving rules from config to .htaccess is pointless and can only make things slower. However, there is an important difference between .htaccess and the Apache config — in .htaccess patterns in RewriteRule are matched against relative filesystem paths (which never start with /), while in the VirtualHost context these patterns are matched against the URL path after the hostname, which always starts with /. Therefore at least one of your rules is incorrect:

RewriteRule ^content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

should be

RewriteRule ^/content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

(note the additional slash in the beginning).

Remember that when you make an HTTPS connection to https://domain2.org (which is really a connection to https://domain2.org:443), the order is roughly

1. Browser opens connection to IP on port 443
2. Apache looks for a VirtualHost matching the combination IP:443
3. In this case it finds the VirtualHost for domain1.org
4. Apache sends the SSL certificate associated with that VirtualHost (i.e. the cert for domain1.org)
5. [The rest of the SSL negotiation]
6. Browser sends its HTTP request headers, including the Host: header telling Apache what domain it thinks it's talking to.
7. If applicable, mod_rewrite processing of the HTTP request headers happens here.

i.e. when Apache decides which certificate to send, it hasn't yet received the information that mod_rewrite would use to do the redirect.

To get around this you'd need a single certificate that was valid for both domains. This could be either a wildcard certificate (if the situation is domain1.example.com and domain2.example.com, get a certificate for *.example.com), or you could try to get an SSL certificate with a Subject of "domain1.org", but a Subject Alternate Name of "domain2.org".

In either case you'd need to do the redirection in the main Apache config files - if it's in a .htaccess file in domain2.org's DocumentRoot, then requests that use domain1.org's VirtualHost will go to a different DocumentRoot directory, and won't ever see the file.