How do I forward requests to another URL without actually changing the URL in Apache?

Question

I have Apache running in a domain, for example http://example.com. I also have Tomcat running on my server and I've forwarded all requests made to http://example.com/t/ to Tomcat and all other URLs are served by Apache directly.

My problem is I have a URL like http://example.com/bar, but it should actually point to http://example.com/t/bar.

In other words, the URL should be processed by Tomcat which gets the application context "bar".

Problem is, I'm not quite sure how to make the proper rewrite rule for this. I tried adding this to sites-available/default

RewriteEngine on
RewriteRule ^/bar(.*) /t/bar$1 [R]

But that doesn't preserve the URL, and instead just redirects to the Tomcat URL with the /t/ prefix. If I remove the [R], then I just get a 404.

What is the proper RewriteRule to solve my problem?

Answer 1

You should use the 'P' (proxy) option on the mod_rewrite rule to be done internally to the server. You will also need to enable mod_proxy.

from the mod_rewrite docs:

'proxy|P' (force proxy)

This flag forces the substitution part to be internally sent as a proxy request and immediately (rewrite processing stops here) put through the proxy module. You must make sure that the substitution string is a valid URI (typically starting with http://hostname) which can be handled by the Apache proxy module. If not, you will get an error from the proxy module. Use this flag to achieve a more powerful implementation of the ProxyPass directive, to map remote content into the namespace of the local server.

Note: mod_proxy must be enabled in order to use this flag.