Apache rule to change / (slash) to _ (underscore)

I've set up an Apache HTTP server with VirtualHosts in front of a proprietary web server in the back. The backend server can only have one (1) level in its ID paths so the following public URLs:

http://public-server/path1/path2/path3?querystring-parameters

should be converted for the backend to:

http://internal-server/path1/path2/page/<path1>_<path2>_<path3>?querystring-parameters

Notice that there can be any number of path1, path2, path3, path4, .... and they should all (no matter if only 1 exis开发者_开发知识库ts or multiple) be concatenated with an underscore. Also notice that the querystring-parameters CAN contain '?', '/' and '_' so the rule should not alter the querystring in any way.

I've tried searching for solutions to this but can't figure out how to overcome the problem. Any suggestions?

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If you can come up some maximum number of possible paths, you can do something to this effect:

# This will work for up to 5 paths
RewriteRule /([^/]*)/?([^/]*)/?([^/]*)/?([^/]*)/?([^/]*) http://internal-server%{REQUEST_URI}$1_$2_$3_$4_$5 [L,QSA]

The /?([^/]*) can be added to the end as many times as you need, along with added the corresponding groups (_$6 ..) to the rewritten URL.

Unfortunately, there is not a way have a completely unknown number of paths, while at the same time use them in the rewritten URL. Also, the [QSA] flag will attach your querystring on to the forwarded URL, untouched.

Hope this helps.