title: Forward REMOTE_USER to tomcat via AJP (e.g. for shibboleth)
body: <p>Today I just got stuck with the following problem:
  1. I configured apache for basic authentication (require valid user); which worked.
  2. I further configured apache to forward requests for some path (/idp in my case) to a tomcat servlet (shibboleth IDP).</p>
  
  <p>The result was, that the shibboleth IdP (ECP profile) told me there was no "REMOTE_USER" set (it's using the httpRequest.getRemoteUser() method to check this; it returned null).</p>
  
  <p>I tried a lot of things like SetEnv and RewriteRule stuff, but without success.</p>
  
  <p>The solution is quite simple, but rather hard to find... so I decided to post it here to help others solving that kind of issue.</p>
  
  <p>Regards
  Stefan</p>