title: Adding an HTTP Header to the request in a servlet filter
body: <p>I'm integrating with an existing servlet that pulls some properties out of the HTTP header.  Basically, I'm implementing an interface that doesn't have access to the actual request, it just has access to a map of k->v for the HTTP headers.</p>
  
  <p>I need to pass in a request parameter.  The plan is to use a servlet filter to go from parameter to header value but of course the HttpServletRequest object doesn't have an addHeader() method.</p>
  
  <p>Any ideas?</p>