Re-writing in the container

CustomResourceFilter.scala

package code.filter

import javax.servlet._
import http._
import java.util.regex._

// A wrapper around an HTTP Servlet Request which removes any /cached/:id from a URI
case class ResouceRequest(req: HttpServletRequest) extends HttpServletRequestWrapper(req) {

  // The URI without the /cached/:id part:
  lazy val rewritten: Option[String] = {
    val pattern = "^/cache/[^/]+(/.+)$".r
    pattern.findFirstMatchIn(req.getRequestURI).map(_.group(1))
  }

  // Lift (currently) uses the servlet getRequetURI, allowing us to jump in
  // and change the URI as far as Lift is concerned:
  override def getRequestURI(): String =
   rewritten getOrElse req.getRequestURI

}

class CustomResourceFilter extends Filter {

  def init(config: FilterConfig): Unit = {}

  def doFilter(
    request: ServletRequest,
    response: ServletResponse,
    chain: FilterChain): Unit = {

    // Containers can support non-HTTP requests, but we just pick out
    // the HTTP ones and re-write them:
    val rewritten = request match {
      case httpReq: HttpServletRequest => ResouceRequest(httpReq)
      case _ => request
    }

    // Pass our (possibly modified) request on to Lift:
    chain.doFilter(rewritten, response)
  }

  def destroy(): Unit = {}
}

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>

 <filter>
    <filter-name>CustomResourceFilter</filter-name>
    <display-name>Resource Filter</display-name>
    <description>sRemoves anti-caching path from URLs</description>
    <filter-class>code.filter.CustomResourceFilter</filter-class>
  </filter>

  <filter>
    <filter-name>LiftFilter</filter-name>
    <display-name>Lift Filter</display-name>
    <description>The Filter that intercepts lift calls</description>
    <filter-class>net.liftweb.http.LiftFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>CustomResourceFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

  <filter-mapping>
    <filter-name>LiftFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

</web-app>