@Override
  protected void initTarget() throws ServletException {
    targetUriTemplate = getConfigParam(P_TARGET_URI);
    if (targetUriTemplate == null)
      throw new ServletException(P_TARGET_URI+" is required.");

    //leave this.target* null to prevent accidental mis-use
  }
A proxy servlet in which the target URI is templated from incoming request parameters. The
format adheres to the <a href="http://tools.ietf.org/html/rfc6570">URI Template RFC</a>, "Level
1". Example:
<pre>
  targetUri = http://{host}:{port}/{path}
</pre>
--which has the template variables.  The incoming request must contain query args of these
names.  They are removed when the request is sent to the target.
src/main/java/org/mitre/dsmiley/httpproxy/URITemplateProxyServlet.java