private void setProtocols(String protocolsString, boolean append) {
    List<Protocol> protocolsList = new ArrayList<>();
    if (append) {
      protocolsList.addAll(client.getProtocols());
    }
    for (String protocol : protocolsString.split(",", -1)) {
      try {
        protocolsList.add(Protocol.get(protocol));
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
    client.setProtocols(protocolsList);
  }
Returns true if either:
<ul>
  <li>A specific proxy was explicitly configured for this connection.
  <li>The response has already been retrieved, and a proxy was {@link
      java.net.ProxySelector selected} in order to get it.
</ul>

<p><strong>Warning:</strong> This method may return false before attempting
to connect and true afterwards.
gateway/platforms/servlet/src/main/java/io/apiman/gateway/platforms/servlet/connectors/ok/HttpURLConnectionImpl.java