/**
   * Create a layer described by an XML layer description.
   *
   * @param domElement the XML element describing the layer to create.
   * @param params any parameters to apply when creating the layer.
   * @return a new layer
   * @throws WWUnrecognizedException if the layer type or service type given in the describing
   *     element is unrecognized.
   * @see #createTiledImageLayer(org.w3c.dom.Element, gov.nasa.worldwind.avlist.AVList).
   */
  protected Layer createFromLayerDocument(Element domElement, AVList params) {
    String className = WWXML.getText(domElement, "@className");
    if (className != null && className.length() > 0) {
      Layer layer = (Layer) WorldWind.createComponent(className);
      String actuate = WWXML.getText(domElement, "@actuate");
      layer.setEnabled(WWUtil.isEmpty(actuate) || actuate.equals("onLoad"));
      WWXML.invokePropertySetters(layer, domElement);
      return layer;
    }

    AVList props = WWXML.copyProperties(domElement, null);
    if (props != null) { // Copy params and add any properties for this layer to the copy
      if (params != null) props.setValues(params);
      params = props;
    }

    Layer layer;
    String href = WWXML.getText(domElement, "@href");
    if (href != null && href.length() > 0) {
      Object o = this.createFromConfigSource(href, params);
      if (o == null) return null;

      if (!(o instanceof Layer)) {
        String msg =
            Logging.getMessage("LayerFactory.UnexpectedTypeForLayer", o.getClass().getName());
        throw new WWRuntimeException(msg);
      }

      layer = (Layer) o;
    } else {
      String layerType = WWXML.getText(domElement, "@layerType");
      if (layerType != null && layerType.equals("TiledImageLayer")) {
        layer = this.createTiledImageLayer(domElement, params);
      } else {
        String msg = Logging.getMessage("generic.UnrecognizedLayerType", layerType);
        throw new WWUnrecognizedException(msg);
      }
    }

    if (layer != null) {
      String actuate = WWXML.getText(domElement, "@actuate");
      layer.setEnabled(actuate != null && actuate.equals("onLoad"));
      WWXML.invokePropertySetters(layer, domElement);
    }

    return layer;
  }
  /**
   * Determines and stores the network sites to test for public network connectivity. The sites are
   * drawn from the JVM's gov.nasa.worldwind.avkey.NetworkStatusTestSites property ({@link
   * AVKey#NETWORK_STATUS_TEST_SITES}). If that property is not defined, the sites are drawn from
   * the same property in the World Wind or application configuration file. If the sites are not
   * specified there, the set of sites specified in {@link #DEFAULT_NETWORK_TEST_SITES} are used. To
   * indicate an empty list in the JVM property or configuration file property, specify an empty
   * site list, "".
   */
  protected void establishNetworkTestSites() {
    String testSites = System.getProperty(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null)
      testSites = Configuration.getStringValue(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null) {
      this.networkTestSites.addAll(Arrays.asList(DEFAULT_NETWORK_TEST_SITES));
    } else {
      String[] sites = testSites.split(",");
      List<String> actualSites = new ArrayList<String>(sites.length);

      for (String site : sites) {
        site = WWUtil.removeWhiteSpace(site);
        if (!WWUtil.isEmpty(site)) actualSites.add(site);
      }

      this.setNetworkTestSites(actualSites);
    }
  }