code: private String[] getServerLayerIds(MapModel mapModel) {
  		List<String> layerIds = new ArrayList<String>();
  		for (Layer<?> layer : mapModel.getLayers()) {
  			if (layer.isShowing()) {
  				layerIds.add(layer.getServerLayerId());
  			}
  		}
  		return layerIds.toArray(new String[layerIds.size()]);
  	}
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