code: public static String styleToString( Style style ) throws Exception {
          StyledLayerDescriptor sld = sf.createStyledLayerDescriptor();
          UserLayer layer = sf.createUserLayer();
          layer.setLayerFeatureConstraints(new FeatureTypeConstraint[]{null});
          sld.addStyledLayer(layer);
          layer.addUserStyle(style);
  
          SLDTransformer aTransformer = new SLDTransformer();
          aTransformer.setIndentation(4);
          String xml = aTransformer.transform(sld);
          return xml;
      }
docs: Converts a style to its string representation to be written to file.
  
  @param style the style to convert.
  @return the style string.
  @throws Exception