Mark mark = styleFactory.getCircleMark();
mark.setStroke(styleFactory.createStroke(filterFactory.literal(strokeColor), filterFactory.literal(2)));
mark.setFill(styleFactory.createFill(filterFactory.literal(fillColor)));
Graphic gr = styleFactory.createDefaultGraphic();
gr.graphicalSymbols().clear();
gr.graphicalSymbols().add(mark);
gr.setSize(filterFactory.literal(5));
/*
* Setting the geometryPropertyName arg to null signals that we want to