SimpleFeatureType schema = featureSource.getSchema();
CoordinateReferenceSystem crs = schema.getCoordinateReferenceSystem();
ReferencedEnvelope bounds = featureSource.getBounds();
MapContext context = new DefaultMapContext(crs);
Style style = new BasicPolygonStyle();
context.addLayer(featureSource, style);
context.setAreaOfInterest(bounds);
StreamingRenderer renderer = new StreamingRenderer();
renderer.setContext(context);