I have a JavaEE appliation to serve tiles generated dynamically by geotools
using GTRenderer, for example, for a given request:
*http://localhost/tile/z/x/y.png?layers=road,river
<http://localhost/tile/z/x/y.png?layers=road,river>*
I will calculate the boundingbox of the request area and call GTRenderer to
render the image, here are the two main class:
ImageProvider(generate the images):
*public class ImageProvider {*
* private Map<String, Style> styles = new HashMap<String, Style>();*
* private String sld;*
* private GTRenderer renderer = new StreamingRenderer();*
* //style*
* StyleFactory styleFactory = CommonFactoryFinder.getStyleFactory();*
* CoordinateReferenceSystem crs;*
* private void init() {*
* System.setProperty("org.geotools.referencing.forceXY", "true");*
* try {*
* SLDParser stylereader = new SLDParser(styleFactory,
ImageProvider.class.getResource(this.sld));*
* Style[] ss = stylereader.readXML();*
* for (Style s : ss) {*
* styles.put(s.getName(), s);*
* }*
* crs = CRS.decode("EPSG:4326");*
* } catch (Exception e) {*
* throw new RuntimeException(e.getMessage());*
* } *
* }*
* @Override*
* public ArrayList<BufferedImage> render(Coord coordinate, int width, int
height, MapLayer... layers) {*
* double[] box = Util.getBoundingBox(coordinate.x, coordinate.y,
coordinate.zoom);*
* ReferencedEnvelope bbox = new ReferencedEnvelope(box[0], box[2], box[1],
box[3], crs);*
* Rectangle imageSize = new Rectangle(0, 0, width, height);*
* ArrayList<BufferedImage> result = new ArrayList<BufferedImage>();*
* for (MapLayer layer : layers) {*
* BufferedImage cachedTileData = null;*
* //render for current layer*
* BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);*
* Graphics2D g = image.createGraphics();*
* //set transparent*
* g.setComposite(AlphaComposite.Clear);*
* g.fillRect(0, 0, width, height);*
* g.setComposite(AlphaComposite.Src);*
* MapContent mapContent = new MapContent();*
* try {*
* String schemaName = layer.dataStore.getSchema().getName().toString(); //*
* Style style = styles.get(schemaName);*
* mapContent.addLayer(new FeatureLayer(layer.dataStore.getFeatureSource(),
style));*
* renderer.setMapContent(mapContent);*
* renderer.paint(g, imageSize, bbox);*
* } catch (IOException e) {*
* continue;*
* } finally {*
* mapContent.dispose();*
* g.dispose();*
* }*
* result.add(image);*
* }*
* return result;*
* }*
*}*
And The servlet:
*public class ImageServlet extends HttpServlet {*
* private ImageProvider imageProvider;*
* @Override*
* public void init() throws ServletException {*
* super.init();*
* //image provider initialization codes omitted*
* }*
* @Override*
* protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException {*
* Coord coord=parseCoord(req);*
* String format=parseFormat(req);*
* String layers = req.getParameter("layer");*
* ArrayList<BufferedImage> tileResponse = imageProvider.render(coord, 256,
256, format, layers.split(","));*
* if (tileResponse != null) {*
* //save images to response*
* }*
* }*
* @Override*
* protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {*
* doGet(req, resp);*
* }*
*}*
You may find that I made the `GTRenderer` as a field in the class
`ImageProvider`, since I found that it will cost almost 500+ milliseconds
to create a new instanc of `StreamingRenderer`.
However I found the `StreamingRenderer` is not thread safe:
http://docs.geotools.org/stable/javadocs/org/geotools/renderer/lite/StreamingRenderer.html
It seems that I have to synchronize the `StreamingRenderer` field, but if
so I am afraid the performance.
So I wonder if there is any good idea to make an accept performance ?
BTW, I am new in geotools, so if you found any un-proper usage of geotools,
please let me know. :)
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