基于GeoTools的WMS设计与实现
GeoTools是一个Java软件包地理实现。
WMS是一种服务设计理念。
由上图可见，后端一共有三个函数GetCapabilities、GetMap和GetFeatureInfo，根据接收到的客户端的参数来分别进行调用。并将结果返回给客户端，WMS一般是返回图像格式的文件。
基于GeoTools的WMS的设计与实现，可以直接看GeoServer，它就是基于GeoTools的WMS实现。而且还包含了Jetty服务器，可以直接使用。当然也可以使用War包版本，放在Tomcat服务器下面。
第一步：拦截请求参数
public void doService(HttpServletRequest request,
HttpServletResponse response) throws IOException {
Map map = request.getParameterMap();
Map param = new HashMap();
for (String k : map.keySet()) {
String s1 = "";
if (param.containsKey(k.toUpperCase())) {
s1 = param.get(k.toUpperCase()) + ",";
}
String[] s2 = (String[]) map.get(k);
for (int i = 0; i < s2.length; i++) {
s1 += s2[i] + (i == 0 ? "" : ",");
}
param.put(k.toUpperCase(), s1);
}
if (!param.containsKey("REQUEST")) {
WMSException.exception(response);
} else {
String wmsRequest = param.get("REQUEST");
if (wmsRequest.equals("GetCapabilities")) {
GetCapabilitiesRequest gcr = new GetCapabilitiesRequest(param);
doGetCapabilities(gcr, response);
} else if (wmsRequest.equals("GetMap")) {
GetMapRequest gmr = new GetMapRequest(param);
doGetMap(gmr, response);
} else if (wmsRequest.equals("GetFeatureInfo")) {
GetFeatureInfoRequest gfr = new GetFeatureInfoRequest(param);
doGetFeatureInfo(gfr, response);
} else {
WMSException.exception(response);
}
}
}
第二步：
private static void addShapeLayer(String name) throws Exception {
File file = new File("C:\data\" + name + ".shp");
File sldFile = new File("C:\data\" + name + ".sld");
FileDataStore store = FileDataStoreFinder.getDataStore(file);
((ShapefileDataStore) store).setStringCharset(Charset.forName("GB2312"));
FeatureSource featureSource = store
.getFeatureSource();
Configuration config = new SLDConfiguration();
Parser parser = new Parser(config);
InputStream sld = new FileInputStream(sldFile);
StyledLayerDescriptor styleSLD = (StyledLayerDescriptor) parser.parse(sld);
Style style = SLD.defaultStyle(styleSLD);
map.addLayer(featureSource, style);
}
第三步：
private void doGetMap(GetMapRequest gmr, HttpServletResponse response)
throws IOException {
double x1, y1, x2, y2;
int width, height;
try {
x1 = Double.parseDouble(gmr.getBBOX()[0]);
y1 = Double.parseDouble(gmr.getBBOX()[1]);
x2 = Double.parseDouble(gmr.getBBOX()[2]);
y2 = Double.parseDouble(gmr.getBBOX()[3]);
width = Integer.parseInt(gmr.getWidth());
height = Integer.parseInt(gmr.getHeight());
} catch (Exception e) {
WMSException.exception(response);
return;
}
// 设置输出范围
ReferencedEnvelope mapArea = new ReferencedEnvelope(x1, x2, y1, y2, crs);
// 初始化渲染器
StreamingRenderer sr = new StreamingRenderer();
sr.setContext(map);
// 初始化输出图像
BufferedImage bi = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);
Graphics g = bi.getGraphics();
((Graphics2D) g).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
((Graphics2D) g).setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
Rectangle rect = new Rectangle(0, 0, width, height);
// 绘制地图
sr.paint((Graphics2D) g, rect, mapArea);
// 编码图像
PNGEncodeParam encodeParam = PNGEncodeParam.getDefaultEncodeParam(bi);
if (encodeParam instanceof PNGEncodeParam.Palette) {
PNGEncodeParam.Palette p = (PNGEncodeParam.Palette) encodeParam;
byte[] b = new byte[] { -127 };
p.setPaletteTransparency(b);
}
//将图像数据输出到Servlet相应中
response.setContentType("image/png");
ServletOutputStream out = response.getOutputStream();
com.sun.media.jai.codec.ImageEncoder encoder = ImageCodec
.createImageEncoder("PNG", out, encodeParam);
encoder.encode(bi.getData(), bi.getColorModel());
bi.flush();
}
第四步：
private void doGetFeatureInfo(GetFeatureInfoRequest gfr,
HttpServletResponse response) throws IOException {
double x1, y1, x2, y2;
int width, height, i, j;
try {
x1 = Double.parseDouble(gfr.getBBOX()[0]);
y1 = Double.parseDouble(gfr.getBBOX()[1]);
x2 = Double.parseDouble(gfr.getBBOX()[2]);
y2 = Double.parseDouble(gfr.getBBOX()[3]);
width = Integer.parseInt(gfr.getWidth());
height = Integer.parseInt(gfr.getHeight());
i = Integer.parseInt(gfr.getI());
j = Integer.parseInt(gfr.getJ());
} catch (Exception e) {
WMSException.exception(response);
return;
}
// 计算点选范围的地图坐标
double cx1, cy1, cx2, cy2;
cx1 = x1 * (width - i + 0.5 + GET_FEATURE_INFO_BUFFUR) / width + x2
* (i - 0.5 - GET_FEATURE_INFO_BUFFUR) / width;
cx2 = x1 * (width - i + 0.5 - GET_FEATURE_INFO_BUFFUR) / width + x2
* (i - 0.5 + GET_FEATURE_INFO_BUFFUR) / width;
cy1 = y1 * (j - 0.5 + GET_FEATURE_INFO_BUFFUR) / height + y2
* (height - j + 0.5 - GET_FEATURE_INFO_BUFFUR) / height;
cy2 = y1 * (j - 0.5 - GET_FEATURE_INFO_BUFFUR) / height + y2
* (height - j + 0.5 + GET_FEATURE_INFO_BUFFUR) / height;
ReferencedEnvelope clickArea = new ReferencedEnvelope(cx1, cx2, cy1, cy2, crs);
MapLayer[] maplayers = map.getLayers();
FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2(null);
response.setContentType("text/html");
response.setCharacterEncoding("GBK");
PrintWriter out = response.getWriter();
out.println("location: " + ((cx1 + cx2) / 2.0) + ", "
+ ((cy1 + cy2) / 2.0) + "<br/>");
// 分别在每个图层中查找点选范围内的对象
for (int k = 0; k < maplayers.length; k++) {
FeatureSource fs =
(FeatureSource) maplayers[k].getFeatureSource();
String geometryPropertyName = fs.getSchema().getGeometryDescriptor().getLocalName();
Filter filter = ff.bbox(ff.property(geometryPropertyName), clickArea);
FeatureCollection fc = fs.getFeatures(filter);
SimpleFeatureType schema = fc.getSchema();
FeatureIterator fi = fc.features();
if (fi.hasNext()) {
out.println("Selected feature(s) in layer ["+schema.getTypeName()+"]:<br/>");
while (fi.hasNext()) {
SimpleFeature f = fi.next();
out.println("id:" + f.getID() + "<br/>");
for (AttributeDescriptor type : schema
.getAttributeDescriptors()) {
String name = type.getLocalName();
if (!name.equals(geometryPropertyName))
out.println(name + ":"
+ f.getProperty(name).getValue().toString()
+ "<br/>");
}
out.println("<br/>");
}
}
}
out.flush();
out.close();
}