geotools最短路径的实现

Geotools提供了一个Graph的扩展包，使用它可以实现最短路径的查找，提供的算法有和AStar。Api的功能非常强大，只需要提供line的features对象，即可创建graph, 然后调用算法即可实现最短路径查找，权重可以自由设置，对于不懂算法的人用起来也毫不费力的使用。

String filePath = "E:\\gis资料|\测试数据\\道路中心线.shp";
//读取shp数据
DataStore dataStore = readShapeFile (filePath);
SimpleFeatureSource featureSource = dataStore.getFeatureSource(dataStore.getTypeNames0[0]);
SimpleFeatureCollection simFeatureCollect =featureSource.getFeatures();
final Integer num = new Integer(0);
System.out.printn("shp文件原始线的个数: " + simFeatureCollect.size();
//创建graph数据结构
Graph graph = buildGraph (simFeatureCollect);

//这里是定义权重
Dijkstralterator .EdgeWeighter weighter = new Djkstralterator .EdgeWeighter({
@Override
public double getWeight(Edge edge) {
//这个方法返回的值就是权重，这里使用的最简单的线的长度
//如果有路况、限速等信息，可以做的更复杂- -些
SimpleFeature feature = (SimpleFeature)edge.getObject();
Geometry geometry = (Geometry)feature.getDefaultGeometry(;
return geometry.getL .ength();
Date startT = new Date();

//初始化查找器
DijkstraShortestPathFinder pf = new DjkstraShortestPathFinder(graph,start,weighter);
pf.calculate();
//传入终点，得到最短路径
Path path = pf.getPath(destination);
Date end = new Date();
System.out. printIn("迪杰斯特拉算法耗时: " +(end.getTime() - startT.getTime());
System.out. println("迪杰斯特拉算法距离: "+getPathL ength (path);
System.out. printIn(destination.getID(0+"+start.equals(destination));

//AStar算法

public static void AStarShortestPath(Graph graph,Node startNode,Node endNode){
AStarlterator .AStarFunctions aStarFunction = new AStarlterator .AStarFunctions(endNode){
@Override
public double cost(AStarlterator.AStarNode aStarNode, AStarlterator.AStarNode aStarNode1) {
Edge edge = aStarNode.getNode0.getEdge(aStarNode 1.getNode();
SimpleFeature feature = (SimpleFeature)edge.getObject);
Geometry geometry = (Geometry)feature.getDefaultGeometry();
//System.out.printIn(aStarNode.getH0);
return geometry.getL ength();
@Override
public double h(Node node) {
return-10; .
};
Date start = new Date();
AStarShortestPathFinder aStarPf = new AStarShortestPathFinder(graph,startNode,endNode,aStarFunction);

try {
aStarPf.calculate();
Date end = new Date();
System.out.println("AStar算法耗时: " +(end.getTime() - start.getTime));
System.out.println("AStar算法距离: " + getPathL .ength(aStarPf.getPath0));
. } catch (Exceptione) {
e.printStackTrace();
}

AStar算法使用也很简单，可参考api使用文档。 两个算法效率比较下来，AStar算法效率更好。 算法验证和效率比较:
使用同样的起点和终点，分别调用上面两个算法，计算结果如下:
shp文件原始线段的个数: 67749
AStar算法耗时: 84ms
@
AStar距离: 0.2307215100346536

迪杰斯特拉耗时: 188ms
迪杰斯特拉距离: 0.2307215100346536 .

参考：https://wenku.baidu.com/view/f7f72108b7daa58da0116c175f0e7cd1842518aa.html

创建Graph方向图：https://www.cnblogs.com/help-silence/p/11872194.html（Geotools中读取shapefile路网数据，并创建DirectedGraph）

官方文档：https://docs.geotools.org/latest/userguide/extension/graph/