JTS(Geometry)

空间数据模型
(1)、JTS Geometry model 
(2)、ISO Geometry model (Geometry Plugin and JTS Wrapper Plugin)
GeoTools has two implementations of these interfaces:
Geometry Plugin a port of JTS 1.7 to the ISO Geometry interfaces

JTS Wrapper Plugin an implementation that delegates all the work to JTS

JTS包结构

系（linearref包）、计算交点（noding包）、几何图形操作（operation包）、平面图（planargraph包）、多边形化（polygnize包）、精度（precision）、工具（util包）

重点理解JTS Geometry model
(1) JTS提供了如下的空间数据类型
     Point     
     MultiPoint
     LineString     
     LinearRing  封闭的线条
     MultiLineString    多条线
     Polygon
     MultiPolygon         

     GeometryCollection  包括点，线，面

(2) 支持接口
Coordinate
   Coordinate（坐标）是用来存储坐标的轻便的类。它不同于点，点是Geometry的子类。不像模范Point的对象（包含额外的信息，例如一个信包，一个精确度模型和空间参考系统信息），Coordinate只包含纵座标值和存取方法。
Envelope(矩形)
   一个具体的类，包含一个最大和最小的x 值和y 值。
GeometryFactory
   GeometryFactory提供一系列的有效方法用来构造来自Coordinate类的Geometry对象。支持接口

package com.mapbar.geo.jts;

import org.geotools.geometry.jts.JTSFactoryFinder;

import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryCollection;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.LineString;
import com.vividsolutions.jts.geom.LinearRing;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.geom.Polygon;
import com.vividsolutions.jts.geom.MultiPolygon;
import com.vividsolutions.jts.geom.MultiLineString;
import com.vividsolutions.jts.geom.MultiPoint;
import com.vividsolutions.jts.io.ParseException;
import com.vividsolutions.jts.io.WKTReader;

/**  

 * Class GeometryDemo.java 

 * Description Geometry 几何实体的创建，读取操作

 * Company mapbar 

 * author Chenll E-mail: [email protected]

 * Version 1.0 

 * Date 2012-2-17 上午11:08:50

 */
public class GeometryDemo {

	private GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );
	
	/**
	 * create a point
	 * @return
	 */
	public Point createPoint(){
		Coordinate coord = new Coordinate(109.013388, 32.715519);
		Point point = geometryFactory.createPoint( coord );
		return point;
	}
	
	/**
	 * create a point by WKT
	 * @return
	 * @throws ParseException 
	 */
	public Point createPointByWKT() throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		Point point = (Point) reader.read("POINT (109.013388 32.715519)");
		return point;
	}
	
	/**
	 * create multiPoint by wkt
	 * @return
	 */
	public MultiPoint createMulPointByWKT()throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		MultiPoint mpoint = (MultiPoint) reader.read("MULTIPOINT(109.013388 32.715519,119.32488 31.435678)");
		return mpoint;
	}
	/**
	 * 
	 * create a line
	 * @return
	 */
	public LineString createLine(){
		Coordinate[] coords  = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
		LineString line = geometryFactory.createLineString(coords);
		return line;
	}
	
	/**
	 * create a line by WKT
	 * @return
	 * @throws ParseException
	 */
	public LineString createLineByWKT() throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		LineString line = (LineString) reader.read("LINESTRING(0 0, 2 0)");
		return line;
	}
	
	/**
	 * create multiLine 
	 * @return
	 */
	public MultiLineString createMLine(){
		Coordinate[] coords1  = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
		LineString line1 = geometryFactory.createLineString(coords1);
		Coordinate[] coords2  = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
		LineString line2 = geometryFactory.createLineString(coords2);
		LineString[] lineStrings = new LineString[2];
		lineStrings[0]= line1;
		lineStrings[1] = line2;
		MultiLineString ms = geometryFactory.createMultiLineString(lineStrings);
		return ms;
	}
	
	/**
	 * create multiLine by WKT
	 * @return
	 * @throws ParseException
	 */
	public MultiLineString createMLineByWKT()throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		MultiLineString line = (MultiLineString) reader.read("MULTILINESTRING((0 0, 2 0),(1 1,2 2))");
		return line;
	}
	
	/**
	 * create a polygon(多边形) by WKT
	 * @return
	 * @throws ParseException
	 */
	public Polygon createPolygonByWKT() throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		Polygon polygon = (Polygon) reader.read("POLYGON((20 10, 30 0, 40 10, 30 20, 20 10))");
		return polygon;
	}
	
	/**
	 * create multi polygon by wkt
	 * @return
	 * @throws ParseException
	 */
	public MultiPolygon createMulPolygonByWKT() throws ParseException{
		WKTReader reader = new WKTReader( geometryFactory );
		MultiPolygon mpolygon = (MultiPolygon) reader.read("MULTIPOLYGON(((40 10, 30 0, 40 10, 30 20, 40 10),(30 10, 30 0, 40 10, 30 20, 30 10)))");
		return mpolygon;
	}
	
	/**
	 * create GeometryCollection  contain point or multiPoint or line or multiLine or polygon or multiPolygon
	 * @return
	 * @throws ParseException
	 */
	public GeometryCollection createGeoCollect() throws ParseException{
		LineString line = createLine();
		Polygon poly =  createPolygonByWKT();
		Geometry g1 = geometryFactory.createGeometry(line);
		Geometry g2 = geometryFactory.createGeometry(poly);
		Geometry[] garray = new Geometry[]{g1,g2};
		GeometryCollection gc = geometryFactory.createGeometryCollection(garray);
		return gc;
	}
	
	/**
	 * create a Circle  创建一个圆，圆心(x,y) 半径RADIUS
	 * @param x
	 * @param y
	 * @param RADIUS
	 * @return
	 */
	public Polygon createCircle(double x, double y, final double RADIUS){
		final int SIDES = 32;//圆上面的点个数
	    Coordinate coords[] = new Coordinate[SIDES+1];
	    for( int i = 0; i < SIDES; i++){
	        double angle = ((double) i / (double) SIDES) * Math.PI * 2.0;
	        double dx = Math.cos( angle ) * RADIUS;
	        double dy = Math.sin( angle ) * RADIUS;
	        coords[i] = new Coordinate( (double) x + dx, (double) y + dy );
	    }
	    coords[SIDES] = coords[0];
	    LinearRing ring = geometryFactory.createLinearRing( coords );
	    Polygon polygon = geometryFactory.createPolygon( ring, null );
	    return polygon;
	}
	
	/**
	 * @param args
	 * @throws ParseException 
	 */
	public static void main(String[] args) throws ParseException {
		GeometryDemo gt = new GeometryDemo();
		Polygon p = gt.createCircle(0, 1, 2);
		//圆上所有的坐标(32个)
		Coordinate coords[] = p.getCoordinates();
		for(Coordinate coord:coords){
			System.out.println(coord.x+","+coord.y);
		}
	}
}