GeoTools应用-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

[java]
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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: Chenll@mapbar.com

* 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);

}
}
}