org.locationtech.jts.io.geojson.GeoJsonReader Maven / Gradle / Ivy
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.io.geojson;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.json.simple.parser.JSONParser;
import org.locationtech.jts.geom.CoordinateSequence;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LineString;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.Polygon;
import org.locationtech.jts.geom.PrecisionModel;
import org.locationtech.jts.geom.impl.CoordinateArraySequence;
import org.locationtech.jts.io.ParseException;
/**
* Reads a GeoJson Geometry from a JSON fragment into a {@link Geometry}.
*
* A specification of the GeoJson format can be found at the GeoJson web site:
* http://geojson.org/geojson-spec.html.
*
* It is the caller's responsibility to ensure that the supplied
* {@link PrecisionModel} matches the precision of the incoming data. If a lower
* precision for the data is required, a subsequent process must be run on the
* data to reduce its precision.
*
* @author Martin Davis
* @author Paul Howells, Vivid Solutions.
*
*/
public class GeoJsonReader {
private GeometryFactory gf;
/**
* The default constructor uses the SRID from the Geojson CRS and the
* default PrecisionModel to create a
* GeometryFactory. If there is no CRS specified then the default
* CRS is a geographic coordinate reference system, using the WGS84 datum, and
* with longitude and latitude units of decimal degrees (SRID = 4326)
*/
public GeoJsonReader() {
// do nothing
}
/**
* This constructor accepts a GeometryFactory that is used
* to create the output geometries and to override the GeoJson CRS.
*
* @param geometryFactory
* a GeometryFactory
*/
public GeoJsonReader(GeometryFactory geometryFactory) {
this.gf = geometryFactory;
}
/**
* Reads a GeoJson Geometry from a String into a single
* {@link Geometry}.
*
*
* @param json
* The GeoJson String to parse
* @return the resulting JTS Geometry
*
* @throws ParseException
* throws a ParseException if the JSON string cannot be parsed
*/
public Geometry read(String json) throws ParseException {
Geometry result = read(new StringReader(json));
return result;
}
/**
* Reads a GeoJson Geometry from a {@link Reader} into a single
* {@link Geometry}.
*
*
* @param reader
* The input source
* @return The resulting JTS Geometry
*
* @throws ParseException
* throws a ParseException if the JSON string cannot be parsed
*/
public Geometry read(Reader reader) throws ParseException {
Geometry result = null;
JSONParser parser = new JSONParser();
try {
@SuppressWarnings("unchecked")
Map geometryMap = (Map) parser
.parse(reader);
GeometryFactory geometryFactory = null;
if (this.gf == null) {
geometryFactory = this.getGeometryFactory(geometryMap);
} else {
geometryFactory = this.gf;
}
result = create(geometryMap, geometryFactory);
} catch (org.json.simple.parser.ParseException e) {
throw new ParseException(e);
} catch (IOException e) {
throw new ParseException(e);
}
return result;
}
private Geometry create(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
String type = (String) geometryMap.get(GeoJsonConstants.NAME_TYPE);
if (type == null) {
throw new ParseException(
"Could not parse Geometry from Json string. No 'type' property found.");
} else {
if (GeoJsonConstants.NAME_POINT.equals(type)) {
result = createPoint(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_LINESTRING.equals(type)) {
result = createLineString(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_POLYGON.equals(type)) {
result = createPolygon(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_MULTIPOINT.equals(type)) {
result = createMultiPoint(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_MULTILINESTRING.equals(type)) {
result = createMultiLineString(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_MULTIPOLYGON.equals(type)) {
result = createMultiPolygon(geometryMap, geometryFactory);
} else if (GeoJsonConstants.NAME_GEOMETRYCOLLECTION.equals(type)) {
result = createGeometryCollection(geometryMap, geometryFactory);
} else {
throw new ParseException(
"Could not parse Geometry from GeoJson string. Unsupported 'type':"
+ type);
}
}
return result;
}
private Geometry createGeometryCollection(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List> geometriesList = (List>) geometryMap
.get(GeoJsonConstants.NAME_GEOMETRIES);
Geometry[] geometries = new Geometry[geometriesList.size()];
int i = 0;
for (Map map : geometriesList) {
geometries[i] = this.create(map, geometryFactory);
++i;
}
result = geometryFactory.createGeometryCollection(geometries);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse GeometryCollection from GeoJson string.", e);
}
return result;
}
private Geometry createMultiPolygon(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List>>> polygonsList = (List>>>) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
Polygon[] polygons = new Polygon[polygonsList.size()];
int p = 0;
for (List>> ringsList : polygonsList) {
List rings = new ArrayList();
for (List> coordinates : ringsList) {
rings.add(createCoordinateSequence(coordinates));
}
if (rings.isEmpty()) {
continue;
}
LinearRing outer = geometryFactory.createLinearRing(rings.get(0));
LinearRing[] inner = null;
if (rings.size() > 1) {
inner = new LinearRing[rings.size() - 1];
for (int i = 1; i < rings.size(); i++) {
inner[i - 1] = geometryFactory.createLinearRing(rings.get(i));
}
}
polygons[p] = geometryFactory.createPolygon(outer, inner);
++p;
}
result = geometryFactory.createMultiPolygon(polygons);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse MultiPolygon from GeoJson string.", e);
}
return result;
}
private Geometry createMultiLineString(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List>> linesList = (List>>) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
LineString[] lineStrings = new LineString[linesList.size()];
int i = 0;
for (List> coordinates : linesList) {
lineStrings[i] = geometryFactory
.createLineString(createCoordinateSequence(coordinates));
++i;
}
result = geometryFactory.createMultiLineString(lineStrings);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse MultiLineString from GeoJson string.", e);
}
return result;
}
private Geometry createMultiPoint(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List> coordinatesList = (List>) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
CoordinateSequence coordinates = this
.createCoordinateSequence(coordinatesList);
result = geometryFactory.createMultiPoint(coordinates);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse MultiPoint from GeoJson string.", e);
}
return result;
}
private Geometry createPolygon(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List>> ringsList = (List>>) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
List rings = new ArrayList();
for (List> coordinates : ringsList) {
rings.add(createCoordinateSequence(coordinates));
}
if (rings.isEmpty()) {
throw new IllegalArgumentException("Polygon specified with no rings.");
}
LinearRing outer = geometryFactory.createLinearRing(rings.get(0));
LinearRing[] inner = null;
if (rings.size() > 1) {
inner = new LinearRing[rings.size() - 1];
for (int i = 1; i < rings.size(); i++) {
inner[i - 1] = geometryFactory.createLinearRing(rings.get(i));
}
}
result = geometryFactory.createPolygon(outer, inner);
} catch (RuntimeException e) {
throw new ParseException("Could not parse Polygon from GeoJson string.",
e);
}
return result;
}
private Geometry createLineString(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List> coordinatesList = (List>) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
CoordinateSequence coordinates = createCoordinateSequence(coordinatesList);
result = geometryFactory.createLineString(coordinates);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse LineString from GeoJson string.", e);
}
return result;
}
private Geometry createPoint(Map geometryMap,
GeometryFactory geometryFactory) throws ParseException {
Geometry result = null;
try {
@SuppressWarnings("unchecked")
List coordinateList = (List) geometryMap
.get(GeoJsonConstants.NAME_COORDINATES);
CoordinateSequence coordinate = this.createCoordinate(coordinateList);
result = geometryFactory.createPoint(coordinate);
} catch (RuntimeException e) {
throw new ParseException("Could not parse Point from GeoJson string.", e);
}
return result;
}
private GeometryFactory getGeometryFactory(Map geometryMap)
throws ParseException {
GeometryFactory result = null;
@SuppressWarnings("unchecked")
Map crsMap = (Map) geometryMap.get(GeoJsonConstants.NAME_CRS);
Integer srid = null;
if (crsMap != null) {
try {
@SuppressWarnings("unchecked")
Map propertiesMap = (Map) crsMap
.get(GeoJsonConstants.NAME_PROPERTIES);
String name = (String) propertiesMap.get(GeoJsonConstants.NAME_NAME);
String[] split = name.split(":");
String epsg = split[1];
srid = Integer.valueOf(epsg);
} catch (RuntimeException e) {
throw new ParseException(
"Could not parse SRID from Geojson 'crs' object.", e);
}
}
if (srid == null) {
// The default CRS is a geographic coordinate reference
// system, using the WGS84 datum, and with longitude and
// latitude units of decimal degrees. SRID 4326
srid = Integer.valueOf(4326);
}
result = new GeometryFactory(new PrecisionModel(), srid.intValue());
return result;
}
private CoordinateSequence createCoordinateSequence(
List> coordinates) {
CoordinateSequence result = null;
result = new CoordinateArraySequence(coordinates.size());
for (int i = 0; i < coordinates.size(); ++i) {
List ordinates = coordinates.get(i);
if (ordinates.size() > 0) {
result.setOrdinate(i, 0, ordinates.get(0).doubleValue());
}
if (ordinates.size() > 1) {
result.setOrdinate(i, 1, ordinates.get(1).doubleValue());
}
if (ordinates.size() > 2) {
result.setOrdinate(i, 2, ordinates.get(2).doubleValue());
}
}
return result;
}
private CoordinateSequence createCoordinate(List ordinates) {
CoordinateSequence result = new CoordinateArraySequence(1);
if (ordinates.size() > 0) {
result.setOrdinate(0, 0, ordinates.get(0).doubleValue());
}
if (ordinates.size() > 1) {
result.setOrdinate(0, 1, ordinates.get(1).doubleValue());
}
if (ordinates.size() > 2) {
result.setOrdinate(0, 2, ordinates.get(2).doubleValue());
}
return result;
}
}