Geotools中Geometry对象与GeoJson的相互转换

maven依赖

<geotools.version>17.1</geotools.version><!-- for geotools begin -->        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-geojson</artifactId>            <version>${geotools.version}</version>        </dependency>        <!-- https://mvnrepository.com/artifact/org.geotools/gt-main -->        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-main</artifactId>            <version>${geotools.version}</version>        </dependency>        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-api</artifactId>            <version>${geotools.version}</version>        </dependency>        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-opengis</artifactId>            <version>${geotools.version}</version>        </dependency>        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-data</artifactId>            <version>${geotools.version}</version>        </dependency>        <dependency>            <groupId>org.geotools</groupId>            <artifactId>gt-referencing</artifactId>            <version>${geotools.version}</version>        </dependency>        <!--for geotools end-->

引用情况

import com.fasterxml.jackson.databind.ObjectMapper;import com.vividsolutions.jts.geom.*;import com.vividsolutions.jts.geom.Point;import com.vividsolutions.jts.io.ParseException;import com.vividsolutions.jts.io.WKTReader;import com.vividsolutions.jts.operation.linemerge.LineMerger;import org.geotools.data.DataUtilities;import org.geotools.feature.SchemaException;import org.geotools.feature.simple.SimpleFeatureBuilder;import org.geotools.geojson.feature.FeatureJSON;import org.geotools.geojson.geom.GeometryJSON;import org.geotools.geometry.jts.JTSFactoryFinder;import org.opengis.feature.simple.SimpleFeature;import org.opengis.feature.simple.SimpleFeatureType;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import org.springframework.util.StringUtils;import java.io.IOException;import java.io.StringReader;import java.io.StringWriter;import java.util.*;

Geometry的子类主要有Point, LineString和Polygon. 基本操作类似。所以此处以LineString为例说明

LineString–>geojson

// 由wkt字符串构造LineString对象WKTReader reader = new WKTReader( geometryFactory );LineString lineString = (LineString)reader.read("LINESTRING (254058.76074485347 475001.2186020431, 255351.04293761664 474966.9279243938)");// 设置保留6位小数，否则GeometryJSON默认保留4位小数GeometryJSON geometryJson = new GeometryJSON(6);StringWriter writer = new StringWriter();geometryJson.write(lineString, writer);System.out.println(writer.toString());writer.close();

geojson–>LineString

LineString lineString = (LineString) geometryJson.read(new StringReader("{\n" +                "                \"type\": \"LineString\",\n" +                "                \"coordinates\": [\n" +                "                    [\n" +                "                        120.6584555,\n" +                "                        30.45144\n" +                "                    ],\n" +                "                    [\n" +                "                        120.1654515,\n" +                "                        30.54848\n" +                "                    ]\n" +                "                ]\n" +                "            }"));

geojson还定义了带属性的Feature和表示Geometry对象集合的FeatureCollection，构造方法更加复杂，写两个示例备忘吧。

LineString转Feature

// geometry是必须的，其他属性可根据需求自定义，但是支持的类型有限，例如这个版本中double是不支持的，只支持floatfinal SimpleFeatureType TYPE = DataUtilities.createType("Link",                "geometry:LineString," + // <- the geometry attribute: Point type                        "gid:String," +   // <- a String attribute                        "direction:Integer," +   // a number attribute                        "orientation:Integer"        );SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(TYPE);GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();WKTReader reader = new WKTReader( geometryFactory );FeatureJSON fjson = new FeatureJSON();LineString lineString = (LineString)reader.read("LINESTRING (254058.76074485347 475001.2186020431, 255351.04293761664 474966.9279243938)");// 按照TYPE中声明的顺序为属性赋值就可以，其他方法我暂未尝试featureBuilder.add(lineString);featureBuilder.add("123456");featureBuilder.add(2);featureBuilder.add(0);SimpleFeature feature = featureBuilder.buildFeature(null);StringWriter writer = new StringWriter();fjson.writeFeature(feature, writer);System.out.println(writer.toString());

执行结果如下：

{“type”:”Feature”,”geometry”:{“type”:”LineString”,”coordinates”:[[254058.7607,475001.2186],[255351.0429,474966.9279]]},”properties”:{“gid”:”123456”,”direction”:2,”orientation”:0},”id”:”fid–5b8f258_15e04bda4b8_-8000”}

Feature转LineString

应该与GeometryJson中的方法类似，因暂未遇到此需求，就先空着吧。随缘。。。。

LineString转FeatureCollection

String[] WKTS = { "LINESTRING (255351.04293761664 474966.9279243938, 255529.29662365236 474272.4599921228)",                "LINESTRING (255529.29662365236 474272.4599921228, 256166.05830998957 473979.44920198264)"};final SimpleFeatureType TYPE = DataUtilities.createType("Link",                "geometry:LineString," + // <- the geometry attribute: Point type                        "gid:String," +   // <- a String attribute                        "direction:Integer," +   // a number attribute                        "orientation:Integer");SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(TYPE);GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();WKTReader reader = new WKTReader( geometryFactory );FeatureJSON fjson = new FeatureJSON();List<SimpleFeature> features = new ArrayList<>();SimpleFeatureCollection collection = new ListFeatureCollection(TYPE, features);for (String wkt : WKTS) {    LineString lineString = (LineString)reader.read(wkt);    featureBuilder.add(lineString);    featureBuilder.add("123456");    featureBuilder.add(2);    featureBuilder.add(1);    SimpleFeature feature = featureBuilder.buildFeature(null);    features.add(feature);}StringWriter writer = new StringWriter();fjson.writeFeatureCollection(collection, writer);System.out.println(writer.toString());

打印结果如下：

{“type”:”FeatureCollection”,”features”:[{“type”:”Feature”,”geometry”:{“type”:”LineString”,”coordinates”:[[255351.0429,474966.9279],[255529.2966,474272.46]]},”properties”:{“gid”:”123456”,”direction”:2,”orientation”:1},”id”:”fid-67c46b85_15e0778dd81_-8000”},{“type”:”Feature”,”geometry”:{“type”:”LineString”,”coordinates”:[[255529.2966,474272.46],[256166.0583,473979.4492]]},”properties”:{“gid”:”123456”,”direction”:2,”orientation”:1},”id”:”fid-67c46b85_15e0778dd81_-7fff”}]}

对于FeatureCollection中包含不同类型Geometry对象的情况，等遇到再研究吧。