java kml 转geojson

从Java KML转GeoJSON的方法

在地理信息系统领域，KML（Keyhole Markup Language）和GeoJSON是两种常见的数据格式，用于描述地理空间信息。KML是由Google创建的一种XML形式的标记语言，用于表示地理空间数据，而GeoJSON则是一种基于JSON的开放标准格式，用于表示地理空间数据。

本文将介绍如何使用Java将KML格式的地理空间数据转换为GeoJSON格式的数据。我们将使用Java中的一些开源库来实现这个转换过程，包括JTS Topology Suite和GeoTools。

步骤流程

下面是从KML转换为GeoJSON的基本步骤流程：

flowchart TD
    A(读取KML文件) --> B(解析KML数据)
    B --> C(转换成JTS对象)
    C --> D(将JTS对象转换为GeoJSON)
    D --> E(写入GeoJSON文件)

代码示例

1. 读取KML文件

import java.io.File;
import java.io.IOException;
import org.geotools.data.DataUtilities;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.data.simple.SimpleShapeFileIn;
import org.geotools.data.simple.SimpleShapeFileIn.ShapeType;
import org.opengis.feature.simple.SimpleFeature;

public class KmlReader {

    public SimpleFeatureCollection readKmlFile(File kmlFile) throws IOException {
        SimpleShapeFileIn reader = new SimpleShapeFileIn(kmlFile);
        SimpleFeatureSource featureSource = reader.getFeatureSource();
        SimpleFeatureCollection featureCollection = featureSource.getFeatures();
        reader.dispose();
        return featureCollection;
    }
}

2. 解析KML数据并转换成JTS对象

import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.io.WKTReader;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;

public class KmlParser {

    public Geometry parseKmlFeature(SimpleFeature feature) {
        SimpleFeatureType featureType = feature.getFeatureType();
        Geometry geometry = null;
        if (featureType.getGeometryDescriptor() != null) {
            String wkt = (String) feature.getAttribute(featureType.getGeometryDescriptor().getLocalName());
            WKTReader wktReader = new WKTReader();
            try {
                geometry = wktReader.read(wkt);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return geometry;
    }
}

3. 将JTS对象转换为GeoJSON

import org.geojson.Feature;
import org.geojson.FeatureCollection;
import org.geojson.Geometry;
import org.geojson.jts.Converter;
import org.locationtech.jts.geom.Geometry;
import org.opengis.feature.simple.SimpleFeature;

public class GeoJsonConverter {

    public FeatureCollection convertToGeoJson(SimpleFeatureCollection featureCollection) {
        FeatureCollection geoJsonCollection = new FeatureCollection();
        Converter converter = new Converter();
        for (SimpleFeature feature : featureCollection) {
            Geometry geometry = (Geometry) feature.getDefaultGeometry();
            Geometry geoJsonGeometry = converter.fromJts(geometry);
            Feature geoJsonFeature = new Feature();
            geoJsonFeature.setGeometry((Geometry) geoJsonGeometry);
            geoJsonCollection.add(geoJsonFeature);
        }
        return geoJsonCollection;
    }
}

4. 写入GeoJSON文件

import java.io.File;
import java.io.FileWriter;
import org.geojson.FeatureCollection;

public class GeoJsonWriter {

    public void writeGeoJsonFile(File geoJsonFile, FeatureCollection featureCollection) {
        try (FileWriter writer = new FileWriter(geoJsonFile)) {
            writer.write(featureCollection.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

完整代码示例

import org.geotools.data.simple.SimpleFeatureCollection;
import java.io.File;
import java.io.IOException;

public class KmlToGeoJsonConverter {

    public static void main(String[] args) {
        File kmlFile = new File("input.kml");
        File geoJsonFile = new File("output.geojson");

        try {
            // 读取KML文件
            KmlReader kmlReader = new KmlReader();
            SimpleFeatureCollection featureCollection = kmlReader.readKmlFile(kmlFile);

            // 解析KML数据并转换成JTS对象
            KmlParser kmlParser = new KmlParser();
            GeoJsonConverter geoJsonConverter = new GeoJsonConverter();
            FeatureCollection geoJsonCollection = geoJsonConverter.convertToGeoJson(featureCollection);

            // 将JTS对象转换为GeoJSON并写入文件
            GeoJsonWriter geoJsonWriter = new GeoJson