如何基于WorldWind从内存流将Shapefile转为GeoJSON？

你已经通过内存流成功加载了Shapefile，接下来可以按照以下步骤将其转换为GeoJSON格式：

1. 初始化GeoJSON的FeatureCollection结构 #

GeoJSON的根结构是FeatureCollection，先创建基础结构并填充边界框信息：

// 初始化FeatureCollection基础结构
Map<String, Object> featureCollection = new HashMap<>();
featureCollection.put("type", "FeatureCollection");
featureCollection.put("bbox", shapefile.getBoundingRectangle());
List<Map<String, Object>> features = new ArrayList<>();
featureCollection.put("features", features);

2. 遍历ShapefileRecord转换为GeoJSON Feature #

在你已有的遍历循环中，对每个ShapefileRecord分别处理几何信息和属性：

while (shapefile.hasNext()) {
    ShapefileRecord record = shapefile.nextRecord();
    
    // 创建单个Feature对象
    Map<String, Object> feature = new HashMap<>();
    feature.put("type", "Feature");
    
    // 提取属性信息
    Map<String, Object> properties = new HashMap<>();
    ShapefileAttributes attributes = record.getAttributes();
    for (String attrName : attributes.getAttributeNames()) {
        properties.put(attrName, attributes.getValue(attrName));
    }
    feature.put("properties", properties);
    
    // 转换几何信息
    Map<String, Object> geometry = convertShapeGeometryToGeoJson(record);
    feature.put("geometry", geometry);
    
    features.add(feature);
}

3. 实现几何类型转换逻辑 #

根据WorldWind的ShapeType，将不同几何类型（点、线、面）转换为GeoJSON对应格式：

private static Map<String, Object> convertShapeGeometryToGeoJson(ShapefileRecord record) {
    Map<String, Object> geometry = new HashMap<>();
    ShapeType shapeType = record.getShapeType();
    
    switch (shapeType) {
        case POINT:
            geometry.put("type", "Point");
            Location location = record.getPointBuffer(0).getLocations().get(0);
            // GeoJSON坐标顺序为[经度, 纬度]
            geometry.put("coordinates", new double[]{location.getLongitude(), location.getLatitude()});
            break;
            
        case POLYLINE:
            geometry.put("type", "LineString");
            List<double[]> lineCoords = new ArrayList<>();
            for (Location loc : record.getPointBuffer(0).getLocations()) {
                lineCoords.add(new double[]{loc.getLongitude(), loc.getLatitude()});
            }
            geometry.put("coordinates", lineCoords);
            break;
            
        case POLYGON:
            geometry.put("type", "Polygon");
            List<List<double[]>> polygonCoords = new ArrayList<>();
            // 处理Shapefile的多环结构（外环+内环）
            for (int i = 0; i < record.getNumPointBuffers(); i++) {
                VecBuffer ringBuffer = record.getPointBuffer(i);
                List<double[]> ringCoords = new ArrayList<>();
                for (Location loc : ringBuffer.getLocations()) {
                    ringCoords.add(new double[]{loc.getLongitude(), loc.getLatitude()});
                }
                // 确保GeoJSON环闭合，若Shapefile未闭合则补全起点坐标
                if (!ringCoords.isEmpty()) {
                    double[] first = ringCoords.get(0);
                    double[] last = ringCoords.get(ringCoords.size()-1);
                    if (first[0] != last[0] || first[1] != last[1]) {
                        ringCoords.add(first);
                    }
                }
                polygonCoords.add(ringCoords);
            }
            geometry.put("coordinates", polygonCoords);
            break;
            
        // 按需扩展MULTIPOINT、MULTIPOLYGON等其他类型
        default:
            geometry.put("type", "GeometryCollection");
            geometry.put("geometries", Collections.emptyList());
            break;
    }
    
    return geometry;
}

4. 序列化GeoJSON为字符串 #

用JSON库（如Jackson）将FeatureCollection转为JSON字符串：

ObjectMapper mapper = new ObjectMapper();
String geoJsonString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(featureCollection);
// 输出或使用转换后的GeoJSON字符串
log.debug("转换完成的GeoJSON: {}", geoJsonString);

注意事项 #

• GeoJSON坐标顺序为**[经度, 纬度]**，需注意与WorldWind Location（纬度优先）的顺序差异。
• Shapefile的Polygon可能包含内环（表示洞），转换时需保留环的层级结构。
• 可根据需求扩展更多ShapeType的转换逻辑。

内容的提问来源于stack exchange，提问作者George