1.業務需求
查詢帶有經緯度數據的list列表，將其轉為geojson格式給前端。
2.GeoJson格式說明
GeoJSON是一種對各種地理數據結構進行編碼的格式，基于Javascript對象表示法(JavaScript Object Notation, 簡稱JSON)的地理空間信息數據交換格式。GeoJSON對象可以表示幾何、特征或者特征集合。GeoJSON支持下面這幾種幾何類型：點、線、面、多點、多線、多面和幾何集合。GeoJSON里的特征包含一個幾何對象和其他屬性，特征集合表示一系列特征。
3.JAVA代碼實現：
public Map getSectionStringGeojson(DataBaseSection dataBaseSection) {Map map = new HashMap();//查詢斷面數據List<DataBaseSection> dataBaseSectionList = dataBaseSectionMapper.selectDataBaseSectionListNoGeom(dataBaseSection);if(dataBaseSectionList == null || dataBaseSectionList.size() == 0) {return map;}//使用stream方法，獲取dataBaseSectionList中lgtd的最大值和最小值BigDecimal maxLgtd = dataBaseSectionList.stream().map(DataBaseSection::getLgtd).max(BigDecimal::compareTo).get();BigDecimal minLgtd = dataBaseSectionList.stream().map(DataBaseSection::getLgtd).min(BigDecimal::compareTo).get();BigDecimal maxLttd = dataBaseSectionList.stream().map(DataBaseSection::getLttd).max(BigDecimal::compareTo).get();BigDecimal minLttd = dataBaseSectionList.stream().map(DataBaseSection::getLttd).min(BigDecimal::compareTo).get();map.put("maxLgtd", maxLgtd);map.put("minLgtd", minLgtd);map.put("maxLttd", maxLttd);map.put("minLttd", minLttd);//創建一個空的 SimpleFeatureTypeBuilder 對象，并添加屬性字段：SimpleFeatureTypeBuilder builder = new SimpleFeatureTypeBuilder();builder.setName("Section");builder.add("geometry", Point.class);builder.add("bscd", String.class);builder.add("bscnm", String.class);builder.add("sttp", String.class);builder.add("fcd", String.class);builder.add("ocd", String.class);//使用 SimpleFeatureBuilder 創建一個 SimpleFeatureType 對象：SimpleFeatureType featureType = builder.buildFeatureType();SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(featureType);DefaultFeatureCollection featureCollection = new DefaultFeatureCollection();//遍歷查詢結果集，將每一行數據轉換為一個 SimpleFeature 對象，并將其添加到 SimpleFeatureCollection 中：for(int i = 0; i < dataBaseSectionList.size(); i++) {DataBaseSection obj = dataBaseSectionList.get(i);//存儲數據double x = obj.getLgtd().doubleValue();double y = obj.getLttd().doubleValue();// 創建一個 Point 對象GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();Coordinate coordinate = new Coordinate(x, y);Point point = geometryFactory.createPoint(coordinate);// 將坐標和屬性數據設置到 SimpleFeature 對象中featureBuilder.add(point);featureBuilder.add(obj.getBscd());featureBuilder.add(obj.getBscnm());featureBuilder.add(obj.getSttp());featureBuilder.add(obj.getFcd());featureBuilder.add(obj.getOcd());SimpleFeature feature = featureBuilder.buildFeature(null);// 將 SimpleFeature 對象添加到 SimpleFeatureCollection 中featureCollection.add(feature);}//使用 FeatureJSON 將 SimpleFeatureCollection 轉換為 GeoJSON 字符串：String geojson = "";try {if(featureCollection != null && featureCollection.size() > 0){geojson = new FeatureJSON().toString(featureCollection);}}catch (IOException e){System.out.println("基礎斷面geojson文件保存異常！");}map.put("geojson", geojson);return map;}
