geom怎么转换为WKT格式数据

在PostGIS中，可以使用ST_AsText函数将geom类型的几何对象转换为WKT格式的文本。例如，假设我们有一个名为"mytable"的表，其中包含了一个名为"geom"的几何字段，我们可以使用以下的SQL语句将其转换为WKT格式的文本：

SELECT ST_AsText(geom) FROM mytable;

执行该语句后，会返回一个包含了所有几何对象WKT格式文本的结果集。这些文本可以直接复制到文本文件或其他应用程序中进行使用。

相关问题

使用python将wkb转换为wkt

可以使用Python的GeoPandas库来将wkb转换为wkt。以下是一个简单的示例代码：

import geopandas as gpd
from shapely import wkb

# 读取wkb数据
with open('data.wkb', 'rb') as f:
    wkb_data = f.read()

# 将wkb转换为shapely几何对象
geom = wkb.loads(wkb_data)

# 将shapely几何对象转换为GeoDataFrame
gdf = gpd.GeoDataFrame(geometry=[geom])

# 将GeoDataFrame中的几何对象转换为wkt格式
gdf['wkt'] = gdf['geometry'].apply(lambda x: x.wkt)

# 打印wkt字符串
print(gdf.iloc[0]['wkt'])

需要注意的是，如果wkb数据包含多个几何对象，那么需要在转换为GeoDataFrame时指定几何列的名称。例如：

gdf = gpd.GeoDataFrame(geometry=gpd.GeoSeries.from_wkb(wkb_data), geometry='geom')

其中，'geom'是几何列的名称，可以根据实际情况进行修改。

postGis有这样一张表test：字段id，空间数据geom，time字段。现在需要前端输入时间参数，后端按这个参数查询数据库数据，将查询到的数据导出为一份shp文件。现在我使用语句 select id，ST_AsText(geom) as wkt,time from test where time='2023 04-25 00:00'查出需要的结果，请给出一份完整的代码示例，使用springboot框架，给出包含实体类、mapper层、service、serviceImpl、controller的所有代码 可以使用geotools或gdal

以下是使用 GeoTools 的完整代码示例，包含实体类、mapper 层、service、serviceImpl、controller 的所有代码。

1. 实体类

import org.locationtech.jts.geom.Geometry;

public class TestEntity {
    private Long id;
    private Geometry geom;
    private String time;

    // getter 和 setter 略
}

2. Mapper 层

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.locationtech.jts.geom.Geometry;

import java.util.List;

@Mapper
public interface TestMapper {
    @Select("SELECT id, geom, time FROM test WHERE time = #{time}")
    List<TestEntity> findByTime(@Param("time") String time);

    @Select("SELECT ST_AsText(geom) FROM test WHERE id = #{id}")
    String findWktById(@Param("id") Long id);
}

3. Service

import java.util.List;

public interface TestService {
    List<TestEntity> findByTime(String time);

    byte[] exportToShp(List<TestEntity> entities);
}

4. ServiceImpl

import org.geotools.data.DefaultTransaction;
import org.geotools.data.Transaction;
import org.geotools.data.shapefile.ShapefileDataStore;
import org.geotools.data.shapefile.ShapefileDataStoreFactory;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.data.simple.SimpleFeatureIterator;
import org.geotools.feature.simple.SimpleFeatureBuilder;
import org.geotools.feature.simple.SimpleFeatureTypeBuilder;
import org.geotools.geometry.jts.JTSFactoryFinder;
import org.locationtech.jts.geom.Geometry;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.sql.DataSource;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Service
public class TestServiceImpl implements TestService {
    @Autowired
    private TestMapper testMapper;

    @Autowired
    private DataSource dataSource;

    @Override
    public List<TestEntity> findByTime(String time) {
        return testMapper.findByTime(time);
    }

    @Override
    @Transactional(readOnly = true)
    public byte[] exportToShp(List<TestEntity> entities) {
        ShapefileDataStoreFactory dataStoreFactory = new ShapefileDataStoreFactory();

        Map<String, Object> params = new HashMap<>();
        params.put("url", getTempFileUrl());
        params.put("create spatial index", Boolean.TRUE);

        ShapefileDataStore dataStore;
        try {
            dataStore = (ShapefileDataStore) dataStoreFactory.createNewDataStore(params);
        } catch (IOException e) {
            throw new RuntimeException("创建 ShapefileDataStore 失败", e);
        }

        SimpleFeatureTypeBuilder typeBuilder = new SimpleFeatureTypeBuilder();
        typeBuilder.setName("TestEntity");
        typeBuilder.setCRS(org.geotools.referencing.crs.DefaultGeographicCRS.WGS84);
        typeBuilder.add("geom", Geometry.class);
        typeBuilder.add("id", Long.class);
        typeBuilder.add("time", String.class);
        SimpleFeatureType featureType = typeBuilder.buildFeatureType();

        try {
            dataStore.createSchema(featureType);
        } catch (IOException e) {
            throw new RuntimeException("创建 Schema 失败", e);
        }

        Transaction transaction = new DefaultTransaction("create");

        String typeName = dataStore.getTypeNames()[0];
        SimpleFeatureSource featureSource;
        try {
            featureSource = dataStore.getFeatureSource(typeName);
        } catch (IOException e) {
            throw new RuntimeException("获取 FeatureSource 失败", e);
        }

        List<SimpleFeature> features = new ArrayList<>();
        SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(featureType);
        GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();

        for (TestEntity entity : entities) {
            Geometry geometry = entity.getGeom();
            Long id = entity.getId();
            String time = entity.getTime();
            SimpleFeature feature = featureBuilder.buildFeature(null);
            feature.setDefaultGeometry(geometry);
            feature.setAttribute("id", id);
            feature.setAttribute("time", time);
            features.add(feature);
        }

        try {
            SimpleFeatureCollection featureCollection = new ListFeatureCollection(featureType, features);
            featureSource.addFeatures(featureCollection);
            transaction.commit();
        } catch (IOException e) {
            throw new RuntimeException("添加 Feature 失败", e);
        } finally {
            try {
                transaction.close();
            } catch (IOException e) {
                throw new RuntimeException("关闭 Transaction 失败", e);
            }
        }

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        try {
            org.geotools.data.DataUtilities.encodeFeatureCollection(featureSource.getFeatures(), outputStream);
        } catch (IOException e) {
            throw new RuntimeException("编码 FeatureCollection 失败", e);
        }

        return outputStream.toByteArray();
    }

    private String getTempFileUrl() {
        try {
            return "file://" + java.nio.file.Files.createTempFile("temp", ".shp").toAbsolutePath();
        } catch (IOException e) {
            throw new RuntimeException("创建临时文件失败", e);
        }
    }
}

5. Controller

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.nio.charset.StandardCharsets;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.List;

@RestController
public class TestController {
    @Autowired
    private TestService testService;

    @GetMapping("/export")
    public ResponseEntity<byte[]> export(@RequestParam String time) {
        List<TestEntity> entities = testService.findByTime(time);
        byte[] shpBytes = testService.exportToShp(entities);

        String filename = "test_" + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyyMMddHHmmss")) + ".zip";

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        headers.setContentDispositionFormData("attachment", filename, StandardCharsets.UTF_8);

        return ResponseEntity.ok().headers(headers).body(shpBytes);
    }
}

希望这份代码对你有所帮助！