PostGis 数据库中有一个 CircularString (EWKT) 几何图形。它是通过以下 SQL 插入的:
INSERT INTO objectwithgeometries (id,geometry,remarks) VALUES ( 41, ST_SetSRID( ST_GeomFromEWKT( 'CIRCULARSTRING(29.8925 41.36667,29.628611 41.015000,29.27528 41.31667)'), 4326), 'remark-3');
结果是:
尝试 1:尝试使用 postgisRepo.findAll();
读取对象时...错误是:
org.geolatte.geom.codec.WkbDecodeException:不支持的 WKB 类型代码: 8
在查看 WktDialect 类时,我只看到标准的 7 个 WKB 类型。不是 CurularString。
尝试 2:使用 JDBC 读取:
List<Map<String, Object>> objects = jdbcTemplate.queryForList( String.format( "select id,geometry,remarks from objectwithgeometries where id = %d", id));
objects.forEach( r -> {
WKBReader wkbReader = new WKBReader();
PGobject geometryObject = (PGobject) r.get( "geometry");
byte[] geom = WKBReader.hexToBytes( geometryObject.getValue() );
try {
log.info( "Geometry: {}", wkbReader.read(geom));
} catch (ParseException e) {
throw new RuntimeException(e);
}
});
这也会抛出异常:org.locationtech.jts.io.ParseException: Unknown WKB type 8
Spring Boot 2 或 3(与 Hibernate 5 或 6)没有区别。
Try-3:使用 PGobject、PGGeometry 等。这些对象可通过 maven 依赖项获得:
<dependency>
<groupId>net.postgis</groupId>
<artifactId>postgis-jdbc</artifactId>
<version>2023.1.0</version>
</dependency>
这样做的问题是,它在 jdbcTemplate.queryForList() 期间给出错误(未知几何类型:8);-(。
Try-4:通过不同方法的独立示例。效果是一样的:未知几何类型:8。
Class.forName("org.postgresql.Driver");
String url = "jdbc:postgresql://localhost:5433/postgis";
conn = DriverManager.getConnection(url, "xyz", "abc");
((org.postgresql.PGConnection)conn).addDataType("geometry",
(Class<? extends PGobject>) Class.forName("net.postgis.jdbc.PGgeometry"));
Statement s = conn.createStatement();
ResultSet r = s.executeQuery("select id,geometry,remarks from objectwithgeometries where id = 43");
while( r.next() ) {
PGgeometry geom = (PGgeometry)r.getObject(2);
int id = r.getInt(1);
System.out.println("Row " + id + ":");
System.out.println(geom.toString());
}
s.close();
conn.close();
如何在 Spring JPA 中读取这个(EWKT)对象?
我使用 org.hibernate.spatial.dialect.postgis.PostgisDialect 来访问几何图形。
此外,请注意,通过 Spring JPA 执行上述“插入”语句通常会导致连接超时。
终于找到解决办法了。欢迎有更优雅的解决方案。
import org.geotools.geometry.jts.CircularString;
import org.geotools.geometry.jts.CurvedGeometryFactory;
import org.geotools.geometry.jts.JTSFactoryFinder;
import org.geotools.geometry.jts.WKTReader2;
import org.locationtech.jts.geom.GeometryFactory;
import org.postgresql.util.PGobject;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class PostgisReaderStandaloneAsText {
public static void main(String[] args) {
java.sql.Connection conn;
try {
Class.forName("org.postgresql.Driver");
String url = "jdbc:postgresql://localhost:5433/postgis";
conn = DriverManager.getConnection(url, "postgis", "postgis");
Statement s = conn.createStatement();
ResultSet r = s.executeQuery("select id,ST_AsText(geometry),remarks from objectwithgeometries where id = 43");
while( r.next() ) {
String geom = (String) r.getObject(2);
int id = r.getInt(1);
System.out.println("Row " + id + " = " + geom.toString());
GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();
CurvedGeometryFactory curvedfactory = new CurvedGeometryFactory(Double.MAX_VALUE);
WKTReader2 reader = new WKTReader2(curvedfactory);
CircularString arc = (CircularString) reader.read(geom);
System.out.println( "Arc = " + arc);
}
s.close();
conn.close();
}
catch( Exception e ) {
e.printStackTrace();
}
}
}
结果是:
Row 43 = CIRCULARSTRING(29.8925 41.36667,29.628611 41.015,29.27528 41.31667) Arc = CIRCULARSTRING (29.8925 41.36667, 29.628611 41.015, 29.27528 41.31667)
因为 JTS 无法处理曲线,所以您可以制作一个具有致密(中间 0 个点)的 LineString。