Hibernate Spatial with PostGIS's Geography Typ

问题:

I just added a column of type Geography to a Postgres database that is accessed by an application using hibernate and hibernate spatial. Whenever I access that column with hibernate I get an error saying "Can't convert object of type org.postgresql.util.PGobject". I was using an older version of hibernate spatial but it seems that even the newest version does not support the Geography datatype. Is this really the case or did I just miss something. Is there a way I can work around this limitation?

回答1:

I had a similar issue using Glassfish 3.1.2 + Toplink. And I solved it implementing a SessionCustomizer. I believe that you can use the same aproach for Geograph datatypes.

PostGISJPACustomizer.java

public class PostGISJPACustomizer implements SessionCustomizer {

    @Override
    public void customize(Session s) throws Exception {
        RelationalDescriptor desc01 = (RelationalDescriptor) s.getDescriptor(SentenceGPS.class);
        DirectToFieldMapping mapping01 = (DirectToFieldMapping) desc01.getMappingForAttributeName("geom");
        mapping01.setConverter(null);

        RelationalDescriptor desc02 = (RelationalDescriptor) s.getDescriptor(SentenceLine.class);
        DirectToFieldMapping mapping02 = (DirectToFieldMapping) desc02.getMappingForAttributeName("geom");
        mapping02.setConverter(null);

        RelationalDescriptor desc03 = (RelationalDescriptor) s.getDescriptor(SentencePolygon.class);
        DirectToFieldMapping mapping03 = (DirectToFieldMapping) desc03.getMappingForAttributeName("geom");
        mapping03.setConverter(null);
    }
}

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
    <persistence-unit name="onet-ejbPU" transaction-type="JTA">
    <jta-data-source>jdbc/onet</jta-data-source>
       <exclude-unlisted-classes>false</exclude-unlisted-classes>
       <properties>
           <property name="eclipselink.session.customizer" value="com.util.PostGISJPACustomizer"/>
       </properties>
    </persistence-unit>
</persistence>

SentenceGPS.java (partial)

@Entity
public class SentenceGPS implements Serializable {

    @Column
    private PGgeometry geom;

    public void setGeom(LineString geom) {
        this.geom = GeoUtils.getPGeo(geom);
    }

    public LineString getGeom() {
        return (LineString) GeoUtils.getJTS(geom);
    }
}

GeoUtils.java

public class GeoUtils {

    public static PGgeometry getPGeo(Geometry g) throws SQLException {
        String PGgeometryStr = "SRID=" + g.getSRID() + ";" + g.toString();
        PGgeometry pg = new PGgeometry(PGgeometry.geomFromString(PGgeometryStr));
        return pg;
    }

    // This function needs improvements due peformance issues
    public static Geometry getJTS(PGgeometry g) throws ParseException, SQLException {
        WKTReader reader = new WKTReader(new GeometryFactory(new PrecisionModel(PrecisionModel.FLOATING), g.getGeometry().getSrid()));
        String geometryString = g.getGeometry().toString();

        Geometry geom;
        if (geometryString.indexOf(';') != -1) {
            String[] temp = PGgeometry.splitSRID(geometryString);
            int srid = Integer.parseInt(temp[0].substring(5));
            geom = (Geometry) reader.read(temp[1]);
            geom.setSRID(srid);
        } else {
            geom = (Geometry) reader.read(geometryString);
        }
        return geom;
    }
}