Jackson deserialize GeoJson Point in Spring Boot

Question

I have a @Entity model that has a property of type com.vividsolutions.jts.geom.Point. When I try to render this model in a @RestController

Answer 1

As of 2020 most of the JTS libraries are outdated and no longer work. I found one fork on Maven Central that was updated recently and it worked flawlessly with jackson-core:2.10.0 and jts-core:1.16.1:

implementation 'org.n52.jackson:jackson-datatype-jts:1.2.4'

Sample usage:

    @Test
    void testJson() throws IOException {

        var objectMapper = new ObjectMapper();
        objectMapper.registerModule(new JtsModule());

        GeometryFactory gf = new GeometryFactory();
        Point point = gf.createPoint(new Coordinate(1.2345678, 2.3456789));

        String geojson = objectMapper.writeValueAsString(point);

        InputStream targetStream = new ByteArrayInputStream(geojson.getBytes());
        Point point2 = objectMapper.readValue(targetStream, Point.class);

        assertEquals(point, point2);
    }

You don't need to use any annotations on class fields or register new Spring Beans, just register the JTS module with Jackson.

Answer 2

The above workaround using JTSModule results in an internal SpringBoot error for me. I was able to solve this issue by making sure the getter methods of my Entity are returning String types.

@Entity
public class MyClassWithGeom {

    @Id
    @GeneratedValue
    private Long id;
    private Point centre;
    private Polygon boundary;

    private MyClassWithGeom() {}

    public MyClassWithGeom(String centreLat, String centreLng, Double[]... boundaryCoords) {
        String wkt = "POINT (" + centreLat + " " + centreLng + ")";
        StringBuilder builder = new StringBuilder("POLYGON (( ");

        for(int i=0;i<boundaryCoords.length;i++) {
            Double[] coord = boundaryCoords[i];
            if (i < boundaryCoords.length - 1)
                builder = builder.append(coord[0]).append(" ").append(coord[1]).append(", ");
            else
                builder = builder.append(coord[0]).append(" ").append(coord[1]).append(" ))");
        }

        try {
            this.centre = (Point) this.wktToGeometry(wkt);
            logger.info(this.centre.toString());
            this.boundary = (Polygon) this.wktToGeometry(builder.toString());
            logger.info(this.boundary.toString());
        }
        catch (ParseException pe) {
            logger.error(pe.getMessage());
            logger.error("Invalid WKT: " + wkt);
        }
    }

    public Geometry wktToGeometry(String wellKnownText) throws ParseException {
        return new WKTReader().read(wellKnownText);
    }

    public String getCentre() { return centre.toString(); }

    public String getName() { return name; }

    public String getBoundary() { return boundary.toString(); }
}

Answer 3

Maybe you should tag your geometric attribute with @JsonSerialize and @JsonDeserialize. Like this:

import com.bedatadriven.jackson.datatype.jts.serialization.GeometryDeserializer;
import com.bedatadriven.jackson.datatype.jts.serialization.GeometrySerializer;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.vividsolutions.jts.geom.Geometry;
import fr.info.groloc.entity.json.GreffeDeserializer;

import javax.persistence.Entity;

@Entity
public class Table
{
    @JsonSerialize(using = GeometrySerializer.class)
    @JsonDeserialize(contentUsing = GeometryDeserializer.class)
    private Geometry coord;
    // ...
}

If you are using Spring-Boot you only need for:

import com.bedatadriven.jackson.datatype.jts.JtsModule;
// ...
@Bean
public JtsModule jtsModule()
{
    return new JtsModule();
}

As Dave said you need to add this dependency to your pom.xml:

<dependency>
    <groupId>com.bedatadriven</groupId>
    <artifactId>jackson-datatype-jts</artifactId>
    <version>2.4</version>
</dependency>