Spring Boot JPA with Hibernate 空间自参考导致循环

Question

I am currently writing a service where I can store a geospatial point with some data. I have a "dataPoint" class that looks like this:

@Entity
@Table(name = "datapoint")
public class DataPoint {
    @Id
    int dataPoint_id;

    @Column(name = "body")
    String body;

    @Column(name = "location", columnDefinition = "Geometry")
    PGgeometry location;

    @Column(name = "deleted")
    boolean deleted;

    //Getters and Setters...

I am trying to use Spring Boot to simply add a point with some information to a PostGIS database via an API path. I have built a controller that looks like this:

@RestController
@RequestMapping(value = "/dataPoint")
public class DataPointController {

    @Autowired
    private DataPointService myPointService;

    @RequestMapping(value = "/add/{body}/{latitude}/{longitude}/")
    public DataPoint addDataPoint(@PathVariable String body, @PathVariable double latitude, @PathVariable double longitude){
        DataPoint myPoint = new DataPoint();
        myPoint.setBody(body);
        PGgeometry geometry = new PGgeometry();
        try {
            geometry.setValue("POINT("+longitude +" " + latitude+")");
            geometry.setType("POINT");
            // Debugging Stuff
            System.out.println("GEOMETRY VALUE LOOK: {{{{ " + geometry.getValue() + "   " + geometry.getType());
        } catch (SQLException e) {
            e.printStackTrace();
        }
        myPoint.setLocation(geometry);
        myPointService.saveDataPoint(myPoint);
        return myPoint;
    }

Which is in turn linked to a DataPointService which just acts as a middle man between the controller where saveDataPoint() looks like this:

public void saveDataPoint(DataPoint myPoint) {
    dataPointRepository.save(myPoint);
}

and the DataPointRepository , which looks like this:

@Repository
public interface DataPointRepository extends JpaRepository<DataPoint, Integer> {
}

However, when I visit my add link, I get this error:

Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Direct self-reference leading to cycle (through reference chain: com.testing.model.DataPoint["location"]->org.postgis.PGgeometry["geometry"]->org.postgis.Point["firstPoint"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Direct self-reference leading to cycle (through reference chain: com.testing.model.DataPoint["location"]->org.postgis.PGgeometry["geometry"]->org.postgis.Point["firstPoint"])

I have seen the @JsonBackReference and its dual used in some examples, however, that has been used in situations where entities are being linked back and forth, which I do not see happening here, in fact, the error does not even seem to be cyclic, so what is happening here?

Answer 1

I ran into the same issue. It's cyclic because Point has a field firstPoint that reference to Point again. I was able to resolve the problem by installing this postgis-geojson: https://jitpack.io/p/stephenbrough/postgis-geojson