GeometryConverter.java

package org.mongodb.morphia.geo;

import com.mongodb.DBObject;
import org.mongodb.morphia.converters.SimpleValueConverter;
import org.mongodb.morphia.converters.TypeConverter;
import org.mongodb.morphia.mapping.MappedField;

/**
 * A Morphia TypeConverter that knows how to turn things that are labelled with the Geometry interface into the correct concrete class,
 * based on the GeoJSON type.
 * <p/>
 * Only implements the decode method as the concrete classes can encode themselves without needing a converter. It's when they come out of
 * the database that there's not enough information for Morphia to automatically create Geometry instances.
 */
public class GeometryConverter extends TypeConverter implements SimpleValueConverter {
    /**
     * Sets up this converter to work with things that implement the Geometry interface
     */
    public GeometryConverter() {
        super(Geometry.class);
    }

    @Override
    public Object decode(final Class<?> targetClass, final Object fromDBObject, final MappedField optionalExtraInfo) {
        DBObject dbObject = (DBObject) fromDBObject;
        String type = (String) dbObject.get("type");
        return getMapper().getConverters().decode(GeoJsonType.fromString(type).getTypeClass(), fromDBObject, optionalExtraInfo);
    }
}