public JTSLineStringExpression<?> exteriorRing() {
        if (exteriorRing == null) {
            exteriorRing = JTSGeometryExpressions.lineStringOperation(SpatialOps.EXTERIOR_RING, mixin);
        }
        return exteriorRing;
    }
Returns the exterior ring of this Polygon.

@return exterior ring
querydsl-spatial/src/main/java/com/querydsl/spatial/jts/JTSPolygonExpression.java