Итак, я пытался отобразить GeoJSON в C # DataContracts, чтобы мы могли легко поддерживать возвращение GeoJSON в нашем WCF / REST-apis.Чем больше я работаю с DataContracts и сериализацией, тем больше у меня возникает ощущение, что это черный ящик магии, который я не могу понять.
Как бы то ни было, я дошел до:
GeoJSON.cs:
namespace GeoJSON {
[DataContract]
[KnownType(typeof (Point))]
[KnownType(typeof (MultiPoint))]
[KnownType(typeof (LineString))]
[KnownType(typeof (MultiLineString))]
[KnownType(typeof (Polygon))]
[KnownType(typeof (MultiPolygon))]
[KnownType(typeof (Feature))]
[KnownType(typeof (FeatureCollection))]
[KnownType(typeof (Geometry))]
[KnownType(typeof(GeometryCollection))]
public abstract class GeoJson {
// This is because WCF services can't read the DataContracts KnownType's above
// so you need to break DRY and repeat yourself here and add this class
// to a ServiceKnownType-attribute to every service method returning GeoJSON
// Like this:
// [ServiceKnownType("Types", typeof(GeoJson.KnownTypes))]
public static class KnownTypes {
public static Type[] Types(ICustomAttributeProvider provider) {
return new[] {
typeof (Point),
typeof (MultiPoint),
typeof (LineString),
typeof (MultiLineString),
typeof (Polygon),
typeof (MultiPolygon),
typeof (Feature),
typeof (FeatureCollection),
typeof (Geometry),
typeof (GeometryCollection)
};
}
}
}
#region Feature
// The idea here (and elsewhere) is that if i let the type field be enums the
// deserializer might use that information to chose the right class.
// Is this just crack?
[DataContract]
public enum FeatureType {
[EnumMember] Feature
}
public class Feature : GeoJson {
public Feature() {
Type = FeatureType.Feature;
Properties = new Dictionary<string, string>();
}
public Feature(Geometry geometry) {
Type = FeatureType.Feature;
Properties = new Dictionary<string, string>();
Geometry = geometry;
}
[DataMember(Name = "type")]
public FeatureType Type { get; set; }
[DataMember(Name = "id")]
public string Id { get; set; }
[DataMember(IsRequired = true, Name = "geometry")]
public Geometry Geometry { get; set; }
// TODO: Make this support proper JSON-trees
[DataMember(IsRequired = true, Name = "properties")]
public IDictionary<string, string> Properties { get; set; }
}
#endregion Feature
#region FeatureCollection
[DataContract]
public enum FeatureCollectionType {
[EnumMember]
FeatureCollection
}
[DataContract(Name = "FeatureCollection")]
public class FeatureCollection : GeoJson {
public FeatureCollection() {
Type = FeatureCollectionType.FeatureCollection;
Features = new Feature[0];
}
public FeatureCollection(params Feature[] features) {
Type = FeatureCollectionType.FeatureCollection;
Features = features ?? new Feature[0];
}
[DataMember(Name = "type")]
private FeatureCollectionType Type { get; set; }
[DataMember(Name = "features", IsRequired = true)]
private Feature[] Features { get; set; }
}
#endregion FeatureCollection
#region GeometryCollection
[DataContract]
public enum GeometryCollectionType {
[EnumMember] GeometryCollection
}
[DataContract(Name = "GeometryCollection")]
public class GeometryCollection : GeoJson {
public GeometryCollection() {
Type = GeometryCollectionType.GeometryCollection;
Geometries = new Geometry[0];
}
public GeometryCollection(params Geometry[] geometries) {
Type = GeometryCollectionType.GeometryCollection;
Geometries = geometries ?? new Geometry[0];
}
[DataMember(Name = "type")]
private GeometryCollectionType Type { get; set; }
[DataMember(Name = "geometries", IsRequired = true)]
private Geometry[] Geometries { get; set; }
}
#endregion GeometryCollection
#region Geometry
/* TODO:
* - More constructors
* - Enforce some more invariants.
*/
[DataContract]
[KnownType(typeof(Point))]
[KnownType(typeof(MultiPoint))]
[KnownType(typeof(LineString))]
[KnownType(typeof(MultiLineString))]
[KnownType(typeof(Polygon))]
[KnownType(typeof(MultiPolygon))]
public abstract class Geometry : GeoJson { }
[DataContract]
public enum PointType {
[EnumMember(Value="Point")] Point
}
[DataContract]
public class Point : Geometry {
public Point() {
Type = PointType.Point;
}
[DataMember(Name = "type", Order = 0)]
public PointType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[] Coordinates { get; set; }
}
[DataContract]
public enum MultiPointType {
[EnumMember(Value = "MultiPoint")] MultiPoint
}
[DataContract]
public class MultiPoint : Geometry {
public MultiPoint() {
Type = MultiPointType.MultiPoint;
}
[DataMember(Name = "type", Order = 0)]
public MultiPointType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[][] Coordinates { get; set; }
}
[DataContract]
public enum LineStringType {
[EnumMember] LineString
}
[DataContract]
public class LineString : Geometry {
public LineString() {
Type = LineStringType.LineString;
}
[DataMember(Name = "type", Order = 0)]
public LineStringType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[] Coordinates { get; set; }
}
[DataContract]
public enum MultiLineStringType {
[EnumMember] MultiLineString
}
[DataContract]
public class MultiLineString : Geometry {
public MultiLineString() {
Type = MultiLineStringType.MultiLineString;
}
[DataMember(Name = "type", Order = 0)]
public MultiLineStringType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[][] Coordinates { get; set; }
}
[DataContract]
public enum PolygonType {
[EnumMember] Polygon
}
[DataContract]
public class Polygon : Geometry {
public Polygon() {
Type = PolygonType.Polygon;
}
[DataMember(Name = "type", Order = 0)]
public PolygonType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[][] Coordinates { get; set; }
}
[DataContract]
public enum MultiPolygonType {
[EnumMember] MultiPolygon
}
[DataContract]
public class MultiPolygon : Geometry {
public MultiPolygon() {
Type = MultiPolygonType.MultiPolygon;
}
[DataMember(Name = "type", Order = 0)]
public MultiPolygonType Type { get; set; }
[DataMember(Name = "coordinates", Order = 1)]
public double[][][] Coordinates { get; set; }
}
#endregion Geometry
}
Program.cs:
namespace Test {
internal class Program {
private static void Main(string[] args) {
var linestring = new LineString {
Coordinates = new[] {12.0, 57.1, 13, 14}
};
var point = new Point {
Coordinates = new[] { 12.0, 57.1 }
};
var geometryCollection = new GeometryCollection(point, linestring);
var feature = new Feature(linestring);
var featureCollection = new FeatureCollection(
feature,
new Feature(point)
);
try {
WriteObject("LineString", linestring);
WriteObject("Point", point);
WriteObject("GeometryCollection",geometryCollection);
WriteObject("Feature", feature);
WriteObject("FeatureCollection", featureCollection);
}
catch (Exception ex) {
Console.WriteLine("An exception occured: " + ex.Message);
}
Console.ReadKey();
}
public static void WriteObject(string label, GeoJson json) {
var stream = new MemoryStream();
var ser = new DataContractJsonSerializer(json.GetType());
ser.WriteObject(stream, json);
stream.Position = 0;
var sr = new StreamReader(stream);
Console.Write("\n" + label + ":\n\t");
Console.WriteLine(sr.ReadToEnd());
}
}
}
Вывод программы:
LineString:
{"type":0,"coordinates":[12,57.1,13,14]}
Point:
{"type":0,"coordinates":[12,57.1]}
GeometryCollection:
{"geometries":[{"__type":"Point:#GeoJSON","type":0,"coordinates":[12,57.1]},{"__type":"LineString:#GeoJSON","type":0,"coordinates":[12,57.1,13,14]}],"type":0}
Feature:
{"geometry":{"__type":"LineString:#GeoJSON","type":0,"coordinates":[12,57.1,13,14]},"id":null,"properties":[],"type":0}
FeatureCollection:
{"features":[{"geometry":{"__type":"LineString:#GeoJSON","type":0,"coordinates":[12,57.1,13,14]},"id":null,"properties":[],"type":0},{"geometry":{"__type":"Point:#GeoJSON","type":0,"coordinates":[12,57.1]},"id":null,"properties":[], "type":0}],"type":0}
Проблемы
- Я получаю эти __type-теги, разбросанные вокруг
- Поля типов сериализуются в «0» вместо их фактических имен.
Я получаю эти проблемы также при использовании их в WCFСервисы.Есть идеи?Любой намек на то, будут ли у меня проблемы с десериализацией этого или эта идея вообще разумна?