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SubTypes.cs
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using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Collections;
using System.Reflection;
using Newtonsoft.Json.Linq;
namespace ExpressBase.Objects.ObjectBase
{
// Copyright 2017 Emmanuel Counasse
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at [apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
public class JsonSubtypes : JsonConverter
{
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = true)]
public class KnownSubTypeAttribute : Attribute
{
public Type SubType { get; private set; }
public object AssociatedValue { get; private set; }
public KnownSubTypeAttribute(Type subType, object associatedValue)
{
SubType = subType;
AssociatedValue = associatedValue;
}
}
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = true)]
public class KnownSubTypeWithPropertyAttribute : Attribute
{
public Type SubType { get; private set; }
public string PropertyName { get; private set; }
public KnownSubTypeWithPropertyAttribute(Type subType, string propertyName)
{
SubType = subType;
PropertyName = propertyName;
}
}
private readonly string _typeMappingPropertyName;
private bool _isInsideRead;
private JsonReader _reader;
public override bool CanRead
{
get
{
if (!_isInsideRead)
return true;
return !string.IsNullOrEmpty(_reader.Path);
}
}
public sealed override bool CanWrite
{
get { return false; }
}
public JsonSubtypes()
{
}
public JsonSubtypes(string typeMappingPropertyName)
{
_typeMappingPropertyName = typeMappingPropertyName;
}
public override bool CanConvert(Type objectType)
{
return false;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue,
JsonSerializer serializer)
{
return ReadJson(reader, objectType, serializer);
}
private object ReadJson(JsonReader reader, Type objectType, JsonSerializer serializer)
{
while (reader.TokenType == JsonToken.Comment)
reader.Read();
object value;
switch (reader.TokenType)
{
case JsonToken.Null:
value = null;
break;
case JsonToken.StartObject:
value = ReadObject(reader, objectType, serializer);
break;
case JsonToken.StartArray:
value = ReadArray(reader, objectType, serializer);
break;
default:
var lineNumber = 0;
var linePosition = 0;
var lineInfo = reader as IJsonLineInfo;
if (lineInfo != null && lineInfo.HasLineInfo())
{
lineNumber = lineInfo.LineNumber;
linePosition = lineInfo.LinePosition;
}
return new JsonReaderException(string.Format("Unrecognized token: {0}",
reader.TokenType), reader.Path, lineNumber, linePosition, null);
}
return value;
}
private IList ReadArray(JsonReader reader, Type targetType, JsonSerializer serializer)
{
var elementType = GetElementType(targetType);
var list = CreateCompatibleList(targetType, elementType);
while (reader.Read() && reader.TokenType != JsonToken.EndArray)
{
list.Add(ReadJson(reader, elementType, serializer));
}
if (targetType.IsArray)
{
var array = Array.CreateInstance(targetType.GetElementType(), list.Count);
list.CopyTo(array, 0);
list = array;
}
return list;
}
private static IList CreateCompatibleList(Type targetContainerType, Type elementType)
{
IList list;
if (targetContainerType.IsArray || targetContainerType.GetTypeInfo().IsAbstract)
{
list = (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(elementType));
}
else
{
list = (IList)Activator.CreateInstance(targetContainerType);
}
return list;
}
private static Type GetElementType(Type arrayOrGenericContainer)
{
Type elementType;
if (arrayOrGenericContainer.IsArray)
{
elementType = arrayOrGenericContainer.GetElementType();
}
else
{
elementType = arrayOrGenericContainer.GenericTypeArguments[0];
}
return elementType;
}
private object ReadObject(JsonReader reader, Type objectType, JsonSerializer serializer)
{
var jObject = JObject.Load(reader);
var targetType = GetType(jObject, objectType) ?? objectType;
return _ReadJson(CreateAnotherReader(jObject, reader), targetType, null, serializer);
}
private static JsonReader CreateAnotherReader(JObject jObject, JsonReader reader)
{
var jObjectReader = jObject.CreateReader();
jObjectReader.Culture = reader.Culture;
jObjectReader.CloseInput = reader.CloseInput;
jObjectReader.SupportMultipleContent = reader.SupportMultipleContent;
jObjectReader.DateTimeZoneHandling = reader.DateTimeZoneHandling;
jObjectReader.FloatParseHandling = reader.FloatParseHandling;
jObjectReader.DateFormatString = reader.DateFormatString;
jObjectReader.DateParseHandling = reader.DateParseHandling;
return jObjectReader;
}
public Type GetType(JObject jObject, Type parentType)
{
if (_typeMappingPropertyName == null)
{
return GetTypeByPropertyPresence(jObject, parentType);
}
return GetTypeFromDiscriminatorValue(jObject, parentType);
}
private static Type GetTypeByPropertyPresence(JObject jObject, Type parentType)
{
foreach (var type in parentType.GetTypeInfo().GetCustomAttributes<KnownSubTypeWithPropertyAttribute>())
{
JToken ignore;
if (jObject.TryGetValue(type.PropertyName, out ignore))
{
return type.SubType;
}
}
return null;
}
private Type GetTypeFromDiscriminatorValue(JObject jObject, Type parentType)
{
JToken jToken;
if (!jObject.TryGetValue(_typeMappingPropertyName, out jToken)) return null;
var discriminatorValue = jToken.ToObject<object>();
if (discriminatorValue == null) return null;
var typeMapping = GetSubTypeMapping(parentType);
if (typeMapping.Any())
{
return GetTypeFromMapping(typeMapping, discriminatorValue);
}
return GetTypeByName(discriminatorValue as string, parentType);
}
private static Type GetTypeByName(string typeName, Type parentType)
{
if (typeName == null)
return null;
var insideAssembly = parentType.GetTypeInfo().Assembly;
var typeByName = insideAssembly.GetType(typeName);
if (typeByName == null)
{
var searchLocation =
parentType.FullName.Substring(0, parentType.FullName.Length - parentType.Name.Length);
typeByName = insideAssembly.GetType(searchLocation + typeName, false, true);
}
return typeByName;
}
private static Type GetTypeFromMapping(IReadOnlyDictionary<object, Type> typeMapping, object discriminatorValue)
{
var targetlookupValueType = typeMapping.First().Key.GetType();
var lookupValue = ConvertJsonValueToType(discriminatorValue, targetlookupValueType);
Type targetType;
return typeMapping.TryGetValue(lookupValue, out targetType) ? targetType : null;
}
private static Dictionary<object, Type> GetSubTypeMapping(Type type)
{
return type.GetTypeInfo().GetCustomAttributes<KnownSubTypeAttribute>()
.ToDictionary(x => x.AssociatedValue, x => x.SubType);
}
private static object ConvertJsonValueToType(object objectType, Type targetlookupValueType)
{
if (targetlookupValueType.GetTypeInfo().IsEnum)
return Enum.ToObject(targetlookupValueType, objectType);
return Convert.ChangeType(objectType, targetlookupValueType);
}
protected object _ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
_reader = reader;
_isInsideRead = true;
try
{
return serializer.Deserialize(reader, objectType);
}
finally
{
_isInsideRead = false;
}
}
}
}