How can I make the link handling syntax with Jackson and JSON.net compatible?
I have a server that creates the following JSON with Jackson.
{
"$id" : 1,
"employees" : [
{
"$id" : 2,
"name" : "John Rambo",
},
2 // Jackson: reference by ID only
]
}
The employee list contains the same employee twice. Jackson correctly references the object by ID a second time.
I want to deserialize this in a client that is using JSON.net, but that doesn't work because JSON.net expects me to have a link wrapped in a json object with a $ ref property like this:
{
"$id": "1",
"employees" : [
{
"$id": "2",
"name": "John Rambo"
},
{
"$ref": "2" // JSON.net: reference wrapped in JSON object
}
]
}
Is there a way to get JSON.net to use Jackson's syntax correctly, either by configuration or by creating a custom deserializer?
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Here's a custom converter that should work:
public class EmployeeConverter : JsonConverter
{
public override void WriteJson(
JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
public override object ReadJson(
JsonReader reader,
Type objectType,
object existingValue,
JsonSerializer serializer)
{
List<Employee> employees = null;
if (reader.TokenType == JsonToken.StartArray)
{
JArray arr = serializer.Deserialize<JArray>(reader);
employees = new List<Employee>(arr.Count);
var employeeMap = new Dictionary<int, Employee>();
foreach (var item in arr)
{
if (item.Type == JTokenType.Object)
{
var employee = item.ToObject<Employee>();
employees.Add(employee);
int id = item["$id"].ToObject<int>();
employeeMap.Add(id, employee);
}
else if (item.Type == JTokenType.Integer)
{
Employee employee = null;
int id = item.ToObject<int>();
if (employeeMap.TryGetValue(id, out employee))
{
employees.Add(employee);
}
}
}
}
return employees;
}
public override bool CanRead
{
get { return true; }
}
public override bool CanConvert(Type objectType)
{
return false;
}
}
... and this is how you use it:
public class Company
{
public Company()
{
this.Employees = new List<Employee>();
}
[JsonConverter(typeof(EmployeeConverter))]
public List<Employee> Employees { get; set; }
}
Example: https://dotnetfiddle.net/XooyQC
Basically use your own converter to deserialize the whole array. First we deserialize the array to JArray
, then we check each element JArray
to see if it is a reference or a new object.
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