I created a JSON schema for my C# code using:
// Create JSON schema
var generator = new JSchemaGenerator();
var schema = generator.Generate(typeof(ConfigFileJsonSchema));
schema.Title = "PlexCleaner Schema";
schema.Description = "PlexCleaner config file JSON schema";
schema.SchemaVersion = new Uri("http://json-schema.org/draft-06/schema");
schema.Id = new Uri("https://raw.githubusercontent.com/ptr727/PlexCleaner/main/PlexCleaner.schema.json");
Console.WriteLine(schema);
I want to add a reference to this scheme whenever I create JSON output from my code:
private static string ToJson(ConfigFileJsonSchema settings)
{
return JsonConvert.SerializeObject(settings, Settings);
}
private static readonly JsonSerializerSettings Settings = new()
{
Formatting = Formatting.Indented,
StringEscapeHandling = StringEscapeHandling.EscapeNonAscii,
NullValueHandling = NullValueHandling.Ignore,
// We expect containers to be cleared before deserializing
// Make sure that collections are not read-only (get; set;) else deserialized values will be appended
// https://stackoverflow.com/questions/35482896/clear-collections-before-adding-items-when-populating-existing-objects
ObjectCreationHandling = ObjectCreationHandling.Replace
// TODO: Add TraceWriter to log to Serilog
};
How can I programmatically add the $schema
URI to the created JSON, not meaning creating schema on the fly, but something like this:
public class ConfigFileJsonSchemaBase
{
// Schema reference
[JsonProperty(PropertyName = "$schema", Order = -2)]
public string Schema { get; } = "https://raw.githubusercontent.com/ptr727/PlexCleaner/main/PlexCleaner.schema.json";
// Default to 0 if no value specified, and always write the version first
[DefaultValue(0)]
[JsonProperty(DefaultValueHandling = DefaultValueHandling.Populate, Order = -2)]
public int SchemaVersion { get; set; } = ConfigFileJsonSchema.Version;
}
Without needing to add a $schema
entry to the class.
E.g. equivalent of:
schema.SchemaVersion = new Uri("http://json-schema.org/draft-06/schema");
There is a similar unanswered question: json serialization to refer schema
CodePudding user response:
You can use a JsonConverter:
public class SchemaJsonConverter : JsonConverter
{
private readonly string _schemaUrl;
private readonly Type[] _types;
public SchemaJsonConverter(string schemaUrl, params Type[] types)
{
this._schemaUrl = schemaUrl;
this._types = types;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
JToken t = JToken.FromObject(value);
if (t.Type != JTokenType.Object)
{
t.WriteTo(writer);
}
else
{
var o = (JObject)t;
o.AddFirst(new JProperty("$Schema", this._schemaUrl));
o.WriteTo(writer);
}
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException("Unnecessary because CanRead is false. The type will skip the converter.");
}
public override bool CanRead
{
get { return false; }
}
public override bool CanConvert(Type objectType)
{
return this._types.Any(t => t == objectType);
}
}
You need the type to check the types affected by the converter and the schema url to inject it in your JSON. The converter allow you a fine control about the process of serialization.
I use a simple class to test the converter:
public class Something
{
public int Integer { get; set; }
public string Text { get; set; }
}
And a method to run the sample:
public static void Test()
{
var something = new Something
{
Integer = 37,
Text = "A text"
};
var settings = new JsonSerializerSettings
{
Formatting = Formatting.Indented,
StringEscapeHandling = StringEscapeHandling.EscapeNonAscii,
NullValueHandling = NullValueHandling.Ignore,
// We expect containers to be cleared before deserializing
// Make sure that collections are not read-only (get; set;) else deserialized values will be appended
// https://stackoverflow.com/questions/35482896/clear-collections-before-adding-items-when-populating-existing-objects
ObjectCreationHandling = ObjectCreationHandling.Replace
// TODO: Add TraceWriter to log to Serilog
};
var schemaUrl = "http://json-schema.org/draft-06/schema";
settings.Converters.Add(new SchemaJsonConverter(schemaUrl, something.GetType()));
var json = JsonConvert.SerializeObject(something, settings);
Console.WriteLine(json);
}
Output:
{
"$Schema": "http://json-schema.org/draft-06/schema",
"Integer": 37,
"Text": "A text"
}
UPDATE
A static method for serialization:
public static string SerializeJson(object obj, JsonSerializerSettings settings, string schemaUrl = null)
{
if (!string.IsNullOrEmpty(schemaUrl))
{
settings.Converters.Add(new SchemaJsonConverter(schemaUrl, obj.GetType()));
}
return JsonConvert.SerializeObject(obj, settings);
}
Usage:
var json = SerializeJson(something, settings, schemaUrl);