9f0beec63aWe try hard to avoid creating unnecessary JsonSerializerOptions, as each can have a non-trivial overhead due to how reflection is used by JsonSerializer and the JSO instance serving as a cache. Rather than creating a new JSO for each transport / endpoint, this can just use a singleton. The only thing it loses is logging when the converter fails, but all of those paths are also throwing an exception, which can be logged higher in the call stack.
90 lines
No EOL
3.3 KiB
C#
90 lines
No EOL
3.3 KiB
C#
using System.Text.Json;
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using System.Text.Json.Serialization;
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using McpDotNet.Protocol.Messages;
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using Microsoft.Extensions.Logging;
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using McpDotNet.Logging;
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namespace McpDotNet.Utils.Json;
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/// <summary>
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/// JSON converter for IJsonRpcMessage that handles polymorphic deserialization of different message types.
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/// </summary>
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internal sealed class JsonRpcMessageConverter : JsonConverter<IJsonRpcMessage>
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{
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/// <inheritdoc/>
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public override IJsonRpcMessage? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
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{
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if (reader.TokenType != JsonTokenType.StartObject)
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{
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throw new JsonException("Expected StartObject token");
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}
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using var doc = JsonDocument.ParseValue(ref reader);
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var root = doc.RootElement;
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// All JSON-RPC messages must have a jsonrpc property with value "2.0"
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if (!root.TryGetProperty("jsonrpc", out var versionProperty) ||
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versionProperty.GetString() != "2.0")
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{
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throw new JsonException("Invalid or missing jsonrpc version");
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}
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// Determine the message type based on the presence of id, method, and error properties
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bool hasId = root.TryGetProperty("id", out _);
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bool hasMethod = root.TryGetProperty("method", out _);
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bool hasError = root.TryGetProperty("error", out _);
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var rawText = root.GetRawText();
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// Messages with an id but no method are responses
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if (hasId && !hasMethod)
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{
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// Messages with an error property are error responses
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if (hasError)
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{
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return JsonSerializer.Deserialize<JsonRpcError>(rawText, options);
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}
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// Messages with a result property are success responses
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else if (root.TryGetProperty("result", out _))
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{
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return JsonSerializer.Deserialize<JsonRpcResponse>(rawText, options);
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}
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throw new JsonException("Response must have either result or error");
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}
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// Messages with a method but no id are notifications
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else if (hasMethod && !hasId)
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{
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return JsonSerializer.Deserialize<JsonRpcNotification>(rawText, options);
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}
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// Messages with both method and id are requests
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else if (hasMethod && hasId)
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{
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return JsonSerializer.Deserialize<JsonRpcRequest>(rawText, options);
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}
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throw new JsonException("Invalid JSON-RPC message format");
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}
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/// <inheritdoc/>
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public override void Write(Utf8JsonWriter writer, IJsonRpcMessage value, JsonSerializerOptions options)
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{
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switch (value)
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{
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case JsonRpcRequest request:
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JsonSerializer.Serialize(writer, request, options);
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break;
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case JsonRpcNotification notification:
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JsonSerializer.Serialize(writer, notification, options);
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break;
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case JsonRpcResponse response:
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JsonSerializer.Serialize(writer, response, options);
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break;
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case JsonRpcError error:
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JsonSerializer.Serialize(writer, error, options);
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break;
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default:
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throw new JsonException($"Unknown JSON-RPC message type: {value.GetType()}");
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}
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}
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} |