Protobuf.System.Text.Json

This library provides support for Google.Protobuf types to System.Text.Json.

By default classes generated from *.proto files don't work well with System.Text.Json. You can properly serialize and deserialize only very simple contracts (only scalar value types work properly). When your schema contains some more advanced structures like repeated fields, maps, oneofs, or optional fields the results are far from acceptable.

You may try to write a custom JsonConverter that will utilize JsonFormatter and JsonParser from Google.Protobuf package to do all the heavy lifting. Unfortunately, this solution falls short in terms of performance. This library provides high-performance and low-allocating types that serialize Google.Protobuf objects to JavaScript Object Notation (JSON) text and deserialize JSON text to Google.Protobuf objects.

Quickstart

Add Protobuf.System.Text.Json NuGet package to your project using dotnet CLI:

dotnet add package Protobuf.System.Text.Json

To enable Protobuf support you need to register it on JsonSerializerOptions:

var jsonSerializerOptions = new JsonSerializerOptions();
jsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
jsonSerializerOptions.AddProtobufSupport();

You need to pass the options each time you want to serialize:

var msg = new SimpleMessage
{
    DoubleProperty = 2.5d
};
var payload = JsonSerializer.Serialize(msg, options: jsonSerializerOptions);

or deserialize Google.Protobuf objects:

var deserialized = JsonSerializer.Deserialize<SimpleMessage>(payload, jsonSerializerOptions);

Configuration

The library offers several configuration options to fine-tune protobuf serialization. You can modify the default settings using a delegate passed to the AddProtobufSupport method. The available options are described below:

UseProtobufJsonNames

This option defines how property names should be resolved for protobuf contracts. When set to true, the PropertyNamingPolicy will be ignored, and property names will be derived from the protobuf contract. The default value is false.

TreatDurationAsTimeSpan

This option controls how Google.Protobuf.WellKnownTypes.Duration fields are handled. When set to true, Google.Protobuf.WellKnownTypes.Duration properties will be converted to TimeSpan before serialization and will be expected in the same format as TimeSpan during deserialization. The default value is true.

TreatTimestampAsDateTime

This option controls how Google.Protobuf.WellKnownTypes.Timestamp fields are handled. When set to true, Google.Protobuf.WellKnownTypes.Timestamp properties will be converted to DateTime before serialization and will be expected in the same format as DateTime during deserialization. The default value is true.`

UseStringProtoEnumValueNames

By settingUseStringProtoEnumValueNames to true, the library will serialize enum values using the names specified in the .proto file and expect the same format during deserialization. The default value is false.

By customizing these options, you can control how the library handles various aspects of protobuf serialization and deserialization, ensuring the JSON output is consistent with your requirements.

Performance

BenchmarkDotNet v0.13.12, macOS Sonoma 14.5 (23F79) [Darwin 23.5.0]
Apple M1 Pro, 1 CPU, 10 logical and 10 physical cores
.NET SDK 8.0.100
  [Host]     : .NET 8.0.0 (8.0.23.53103), Arm64 RyuJIT AdvSIMD
  DefaultJob : .NET 8.0.0 (8.0.23.53103), Arm64 RyuJIT AdvSIMD

Simple message

Method	Mean	Error	StdDev
SystemTextJsonProtobufSupport	1.562 us	0.0080 us	0.0074 us
NewtonsoftJsonWithProtobufParserAndFormatter	8.705 us	0.0432 us	0.0383 us

Message with oneofs

Method	Mean	Error	StdDev
SystemTextJsonProtobufSupport	1.832 us	0.0132 us	0.0117 us
NewtonsoftJsonWithProtobufParserAndFormatter	9.962 us	0.1668 us	0.1561 us

Message with repeated fields

Method	Mean	Error	StdDev
SystemTextJsonProtobufSupport	53.79 us	0.262 us	0.232 us
NewtonsoftJsonWithProtobufParserAndFormatter	340.94 us	1.360 us	1.205 us

License

This project uses MIT licence. Long story short - you are more than welcome to use it anywhere you like, completely free of charge and without oppressive obligations.