protoc-gen-go-json

This is a plugin for the Google Protocol Buffers compiler protoc that generates code to implement json.Marshaler and json.Unmarshaler using protojson.

This enables Go-generated protobuf messages to be embedded directly within other structs and encoded with the standard JSON library, since the standard encoding/json library can't encode certain protobuf messages such as those that contain oneof fields.

Install

go get github.com/mitchellh/protoc-gen-go-json

Also required:

• protoc
• protoc-gen-go

Usage

Define your messages like normal:

syntax = "proto3";

message Request {
  oneof kind {
    string name = 1;
    int32  code = 2;
  }
}

The example message purposely uses a oneof since this won't work by default with encoding/json. Next, generate the code:

protoc --go_out=. --go-json_out=. request.proto

Your output should contain a file request.pb.json.go which contains the implementation of json.Marshal/Unmarshal for all your message types. You can then encode your messages using standard encoding/json:

import "encoding/json"

// Marshal
bs, err := json.Marshal(&Request{
  Kind: &Kind_Name{
    Name: "alice",
  },
}

// Unmarshal
var result Request
json.Unmarshal(bs, &result)

Options

The generator supports options you can specify via the command-line:

• enums_as_ints={bool} - Render enums as integers instead of strings.
• emit_defaults={bool} - Render fields with zero values.
• orig_name={bool} - Use original (.proto file) name for fields.
• allow_unknown={bool} - Allow messages to contain unknown fields when unmarshaling

It also includes the "standard" options available to all protogen-based plugins:

• import_path={path} - Override the import path
• paths=source_relative - Derive the output path from the input path
• etc.

These can be set as part of the --go-json_out value:

protoc --go-json_opt=emit_defaults=true:.

You can specify multiple using a ,:

protoc --go-json_out=enums_as_ints=true,emit_defaults=true:.

Alternatively, you may also specify options using the --go-json_opt value:

protoc --go-json_out:. --go-json_opt=emit_defaults=true,enums_as_ints=true