[ Golang ] JSON Object 키 넣은 순서대로 정렬하기

Golang 에서는 일반적인 JsonMarshal 을 통한 encoding 은 키순서 오름차순으로 encoding 이 되게끔 되어있다.

사실 Object 에는 키순서는 따로 중요하지 않지만 Object 키가 저장된 그대로 나와야하는 상황이 있으면 다음과 같은 로직이 필요하다.

 

package order_json_object

import (
	"bytes"
	"encoding/json"
)

type OrderJsonMap struct {
	Order []string
	Map   map[string]string
}

func (om OrderJsonMap) MarshalJSON() ([]byte, error) {
	var b []byte
	buf := bytes.NewBuffer(b)
	buf.WriteRune('{')
	l := len(om.Order)
	for i, key := range om.Order {
		km, err := json.Marshal(key)
		if err != nil {
			return nil, err
		}
		buf.Write(km)
		buf.WriteRune(':')
		vm, err := json.Marshal(om.Map[key])
		if err != nil {
			return nil, err
		}
		buf.Write(vm)
		if i != l-1 {
			buf.WriteRune(',')
		}
	}
	buf.WriteRune('}')
	return buf.Bytes(), nil
}


package order_json_object_test

import (
	"encoding/json"
	"github.com/hoyeonUM/golang-example/order_json_object"
	"github.com/stretchr/testify/assert"
	"testing"
)

func TestConcurrent(t *testing.T) {
	t.Run(`given string map first key is b and second key is a when parse json then first key is a and second key is b`, func(t *testing.T) {
		notOrderJson := make(map[string]string)
		notOrderJson["b"] = "bbb"
		notOrderJson["a"] = "aaa"
		b, _ := json.Marshal(notOrderJson)
		assert.Equal(t, `{"a":"aaa","b":"bbb"}`, string(b))
	})

	t.Run(`given string map first key is b and second key is a when parse order json then first key is b and second key is a`, func(t *testing.T) {
		notOrderJson := make(map[string]string)
		notOrderJson["b"] = "bbb"
		notOrderJson["a"] = "aaa"

		OrderJson := order_json_object.OrderJsonMap{}
		OrderJson.Order = []string{"b", "a"}
		OrderJson.Map = notOrderJson
		b, _ := json.Marshal(OrderJson)
		assert.Equal(t, `{"b":"bbb","a":"aaa"}`, string(b))
	})
}

 

참고문서 : https://stackoverflow.com/questions/48293036/prevent-alphabetically-ordering-json-at-marshal