Json データ を interface{} でパース後, 再び文字列に戻す際のパーサー

convertMapToStr.go

import (
  "log"
  "reflect"
  "strconv"
)

func convertMapToStr(jsonData interface{}) string {
	l := []string{}
	for key, val := range jsonData.(map[interface{}]interface{}) {
		switch reflect.ValueOf(val).Kind() {
		case reflect.String:
			l = append(l, "\"" + key.(string) + "\":\"" + val.(string) + "\"")
		case reflect.Bool:
			l = append(l, "\"" + key.(string) + "\":" + strconv.FormatBool(val.(bool)))
		case reflect.Int:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(val.(int)))
		case reflect.Int8:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(int8))))
		case reflect.Int16:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(int16))))
		case reflect.Int32:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(int32))))
		case reflect.Int64:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(int64))))
		case reflect.Uint8:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(uint8))))
		case reflect.Uint16:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(uint16))))
		case reflect.Uint32:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(uint32))))
		case reflect.Uint64:
			l = append(l, "\"" + key.(string) + "\":" + strconv.Itoa(int(val.(uint64))))
		case reflect.Float64:
			// NaN, Inf に備えてちゃんとパースする
			l = append(l, "\"" + key.(string) + "\":" + strconv.FormatFloat(val.(float64), 'G', 3, 64))
		case reflect.Map:
			v := convertMapToStr(val)
			l = append(l, "\"" + key.(string) + "\":" + v)
		default:
			if val == nil {
				l = append(l, "\"" + key.(string) + "\":\"\"")
			} else {
        log.Println("Other type: %v", val)
			}
		}
	}

	joined := strings.Join(l, ",")
	joined = "{" + joined + "}"

	return joined
}

Kinesis の fluentd データを lambda で処理する際に使用.
ProtocolBuffer を変換してきたのでテキスト形式の Json データはなかった.
ログなので入れ子になっており, 階層の深さも一定ではないため再帰で内部の Map も取得.
(多くても5層くらい)