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golang struct, map, json之間的相互轉換

公共代碼區域

package main

import (
 "encoding/json"
 "fmt"
 "testing"
)

type UserInfoVo struct {
 Id   string `json:"id"`
 UserName string `json:"user_name"`
 Address []AddressVo `json:"address"`
}

type AddressVo struct {
 Address string `json:"address"`
}

var beforeMap = map[string]interface{}{
 "id":        "123",
 "user_name": "酒窩豬",
 "address":   []map[string]interface{}{{"address": "address01"}, {"address": "address02"}},
}

var User UserInfoVo

func init() {
 User = UserInfoVo{
  Id:       "01",
  UserName: "酒窩豬",
  Address: []AddressVo{
   {
    Address: "湖南",
   },
   {
    Address: "北京",
   },
  },
 }
}

一、map, struct 互轉

1.map 轉 struct

map 轉 struct 有兩種方式
1.是通過第三方包 github.com/mitchellh/mapstructure
2.通過 map 轉 json，再通過 json 轉 struct

第三方包 mapstructure

下載依賴，通過第三方依賴進行轉換

go get github.com/goinggo/mapstructure

func TestMapToStructByMod(t *testing.T) {
 var afterStruct =UserInfoVo{}
 before := time.Now()
 err := mapstructure.Decode(beforeMap, afterStruct)
 if err!=nil{
  fmt.Println(err)
 }
 fmt.Printf("result:%+v \n",time.Since(before))
 fmt.Printf("result:%+v \n",afterStruct)
}

result:61.757µs
result:{Id:123 UserName: Address:[{Address:address01} {Address:address02}]}
--- PASS: TestMapToStructByMod (0.00s)
PASS

通過 JSON 進行轉換

先將 map 轉換成 JSON，再通過 JSON 轉換成 struct
操作有點繁瑣

func TestMapToStructByJson(t *testing.T) {
 beforeMap := map[string]interface {}{
  "id":"123",
  "user_name":"酒窩豬",
  "address":[]map[string]interface{}{{"address": "address01"}, {"address": "address02"}},
 }
 var afterStruct =UserInfoVo{}
 before := time.Now()
 marshal, err := json.Marshal(beforeMap)
 if err!=nil{
  fmt.Println("marshal:",err)
  return
 }
 err = json.Unmarshal(marshal, afterStruct)
 if err!=nil{
  fmt.Println("unmarshal:",err)
  return
 }
 fmt.Println(time.Since(before))
 fmt.Printf("resutlt: %+v",afterStruct)
}

134.299µs
resutlt: {Id:123 UserName:酒窩豬 Address:[{Address:address01} {Address:address02}]}--- PASS: TestMapToStructByJson (0.00s)
PASS

總結
問題：
論性能哪個更佳？

根據結果答案
使用 JSON 需要時間是 134.299µs
使用 mapstructure 需要時間是 61.757µs
結果是使用第三方包 mapstructure 性能更好，那么，是因為什么呢？暫且按下不表

2、struct 轉 map

JSON 序列化轉換

先將 struct 轉換成字節數組，再將字節數組轉換成 map 打印

func TestStructToMapByJson(t *testing.T) {
 var resultMap interface{}
 before := time.Now()
 jsonMarshal, _ := json.Marshal(User)
 err := json.Unmarshal(jsonMarshal, resultMap)
 if err != nil {
  fmt.Println(err)
  return
 }
 fmt.Println(time.Since(before))
 fmt.Printf("%+v",resultMap)
}

158.857µs
map[address:[map[address:湖南] map[address:北京]] id:01 user_name:酒窩豬]--- PASS: TestStructToMapByJson (0.00s)
PASS

通過反射轉換

通過反射獲取 User 的類型與值

func TestStructToMapByReflect(t *testing.T) {
 var resultMap = make(map[string]interface{},10)
 before := time.Now()

 ty:=reflect.TypeOf(User)
 v:=reflect.ValueOf(User)
 for i := 0; i  v.NumField(); i++ {
  resultMap[strings.ToLower(ty.Field(i).Name)]=v.Field(i).Interface()
 }
 fmt.Println(time.Since(before))
 fmt.Printf("%+v",resultMap)
}

13.965µs
map[address:[{Address:湖南} {Address:北京}] id:01 username:酒窩豬]--- PASS: TestStructToMapByReflect (0.00s)
PASS

總結
問題：論性能哪個更佳？

答案是使用反射的效果更快點，沒有那么多繁瑣的轉換，記住在 make 中進行初始化大小，我試了下，不指定大小與指定大小時間上有 3~4µs 的區別
網絡上還有一種方法是使用 structs 包，不過我看了下，該依賴包已經三年沒更新了

二、struct, json 互轉

1. struct 轉 json

func TestStructToJsonByJson(t *testing.T) {
 before := time.Now()
 marshal, _ := json.Marshal(User)
 fmt.Println(time.Since(before))
 fmt.Printf("%s", marshal)
}

116.068µs
{"id":"01","user_name":"酒窩豬","address":[{"address":"湖南"},{"address":"北京"}]}--- PASS: TestStructToJsonByJson (0.00s)
PASS

2.json 轉 struct

func TestJsonToStructByJson(t *testing.T) {
 info:=UserInfoVo{}
 marshal, _ := json.Marshal(User)
 before := time.Now()
 json.Unmarshal(marshal,info)
 fmt.Println(time.Since(before))
 fmt.Printf("%+v",info)
}

23.009µs
{Id:01 UserName:酒窩豬 Address:[{Address:湖南} {Address:北京}]}--- PASS: TestJsonToStructByJson (0.00s)
PASS

三、map, json 互轉

1.map 轉 json

func TestMapToJson(t *testing.T) {
 before := time.Now()
 marshal, _ := json.Marshal(beforeMap)
 fmt.Println(time.Since(before))
 fmt.Printf("%s", marshal)
}

75.133µs
{"address":[{"address":"address01"},{"address":"address02"}],"id":"123","user_name":"酒窩豬"}--- PASS: TestMapToJson (0.00s)
PASS

2.json 轉 map

func TestJsonToMap(t *testing.T) {
 marshal, _ := json.Marshal(beforeMap)
 resultMap:=make(map[string]interface{},10)
 before := time.Now()
 json.Unmarshal(marshal,resultMap)
 fmt.Println(time.Since(before))
 fmt.Printf("%+v", resultMap)
}