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golang struct, map, json之间的相互转换

公共代码区域

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": "酒窝猪",
 "address":   []map[string]interface{}{{"address": "address01"}, {"address": "address02"}},
}

var User UserInfoVo

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

一、map, struct 互转

1.map 转 struct

map 转 struct 有两种方式
1.是通过第三方包 github.com/mitchellh/mapstructure
2.通过 map 转 json，再通过 json 转 struct

第三方包 mapstructure

下载依赖，通过第三方依赖进行转换

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

通过 JSON 进行转换

先将 map 转换成 JSON，再通过 JSON 转换成 struct
操作有点繁琐

func TestMapToStructByJson(t *testing.T) {
 beforeMap := map[string]interface {}{
  "id":"123",
  "user_name":"酒窝猪",
  "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:酒窝猪 Address:[{Address:address01} {Address:address02}]}--- PASS: TestMapToStructByJson (0.00s)
PASS

总结
问题：
论性能哪个更佳？

根据结果答案
使用 JSON 需要时间是 134.299µs
使用 mapstructure 需要时间是 61.757µs
结果是使用第三方包 mapstructure 性能更好，那么，是因为什么呢？暂且按下不表

2、struct 转 map

JSON 序列化转换

先将 struct 转换成字节数组，再将字节数组转换成 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:酒窝猪]--- PASS: TestStructToMapByJson (0.00s)
PASS

通过反射转换

通过反射获取 User 的类型与值

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:酒窝猪]--- PASS: TestStructToMapByReflect (0.00s)
PASS

总结
问题：论性能哪个更佳？

答案是使用反射的效果更快点，没有那么多繁琐的转换，记住在 make 中进行初始化大小，我试了下，不指定大小与指定大小时间上有 3~4µs 的区别
网络上还有一种方法是使用 structs 包，不过我看了下，该依赖包已经三年没更新了

二、struct, json 互转

1. struct 转 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":"酒窝猪","address":[{"address":"湖南"},{"address":"北京"}]}--- PASS: TestStructToJsonByJson (0.00s)
PASS

2.json 转 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:酒窝猪 Address:[{Address:湖南} {Address:北京}]}--- PASS: TestJsonToStructByJson (0.00s)
PASS

三、map, json 互转

1.map 转 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":"酒窝猪"}--- PASS: TestMapToJson (0.00s)
PASS

2.json 转 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)
}