结构体 生成 json

• 结构体字段首字母大写, 无标签 （正常转）
• 结构体字段首字母大写, 有标签 （正常转）
• 结构体字段首字母小写 （失败） ```go package main

import ( “encoding/json” “fmt” )

/* 结构体字段首字母大写, 无标签 / type IT struct { Company string Subjects []string IsOk bool Price float64 }

func init() { // 初始化结构体变量it it := IT{“hello”, []string{“Vue”, “React”, “Angular”}, true, 66.66}

// 根据内容生成json
buf, err := json.Marshal(it)
if err != nil {
    fmt.Println("err=", err)
    return
}
fmt.Println("buf = ", string(buf))
/**
正常转换，json key也是大写
buf =  {"Company":"hello","Subjects":["Vue","React","Angular"],"IsOk":true,"Price":66.66}
*/

}

/* 结构体字段首字母大写, 有标签 / type IT3 struct { Company string json:"company" Subjects []string json:"subjects" IsOk bool json:"isOk" Price float64 json:"price" }

func init() { // 初始化结构体变量it it3 := IT3{“hello”, []string{“Vue”, “React”, “Angular”}, true, 66.66}

// 根据内容生成json
buf, err := json.Marshal(it3)
if err != nil {
    fmt.Println("err=", err)
    return
}
fmt.Println("buf = ", string(buf))
/**
正常转换，json key 小写
buf =  {"company":"hello","subjects":["Vue","React","Angular"],"isOk":true}
*/

}

/* 结构体字段名称首字母小写 / type IT2 struct { Company string isOk bool price float64 }

func init() { // 初始化结构体变量it it2 := IT2{“hello”, true, 66.66}

// 根据内容生成json
buf, err := json.Marshal(it2)
if err != nil {
    fmt.Println("err=", err)
    return
}
fmt.Println("buf = ", string(buf))
/**
只转了大写的
buf =  {"Company":"hello"}
*/

}

func main() {

/*
buf =  {"Company":"hello","Subjects":["Vue","React","Angular"],"IsOk":true,"Price":66.66}
buf =  {"Company":"hello"}
buf =  {"company":"hello","subjects":["Vue","React","Angular"],"isOk":true}
*/

}

- 如果变量首字母小写，则为private。无论如何不能转，因为取不到反射信息。
- 如果变量首字母大写，则为public。
   - 不加tag，可以正常转为json里的字段，json内字段名跟结构体内字段原名一致。
   - 加了tag，从struct转json的时候，json的字段名就是tag里的字段名，原字段名已经没用。
<a name="eXCF8"></a>
# map 生成 json
```go
package main
import (
    "encoding/json"
    "fmt"
)
func main()  {
    /**
    mapName := map[keyType]valueType
    */
    bookInfo := make(map[string]interface{}, 4)
    bookInfo["company"] ="hello"
    bookInfo["subjects"] = []string{"Go", "C++", "C"}
    bookInfo["isOk"] = true
    bookInfo["price"] = 666.666
    result, err := json.MarshalIndent(bookInfo, "", "  ")
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Println("result = ", string(result))
    /**
    result =  {
      "company": "hello",
      "isOk": true,
      "price": 666.666,
      "subjects": [
        "Go",
        "C++",
        "C"
      ]
    }
    */
}

json 生成 结构体

package main
import (
    "encoding/json"
    "fmt"
)
func init() {
    // 有无tag 都会成功
    type Front struct {
        Company     string         `json:"company"`
        Subjects     []string    `json:"subjects"`
        IsOk        bool        `json:"isOk"`
        Price         float64        `json:"price"`
    }
    frontBuf := `{
        "company": "hello",
        "subjects": ["Vue","React","Angular"],
        "isOk": true,
        "price": 66.66
    }`
    var front Front
    err := json.Unmarshal([]byte(frontBuf), &front)
    if (err != nil) {
        fmt.Println("err = ", err)
        return
    }
    fmt.Printf("front = %+v\n", front)
    fmt.Println("front =  ", front)
    fmt.Println("front.Subjects:: ", front.Subjects)
    /*
    front = {Company:hello Subjects:[Vue React Angular] IsOk:true Price:66.66}
    front =   {hello [Vue React Angular] true 66.66}
    front.Subjects::  [Vue React Angular]
    */
}
func main() {
}

json 生成 map

package main
import (
    "encoding/json"
    "fmt"
)
func init() {
    frontBuf := `{
        "company": "hello",
        "subjects": ["Vue","React","Angular"],
        "isOk": true,
        "price": 66.66
    }`
    list := make(map[string]interface{}, 4)
    err := json.Unmarshal([]byte(frontBuf), &list)
    if (err != nil) {
        fmt.Println("err = ", err)
        return
    }
    fmt.Printf("front = %+v\n", list)
    fmt.Println("front =  ", list)
    /*
    front = map[company:hello isOk:true price:66.66 subjects:[Vue React Angular]]
    front =   map[company:hello isOk:true price:66.66 subjects:[Vue React Angular]]
    */
    for key, value := range list {
        switch data := value.(type) {
        case string:
            print(key, value, data)
        case bool:
            print(key, value, data)
        case float64:
            print(key, value, data)
        case []string:
            print(key, value, data)
        case []interface{}:
            print(key, value, data)
        }
    }
    /*
    list[company]   type is string                  value:  hello
    list[subjects]  type is []interface {}          value:  [Vue React Angular]
    list[isOk]      type is bool                    value:  true
    list[price]     type is float64                 value:  66.66
    */
}
func print(key interface{}, value interface{}, data interface{}) {
    fmt.Printf("list[%s]     type is %T", key, value)
    fmt.Printf("            value:  %v \n", value)
}
func main() {
}