go

结构体与json相互转换，map与json相互转换

目录
  1. 1. 一.结构体转json，使用json.Marshal()返回值([]byte, error)
  2. 2. 二.json转结构体，使用json.Unmarshal([]byte(string),*s)
  3. 3. 三.map转json
  4. 4. 四.json转map，数字默认为float64

一.结构体转json，使用json.Marshal()返回值([]byte, error)

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package main

import (
    "encoding/json"
    "fmt"
)

type Student struct {
    Name string
    Age int
    Gender byte
    Subject []string
}

func main() {
    s := Student{
        "XiaoMing",
        15,
        'M',
        []string{"数学","语文","英语"},
    }
    sJson,err := json.Marshal(s)
    if err!=nil{
        fmt.Println(err)
        return
    }
    fmt.Println("json of s = ",string(sJson))
}

运行结果：

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json of s =  {"Name":"XiaoMing","Age":15,"Gender":77,"Subject":["数学","语文","英语"]}

二.json转结构体，使用json.Unmarshal([]byte(string),*s)

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package main

import (
    "encoding/json"
    "fmt"
)

type Student struct {
    Name string  //`json:"-"` 字段转换成json时舍弃
    Age int
    Gender byte
    Subject []string
}
func main() {
    str := `{
        "name":"李雷",
        "age": "15",
        "gender": 77,
        "subject": [
            "数学",
            "语文",
            "英语"
        ]
    }`
    s:= new(Student)
    err := json.Unmarshal([]byte(str), &s)//第二个参数必须是指针
    if err != nil{
        fmt.Println(err)
        return
    }
    fmt.Println(s)
}

运行结果：

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{李雷 0 77 [数学 语文 英语]}

三.map转json

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package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    m := make(map[string]interface{})
    m["name"] = "HanMeimei"
    m["age"] = 11
    m["gender"] = 'M'
    m["subject"] = []string{"语文","数学","英语"}
    fmt.Println("m = ",m)
    mJson,err := json.Marshal(m)
    if err!=nil {
        fmt.Println(err)
        return
    }
    fmt.Printf("mJson = %s",mJson)

}

运行结果：

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m =  map[age:11 gender:77 name:HanMeimei subject:[语文 数学 英语]]
mJson = {"age":11,"gender":77,"name":"HanMeimei","subject":["语文","数学","英语"]}

四.json转map，数字默认为float64

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package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    mJson := `{"age":11,"gender":77,"name":"HanMeimei","subject":["语文","数学","英语"]}`
    m:=make(map[string]interface{})
    json.Unmarshal([]byte(mJson),&m)
    fmt.Println(m)

    // map值不能直接使用
    // fmt.Println(m["company"])
    // 报错：cannot use m["company"] (type interface {}) as type string in assignment: need type assertion
    // 需要使用断言处理后才能使用
    // fmt.Println(m["company"].(string))

    //类型断言
    for key,value := range m{
        switch value.(type){
        case string:
            fmt.Printf("m[%s] = %s,type = string\n",key,value)
        case int:
            fmt.Printf("m[%s] = %d,type = int\n",key,value)
        case float64:
            fmt.Printf("m[%s] = %f,type = float64\n",key,value)
        case []interface{}:
            fmt.Printf("m[%s] = %s,type = []interface{}\n",key,value)
        case byte:
            fmt.Printf("m[%s] = %s,type = byte\n",key,value)
        }
    }
}

运行结果：

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map[age:11 gender:77 name:HanMeimei subject:[语文 数学 英语]]
m[name] = HanMeimei,type = string
m[subject] = [语文 数学 英语],type = []interface{}
m[age] = 11.000000,type = float64
m[gender] = 77.000000,type = float64