Go语言学习: json 文件解析

用 go 语言解析 json 文件的笔记

JSON 是什么

JSON is short for JavaScript Object Notation, a widely-used data interchange format. JSON is an extremely useful data format and is used almost everywhere today.

GO语言里的JSON支持

bool for boolean data.
string for strings.
float64 for numbers.
nil for null values.

序列化/反序列化

json.Marshal: 将 go 的相关对象，转成 json 字符串
json.Unmarshal: 将 json 字符串转成 go 对象

代码

Repo: https://github.com/aric-notes/golang-notes
./golang-notes/src/2022-08/2022-08-24

Marshaling Structs to JSON
将 go Book 数组，转化为 json 字符串，未指定将大写的 Key 转成小写的 key

package main

import (
	"encoding/json"
	"fmt"
)

type Book struct {
	Name   string
	Author string
}

func main() {
	book := Book{"C++ programming language", "Bjarne Stroutsrup"}
	// 将 go 对象转成 json 字符串
	res, err := json.Marshal(book)

	if err != nil {
		fmt.Println(err)
	}

	fmt.Println(string(res)) // {"Name":"C++ programming language","Author":"Bjarne Stroutsrup"}
}

Unmarshaling JSON in Go
将一个 JSON 字符串，转化为 Go 对象

package main

import (
	"encoding/json"
	"fmt"
)

type Game struct {
	Name   string
	Rating float64
}

func main() {
	codString := `{"Name": "Call of Duty", "Rating": 8.4}`

	var cod Game

	err := json.Unmarshal([]byte(codString), &cod)

	if err != nil {
		fmt.Println(err)
	}

	fmt.Printf("%+v\n", cod) // {Name:Call of Duty Rating:8.4}
}

JSON arrays in Go Programming
JSON 数组的情况，需要自定义结构体，Array 的 Item

package main

import (
	"encoding/json"
	"fmt"
)

type Software struct {
	Name      string
	Developer string
}

func main() {
	softwaresJson := `[{"Name": "AutoCAD","Developer": "Autodesk"},{"Name": "Firefox","Developer": "Mozilla"},{"Name": "Chrome","Developer": "Google"}]`
	var softwares []Software
	err := json.Unmarshal([]byte(softwaresJson), &softwares)
	if err != nil {
		panic(err)
	}
	fmt.Println(softwares)
}

Slice to JSON in GoLang
切片，在 go 语言里的处理

package main

import (
	"encoding/json"
	"fmt"
)

type App struct {
	Name string
}

func main() {
	apps := []App{
		{Name: "Google Play"},
		{Name: "Evernote"},
		{Name: "Buffer"},
	}

	appsJson, err := json.Marshal(apps)

	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(string(appsJson)) // [{"Name":"Google Play"},{"Name":"Evernote"},{"Name":"Buffer"}]
}

修改 json 的 key

type Book struct {
    Name string `json:"title"`
    Author Author `json:"author"`
}

任意类型

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	unstructuredJson := `{"os": {"Windows": "Windows OS","Mac": "OSX","Linux": "Ubuntu"},"compilers": "gcc"}`

	var result map[string]any

	json.Unmarshal([]byte(unstructuredJson), &result)

	fmt.Println(result["os"]) // map[Linux:Ubuntu Mac:OSX Windows:Windows OS]
}

实例: 读取一个 json 文件

users.json

{
  "users": [
    {
      "name": "Elliot",
      "type": "Reader",
      "age": 23,
      "social": {
        "facebook": "https://facebook.com",
        "twitter": "https://twitter.com"
      }
    },
    {
      "name": "Fraser",
      "type": "Author",
      "age": 17,
      "social": {
        "facebook": "https://facebook.com",
        "twitter": "https://twitter.com"
      }
    }
  ]
}

main.go
读文件
定义 type struct
序列化/反序列化

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "os"
    "strconv"
)

// Users struct which contains
// an array of users
type Users struct {
    Users []User `json:"users"`
}

// User struct which contains a name
// a type and a list of social links
type User struct {
    Name   string `json:"name"`
    Type   string `json:"type"`
    Age    int    `json:"Age"`
    Social Social `json:"social"`
}

// Social struct which contains a
// list of links
type Social struct {
    Facebook string `json:"facebook"`
    Twitter  string `json:"twitter"`
}

func main() {
    // Open our jsonFile
    jsonFile, err := os.Open("users.json")
    // if we os.Open returns an error then handle it
    if err != nil {
        fmt.Println(err)
    }

    fmt.Println("Successfully Opened users.json")
    // defer the closing of our jsonFile so that we can parse it later on
    defer jsonFile.Close()

    // read our opened xmlFile as a byte array.
    byteValue, _ := ioutil.ReadAll(jsonFile)

    // we initialize our Users array
    var users Users

    // we unmarshal our byteArray which contains our
    // jsonFile's content into 'users' which we defined above
    json.Unmarshal(byteValue, &users)

    // we iterate through every user within our users array and
    // print out the user Type, their name, and their facebook url
    // as just an example
    for i := 0; i < len(users.Users); i++ {
        fmt.Println("User Type: " + users.Users[i].Type)
        fmt.Println("User Age: " + strconv.Itoa(users.Users[i].Age))
        fmt.Println("User Name: " + users.Users[i].Name)
        fmt.Println("Facebook Url: " + users.Users[i].Social.Facebook)
    }

}

JSON 是什么

GO语言里的JSON支持

序列化/反序列化

代码

实例: 读取一个 json 文件

参考