An article explaining golang's json operation in detail

##golang’s json operation

lightweight data exchange format. Easy to read and write. golang provides the encoding/json package to operate JSON data.

1. Convert structure to JSON

(1) Use the json.Marshal() method to convert the structure into a JSON string

import (
	"encoding/json"
	"fmt")type Student struct {
	Name string
	Age int
	Skill string}func main()  {
	stu := Student{"tom", 12, "football"}
	data, err := json.Marshal(&stu)
	if err != nil {
		fmt.Printf("序列化错误 err=%v\n", err)
		return
	}
	fmt.Println("序列化后: ", string(data))}

(2) JSON To convert a string into a structure, you can use the json.Unmarshal() method

func main()  {
	str := `{"Name":"tom","Age":12,"Skill":"football"}`
	var stu2 Student
	err := json.Unmarshal([]byte(str), &stu2)
	if err != nil {
		fmt.Printf("反序列化错误 err=%v\n", err)
		return
	}
	fmt.Printf("反序列化后: Student=%v, Name=%v\n", stu2, stu2.Name)}

to print: After deserialization: Student={tom 12 football} , Name=tom

(3) How to realize that the name of the key can be customized after the structure is serialized

tag label

type Student struct {
	Name string   `json:"stu_name"`
	Age int       `json:"stu_age"`
	Skill string  // 也可以不指定 tag标签，默认就是 变量名称}func main()  {
	stu := Student{"tom", 12, "football"}
	data, err := json.Marshal(&stu)
	if err != nil {
		fmt.Printf("序列化错误 err=%v\n", err)
		return
	}
	fmt.Println("序列化后: ", string(data))}

After serialization: {"stu_name":"tom ","stu_age":12,"Skill":"football"}

2. Convert map to JSON

func main()  {
	// map 转 Json字符串
	m := make(map[string]interface{})
	m["name"] = "jetty"
	m["age"] = 16

	data, err := json.Marshal(&m)
	if err != nil {
		fmt.Printf("序列化错误 err=%v\n", err)
		return
	}
	fmt.Println("序列化后: ", string(data))    // 打印: 序列化后:  {"age":16,"name":"jetty"}

	// Json字符串 转 map
	str := `{"age":25,"name":"car"}`
	err = json.Unmarshal([]byte(str), &m)
	if err != nil {
		fmt.Printf("反序列化错误 err=%v\n", err)
		return
	}
	fmt.Printf("反序列化后: map=%v, name=%v\n", m, m["name"])
	// 打印: 反序列化后: map=map[age:25 name:car], name=car}

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3. Can the variables of the structure be converted into json data without tags?

If the first letter of the variable is lowercase, it is private. Because the reflection information cannot be obtained, it cannot be transferred.
• If the first letter of the variable is capitalized, it is public. It can be converted normally regardless of whether tags are added or not. Variables with tags will be displayed according to the name of the tag.

type User struct {
	Name string    `json:"u_name"`
	age int        `json:"u_age"`
	Skill string   // 也可以不指定 tag标签，默认就是 变量名称
	addr string}func main()  {
	user := User{"admin", 23, "football", "上海"}
	data, err := json.Marshal(&user)
	if err != nil {
		fmt.Printf("序列化错误 err=%v\n", err)
		return
	}
	fmt.Println("序列化后: ", string(data))  // 打印: 序列化后:  {"u_name":"admin","Skill":"football"}}

If the first letter is lowercase, it cannot be converted to json data regardless of whether it is added with a tag, while if it is uppercase, it can be aliased with a tag, and if it is not added with a tag, it will be converted into json data. The fields are consistent with the original names of the structure variables

4. Some tips for JSON operations

(1) Ignore the specified fields of the struct

type User struct {
	Name string    `json:"u_name"`
	Password string `json:"password"`
	Email string `json:"email"`}func main()  {
	user := User{"admin", "pwd", "user@163.com"}
	person := Person{23, "上海"}
	// 忽略掉 Password 字段
	data, _ := json.Marshal(struct {
		*User
		Password string `json:"password,omitempty"`
	}{User: &user})
	fmt.Println("忽略字段: ", string(data))  // 打印: 忽略字段: {"u_name":"admin","email":"user@163.com"}}

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(2) Add additional Field

data, _ = json.Marshal(struct {
	*User
	Skill string `json:"skill"`  // 临时添加额外的 Skill字段}{
	User: &user,
	Skill: "football",})fmt.Println("添加额外字段: ", string(data))

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(3) Merge two structs

type User struct {
	Name string    `json:"u_name"`
	Password string `json:"password"`
	Email string `json:"email"`}type Person struct {
	Age int
	Addr string `json:"addr"`}func main()  {
    // 初始化两个 struct
	user := User{"admin", "pwd", "user@163.com"}
	person := Person{23, "上海"}
	
	data, _ := json.Marshal(struct {
		*User		*Person	}{
		User: &user,
		Person: &person,
	})
	
	fmt.Println("合并两个struct: ", string(data))}

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(4) The string is passed to the int type

emp := struct {                    // 创建匿名 struct
	Num int `json:"num,string"`}{15,}data, _ := json.Marshal(&emp)fmt.Println("数字转成字符串: ", string(data))       // 数字转成字符串: {"num":"15"}str := `{"Num":"25"}`_ = json.Unmarshal([]byte(str), &emp)fmt.Printf("字符串转成数字: Emp.Num=%v\n", emp.Num) // 字符串转成数字: Emp.Num=25

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(5) A json is divided into two structs

str = ` {"u_name":"system","password":"abc","email":"user2@163.com","Age":23,"addr":"杭州"}`var user2 Uservar person2 Person_ := json.Unmarshal([]byte(str), &struct {
	*User	*Person}{
	User: &user2,
	Person: &person2,})fmt.Printf("分成两个struct: User=%v, Person=%v\n", user2, person2)

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