json包可以实现json的编码和解码，就是将json字符串转换为struct，或者将struct转换为json。
一 核心函数1.1 Marshal
func Marshal(v interface{}) ([]byte, error)
将struct编码成json，可以接收任意类型
map[string]T实例演示：
① 结构体转换为json
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
Email string
}
func main() {
p := Person{
Name: "Psych",
Age: 20,
Email: "Psych@mail.com",
}
b, _ := json.Marshal(p)
fmt.Printf("b: %v\n", string(b))
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
b: {"Name":"Psych","Age":20,"Email":"Psych@mail.com"}
[Done] exited with code=0 in 0.965 seconds
② 解析嵌套类型
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
Email string
Parent []string
}
func main() {
p := Person{
Name: "Psych",
Age: 20,
Email: "Psych@mail.com",
Parent: []string{"Daddy", "Mom"},
}
b, _ := json.Marshal(p)
fmt.Printf("b: %v\n", string(b))
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
b: {"Name":"Psych","Age":20,"Email":"Psych@mail.com","Parent":["Daddy","Mom"]}
[Done] exited with code=0 in 1.018 seconds
1.2 Unmarshal
func Unmarshal(data []byte, v interface{}) error
将json转码为struct结构体
这个函数会把传入的 data 作为一个JSON来进行解析，解析后的数据存储在参数 v 中。这个参数 v 也是任意类型的参数（但一定是一个类型的指针），原因是我们在是以此函数进行JSON 解析的时候，这个函数不知道这个传入参数的具体类型，所以它需要接收所有的类型。
实例演示：
① json转换为结构体
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
Email string
}
func main() {
b := []byte(`{"Name":"Psych","Age":20,"Email":"Psych@mail.com"}`)
var m Person
json.Unmarshal(b, &m)
fmt.Printf("m: %v\n", m)
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
m: {Psych 20 Psych@mail.com}
[Done] exited with code=0 in 1.045 seconds
② 解析嵌套类型
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
Email string
Parent []string
}
func main() {
b := []byte(`{"Name":"Psych","Age":20,"Email":"Psych@mail.com","Parents":["Daddy","Mon"]}`)
var m map[string]interface{}
json.Unmarshal(b, &m)
fmt.Printf("m: %v\n", m)
for k, v := range m {
fmt.Printf("k: %v v: %v\n", k, v)
}
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
m: map[Age:20 Email:Psych@mail.com Name:Psych Parents:[Daddy Mon]]
k: Name v: Psych
k: Age v: 20
k: Email v: Psych@mail.com
k: Parents v: [Daddy Mon]
[Done] exited with code=0 in 1.01 seconds
2.1 Decoder
type Decoder struct {
// contains filtered or unexported fields
}
从输入流读取并解析json，应用于io流Reader Writer可以扩展到http websocket等场景
实例演示：
package main
import (
"encoding/json"
"fmt"
"os"
)
func main() {
f, _ := os.Open("a.json")
defer f.Close()
d := json.NewDecoder(f)
var v map[string]interface{}
d.Decode(&v)
fmt.Printf("v: %v\n", v)
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
v: map[Age:20 Email:Psych@mail.com Name:Psych Parent:[Daddy Mom]]
[Done] exited with code=0 in 0.956 seconds
其中a.json文件内容为：
{"Name":"Psych","Age":20,"Email":"Psych@mail.com","Parent":["Daddy","Mom"]}
2.2 Encoder
type Encoder struct {
// contains filtered or unexported fields
}
写json到输出流，应用于io流Reader Writer可以扩展到http websocket等场景
实例演示①
package main
import (
"encoding/json"
"os"
)
type Person struct {
Name string
Age int
Email string
Parent []string
}
func main() {
p := Person{
Name: "Psych",
Age: 20,
Email: "Psych@mail.com",
Parent: []string{"Daddy", "Mom"},
}
f, _ := os.OpenFile("a.json", os.O_WRONLY, 077)
defer f.Close()
d := json.NewEncoder(f)
d.Encode(p)
}
运行之后的a.json为（原文件内容为空）：
{"Name":"Psych","Age":20,"Email":"Psych@mail.com","Parent":["Daddy","Mom"]}
实例演示②
package main
import (
"encoding/json"
"fmt"
"log"
"os"
)
func test() {
// dec := json.NewDecoder(os.Stdin)
f, _ := os.Open("a.json")
dec := json.NewDecoder(f)
enc := json.NewEncoder(os.Stdout)
for {
var v map[string]interface{}
if err := dec.Decode(&v); err != nil {
log.Println(err)
return
}
fmt.Printf("v: %v\n", v)
if err := enc.Encode(&v); err != nil {
log.Println(err)
}
}
}
func main() {
test()
}
运行结果：
[Running] go run "c:\Users\Mechrevo\Desktop\go_pro\test.go"
v: map[Age:20 Email:Psych@mail.com Name:Psych Parent:[Daddy Mom]]
{"Age":20,"Email":"Psych@mail.com","Name":"Psych","Parent":["Daddy","Mom"]}
2022/07/14 17:55:30 EOF
[Done] exited with code=0 in 1.016 seconds