Go JSON
Golang has built-in support for JSON (JavaScript Object Notation) through the encoding/json package. The package provides functions for encoding and decoding JSON data and handling errors that may occur during the process.
To encode a Go struct as JSON, you can use the json.Marshal() function, and to decode JSON data into a Go struct, you can use the json.Unmarshal() function.
Encoding JSON in Go:
This example uses the json.Marshal() function to convert a struct to a JSON-encoded byte slice. The json.Marshal() function takes an interface{} as an argument, so you can pass it any value that you want to encode as JSON.
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
}
func main() {
p := Person{Name: "John", Age: 30}
b, err := json.Marshal(p)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(string(b))
}Output
{"Name":"John","Age":30}Decoding JSON in Go:
This example uses the json.Unmarshal() function to convert a JSON-encoded byte slice to a struct. The json.Unmarshal() function takes a byte slice and a pointer to a struct as arguments.
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string
Age int
}
func main() {
b := []byte(`{"Name":"John","Age":30}`)
var p Person
err := json.Unmarshal(b, &p)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(p)
}Output
{John 30}Reading JSON from a file:
This example uses the ioutil.ReadFile() function to read the contents of a file into a byte slice. It then uses the json.Unmarshal() function to convert the byte slice to a struct.
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
)
type Person struct {
Name string
Age int
}
func main() {
b, err := ioutil.ReadFile("person.json")
if err != nil {
fmt.Println(err)
return
}
var p Person
err = json.Unmarshal(b, &p)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(p)
}Output
{John 30}Writing JSON to a file:
This example uses the json.Marshal() function to convert a struct to a JSON-encoded byte slice. It then uses the ioutil.WriteFile() function to write the contents into a file.
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
)
type Person struct {
Name string
Age int
}
func main() {
p := Person{Name: "John", Age: 30}
b, err := json.Marshal(p)
if err != nil {
fmt.Println(err)
return
}
err = ioutil.WriteFile("person.json", b, 0644)
if err != nil {
fmt.Println(err)
return
}
}Reading the JSON from the HTTP
This example uses the http.Get() function to make a GET request to a specified URL. The response from the server is stored in the resp variable. It then uses the ioutil.ReadAll() function to read the entire contents of the response body into a byte slice. It then uses the json.Unmarshal() function to convert the byte slice to a struct.
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
)
type Person struct {
Name string
Age int
}
func main() {
resp, err := http.Get("https://example.com/person.json")
if err != nil {
fmt.Println(err)
return
}
defer resp.Body.Close()
b, err := ioutil.ReadAll(resp.Body)
if err != nil {
fmt.Println(err)
return
}
var p Person
err = json.Unmarshal(b, &p)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(p)
}Output
{John 30}Conclusion
In conclusion, Go provides built-in support for encoding and decoding JSON through the encoding/json package. The json.Marshal() function encodes a struct or other value as a JSON-encoded byte slice, while the json.Unmarshal() function is used to decode a JSON-encoded byte slice into a struct or other value.
Additionally, You can read and write JSON data from and to a file using the io/ioutil package's ioutil.ReadFile() and ioutil.WriteFile() functions. And also, you can read a JSON from an HTTP response using net/http package's http.Get() function and ioutil.ReadAll().