In this tutorial, we will learn how to use JSON in Golang with examples.
JSON (JavaScript Object Notation) is a lightweight data interchange format.
In Golang, the encoding/json package implements the encoding and decoding of JSON.
Table of contents:
Go - Convert Struct to JSON
In the example, we transform a Go struct into JSON format:
package main
import (
"encoding/json"
"fmt"
"log"
)
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
func main() {
e1 := Employee{1, "John", "Cena", "john@gmail.com"}
json_data, err := json.Marshal(e1)
if err != nil {
log.Fatal(err)
}
fmt.Println(string(json_data))
}
Output:
{"Id":1,"FirstName":"John","LastName":"Cena","Email":"john@gmail.com"}
We declare the Employee struct:
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
We create the struct instance:
e1 := Employee{1, "John", "Cena", "john@gmail.com"}
We encode the u1 struct into JSON with Marshal.
json_data, err := json.Marshal(e1)
Since json_data is a byte array, we convert it to a string with the string function:
fmt.Println(string(json_data))
Go - Convert an array/slice into a JSON
In the example, we transform a slice of structs into JSON format:
package main
import (
"encoding/json"
"fmt"
"log"
)
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
func main() {
employees := []Employee{
{Id: 2, FirstName: "Amir", LastName: "Khan", Email: "Amir@gmail.com"},
{Id: 3, FirstName: "Lucy", LastName: "Smith", Email: "Smith@gmail.com"},
{Id: 4, FirstName: "David", LastName: "Brown", Email: "David@gmail.com"},
}
json_data2, err := json.Marshal(employees)
if err != nil {
log.Fatal(err)
}
fmt.Println(string(json_data2))
}
Output:
[{"Id":2,"FirstName":"Amir","LastName":"Khan","Email":"Amir@gmail.com"},{"Id":3,"FirstName":"Lucy","LastName":"Smith","Email":"Smith@gmail.com"},{"Id":4,"FirstName":"David","LastName":"Brown","Email":"David@gmail.com"}]
The output can be pretty-printed with the MarshalIndent function.
package main
import (
"encoding/json"
"fmt"
"log"
)
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
func main() {
employees := []Employee{
{Id: 2, FirstName: "Amir", LastName: "Khan", Email: "Amir@gmail.com"},
{Id: 3, FirstName: "Lucy", LastName: "Smith", Email: "Smith@gmail.com"},
{Id: 4, FirstName: "David", LastName: "Brown", Email: "David@gmail.com"},
}
json_data2, err := json.MarshalIndent(employees, "", " ")
if err != nil {
log.Fatal(err)
}
fmt.Println(string(json_data2))
}
Output:
[ { "Id": 2, "FirstName": "Amir", "LastName": "Khan", "Email": "Amir@gmail.com" }, { "Id": 3, "FirstName": "Lucy", "LastName": "Smith", "Email": "Smith@gmail.com" }, { "Id": 4, "FirstName": "David", "LastName": "Brown", "Email": "David@gmail.com" } ]
Go - Convert JSON to Struct
In this source code example, we show how to convert JSON to Struct in Golang :
package main
import (
"encoding/json"
"fmt"
"log"
)
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
func main() {
var e1 Employee
data := []byte(`{"Id": 1, "FirstName": "John", "LastName": "Cena", "Email" : "john@gmail.com"}`)
err := json.Unmarshal(data, &e1)
if err != nil {
log.Fatal(err)
}
fmt.Println("Struct is:", e1)
fmt.Println("FirstName: ", e1.FirstName)
fmt.Println("LastName: ", e1.LastName)
fmt.Println("Email: ", e1.Email)
}
Output:
Struct is: {1 John Cena john@gmail.com} FirstName: John LastName: Cena Email: john@gmail.com
Go - Convert JSON to an array/slice
In this source code example, we show how to convert JSON to an array/slice in Golang with an example:
package main
import (
"encoding/json"
"fmt"
"log"
)
type Employee struct {
Id int
FirstName string
LastName string
Email string
}
func main() {
var employees []Employee
data2 := []byte(`
[
{"Id": 1, "FirstName": "Amir", "LastName": "Khan", "Email": "Amir@gmail.com"},
{"Id": 2, "FirstName": "Lucy", "LastName": "Smith", "Email": "Smith@gmail.com"},
{"Id": 3, "FirstName": "David", "LastName": "Brown", "Email": "David@gmail.com"}
]`)
err2 := json.Unmarshal(data2, &employees)
if err2 != nil {
log.Fatal(err2)
}
for i := range employees {
fmt.Println(employees[i])
}
}
Output:
{1 Amir Khan Amir@gmail.com} {2 Lucy Smith Smith@gmail.com} {3 David Brown David@gmail.com}
Golang Related Tutorials
- Go (Golang) Functions with Examples
- Go (Golang) Operators with Examples
- Go ( Golang) - Read Input from User or Console
- Go (Golang) Read and Write File Example Tutorial
- Go (Golang) Array Tutorial
- Go (Golang) Slices Tutorial with Examples
- Go (Golang) Maps Tutorial with Examples
- Go (Golang) Structs Tutorial with Examples
- Go (Golang) Struct JSON Tutorial
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