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Golang JSON Marshal(encode) and Unmarshal(decode/parse) with examples

Rajeev Singh1 mins

Golang JSON Marshal(encode) and Unmarshal(decode/parse) with examples

JSON (Javascript Object Notation) is a simple data interchange format widely used in http communication.

Go has built-in support for encoding and decoding JSON data. In this article, you’ll learn how to convert a Go type (native or struct) to JSON and vice versa. We’ll use the following structs in this article for demonstrating JSON encoding and decoding in Go -

type User struct {
	Id         int
	Name       string            `json:"name"`
	Email      string            `json:"email"`
	Password   string            `json:"-"`
	Hobbies    []string          `json:"hobbies,omitempty"`
	Address    Address           `json:"address"`
	Attributes map[string]string `json:"attributes"`
}

type Address struct {
	City    string `json:"city"`
	State   string `json:"state"`
	Country string `json:"country"`
}

JSON Encoding (Marshaling): Convert GO types to JSON

You can use the Marshal() function to marshal or serialize a Go type to JSON data:

func Marshal(v interface{}) ([]byte, error)

Following is an example -

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	user := User{
		Id:       1,
		Name:     "Rajeev Singh",
		Email:    "rajeevhub@gmail.com",
		Password: "123456",
		Hobbies:  []string{"Coding", "Travelling", "Photography"},
		Address: Address{
			City:    "Bangalore",
			State:   "Karnataka",
			Country: "India",
		},
		Attributes: map[string]string{
			"Twitter":   "callicoder",
			"Instagram": "rajeevhub",
		},
	}

	jsonData, err := json.Marshal(user)
	if err != nil {
		fmt.Println(err)
		return
  }
  
	fmt.Println(string(jsonData))
}
# Output
{"Id":1,"name":"Rajeev Singh","email":"rajeevhub@gmail.com","hobbies":["Coding","Travelling","Photography"],"address":{"city":"Bangalore","state":"Karnataka","country":"India"},"attributes":{"Instagram":"rajeevhub","Twitter":"callicoder"}}

JSON Decoding (Unmarshaling or Parsing): Convert JSON to Go type

To parse or deserialize a JSON string to a Go type, you can use the Unmarshal() function:

func Unmarshal(data []byte, v interface{}) error

Here is an example of how to use the Unmarshal() function:

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
  jsonData := `
  {
   "Id": 1,
   "name": "Rajeev Singh",
   "email": "rajeevhub@gmail.com",
   "password": "123456",
   "hobbies": [
      "Coding",
      "Travelling",
      "Photography"
   ],
   "address": {
      "city": "Bangalore",
      "state": "Karnataka",
      "country": "India"
   },
   "attributes": {
      "Instagram": "rajeevhub",
      "Twitter": "callicoder"
   }
  }
  `

  var user User
  err := json.Unmarshal([]byte(jsonData), &user)
  if err != nil {
    fmt.Println(err)
    return
  }
  
  fmt.Println(user)
}
# Output
{1 Rajeev Singh rajeevhub@gmail.com  [Coding Travelling Photography] {Bangalore Karnataka India} map[Instagram:rajeevhub Twitter:callicoder]}