Json to Struct and Struct to Json in Golang

In this post we will see the conversion between struct and json#

If you are building any api or anything there might be scenario where you had to convert json data into predefined struct or reverse of that, so we will see how you can do that

Golang’s default library have lots of things done already for our simplicity. Its default library is huge almost for every scenario you will get the default package. go support lots of conversion mechanism like xml json. these conversion comes under encoding package.

• json.Marshal() this will convert struct to json
• json.Unmarshal() this will convert json to struct

for converting struct into json we have to user json tag at struct level to specify the json key name otherwise it will take the name of struct field.

for example:

type User struct {
		Username  string `json:"username"`
		Firstname string `json:"first_name"`
		Lastname  string `json:"last_name"`
		Email     string `json:"email"`
	}

json tag is very important for Marshaling and Unmarshaling both

fields of struct must be exported means it should be first letter uppercase otherwise Marshal function wont be able to read those fields.

Please see the whole code to understand how we can use. it is very easy

package main

import (
	"encoding/json"
	"fmt"
)

func main() {

	type User struct {
		Username  string `json:"username"`
		Firstname string `json:"first_name"`
		Lastname  string `json:"last_name"`
		Email     string `json:"email"`
	}

	user := &User{
		Username:  "devjohn",
		Firstname: "John",
		Lastname:  "Cena",
		Email:     "abc@gmail.com",
	}
	jsonData, err := json.Marshal(user)
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(string(jsonData))

	userArr := []User{
		*user,
		*user,
	}

	jsonArrData, err := json.Marshal(userArr)
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(string(jsonArrData))

	// decoding json into struct

	jsonString := "[{\"username\":\"devjohn\",\"first_name\":\"John\",\"last_name\":\"Cena\",\"email\":\"abc@gmail.com\"}]"

	var userStruct []User

	err = json.Unmarshal([]byte(jsonString), &userStruct)
	if err != nil {
		panic(err)
	}
	fmt.Println(userStruct)
}

For xml conversion there is package encoding/xml. i will write a post on that also.