Marshalling and Unmarshalling in Golang

In this tutorial, we will explain how to encode and decode data in Golang. Data encoding is an important part of any programming language to encode data into JSON or decode data into String.

In Golang, struct data is converted into JSON and JSON data to string with Marshal() and Unmarshal() method. The methods returned data in byte format and we need to change returned data into JSON or String.

In our previous tutorial, we have explained about Parsing JSON Data in Golang. In this tutorial, we will explain about data marshal and unmarshal in Golang.

Also, read:

How to Make HTTP Requests in Golang

We will cover this tutorial step by step to know about marshal and unmarshal in Golang and convert struct data into JSON format and convert back JSON data to string with exemple.

What is Marshalling in Golang

Converting Go objects into JSON is called marshalling in Golang. As the JSON is a language-independent data format, the Golang has inbuilt encoding/json package to perform json related operations.

The encoding/json package has json.Marshal() method. This method takes object as parameter and returned byte code.

In below example, we have Employee struct defined.

type Employee struct {
	Name  string
	Age	int	
	Address string
}

As we will convert an instance of Employee struct into JSON, so we will use encoding/json Golang package to use json.Marshal() method to convert data.

import (
	"encoding/json"	
)

Now we will create object of Employee struct and pass with data and convert Struct Object into Byte data. The we will convert Byte data into JSON string to display data.

emp := Employee{Name: "George Smith", Age: 30, Address: "Newyork, USA"}
empData, err := json.Marshal(emp)
fmt.Println(string(empData))

Here is complete program to Marshal Employee struct into JSON.

package main

import (
	"encoding/json"
	"fmt"
)

type Employee struct {
	Name  string
	Age	int	
	Address string
}

func main() {
	emp := Employee{Name: "George Smith", Age: 30, Address: "Newyork, USA"}
	empData, err := json.Marshal(emp)
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(string(empData))
}

Now, when we run above program, we should see the following JSON output:

{"Name":"George Smith","Age":30,"Address":"Newyork, USA"}

What is Unmarshalling in Golang

Unmarshalling just opposite of Marshalling. The Golang encoding/json package has json.Unmarshal() method that used to convert json(Byte data) into Struct. As we have covered Marshalling of struct into JSON, now we will take that JSON string and Unmarshal that JSON into a Struct.

Here in this example, we have employee JSON string.

empJsonData := `{"Name":"George Smith","Age":30,"Address":"Newyork, USA"}

We will create Response Struct that we will use to match byte code after Unmarshal to display data.

type Response struct {
    Name string `json:"name"`
    Age int `json:"age"`
    Address string `json:"address"`
}

Now we will create JSON string into byte code. The we will Unmarshal byte code using json.Unmarshal() method and assign into response variable to display data.

	empJsonData := `{"Name":"George Smith","Age":30,"Address":"Newyork, USA"}`	
	empBytes := []byte(empJsonData)
	var resp Response
	json.Unmarshal(empBytes, &resp)
	fmt.Println(resp.Name)
	fmt.Println(resp.Age)
	fmt.Println(resp.Address)

Here is complete program to Unmarshal JSON byte code.

package main

import (
	"encoding/json"
	"fmt"
)

type Response struct {
    Name string `json:"name"`
    Age int `json:"age"`
    Address string `json:"address"`
}

func main() {		
	empJsonData := `{"Name":"George Smith","Age":30,"Address":"Newyork, USA"}`	
	empBytes := []byte(empJsonData)
	var emp Response
	json.Unmarshal(empBytes, &emp)
	fmt.Println(emp.Name)
	fmt.Println(emp.Age)
	fmt.Println(emp.Address)
}

Now, when we run above program, we should see the following output:

George Smith
30
Newyork, USA

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