Parsing JSON Data using Golang

JSON (Javascript Object Notation) is a standard format for storing data. The JSON format is the most used format in web applications to read and write dynamic data. Most of RESTful APIs are implemented to return JSON data response.

As in our previous tutorial you have learned how to Read File Line by Line using Golang. Here in this tutorial we are going to explain how to parse JSON data using Golang to implement in your web applications.

We will cover this tutorial step by step to create a JSON data file and read JSON file data. The we handle functionality to parse JSON.

Also, read:

Regular Expressions in Golang

Step1: Create JSON Data File

First we will create a simple JSON file employee.json using below JSON data to read the file and then parse it.

{
  "employee": [
    {
      "name": "Smith",
      "gender": "Male",
      "age": 40      
    },
    {
      "name": "Rosy",
      "gender": "Female",
      "age": 30      
    }
  ]
}

Step2: Read JSON Data File

To open JSON file, we will use os package. After opening the file, we handle JSON data parsing and close the file at the end of function.

jsonFile, err := os.Open("employee.json")
if err != nil {
    fmt.Println(err)
}
fmt.Println("Successfully Opened json file")
defer jsonFile.Close()

Step3: Parse JSON Data with Structs

Now we will parse the employee JSON data with by defining structs. Then we will unmarshal the JSON data using a set of predefined structs.

package main

import (
   "encoding/json"
)

type Employees struct {
    Employees []Employee `json:"employee"`
}

type Employee struct {
    Name   string `json:"name"`
    Gender string `json:"gender"`
    Age    int    `json:"Age"`

}

Step4: Unmarshalling JSON Data

After opening and reading the employee.json file, we will convert file to byte array using ioutil.ReadAll() method. Then we will pass byte array to json.Unmarshal() method to unmarshall json data.

func main() {    
    jsonFile, err := os.Open("employee.json")
    if err != nil {
        fmt.Println(err)
    }
	
    fmt.Println("Successfully Opened json file")
    defer jsonFile.Close()

    byteEmpValue, _ := ioutil.ReadAll(jsonFile)

    var employees Employees
    
    json.Unmarshal(byteEmpValue, &employees)

    
    for i := 0; i < len(employees.Employees); i++ {
        fmt.Println("Employee Name: " + employees.Employees[i].Name)
        fmt.Println("Employee Gender: " + employees.Employees[i].Gender)
        fmt.Println("Employee Age: " + strconv.Itoa(employees.Employees[i].Age))
    }

}

Step5: Complete Code to Parse JSON Data with Go

Here is the complete code main.go file to parse JSON data using Golang.

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "os"
    "strconv"
)

type Employees struct {
    Employees []Employee `json:"employee"`
}

type Employee struct {
    Name   string `json:"name"`
    Gender string `json:"gender"`
    Age    int    `json:"Age"`

}

func main() {    
    jsonFile, err := os.Open("employee.json")
    if err != nil {
        fmt.Println(err)
    }
	
    fmt.Println("Successfully Opened json file")
    defer jsonFile.Close()

    byteEmpValue, _ := ioutil.ReadAll(jsonFile)

    var employees Employees
    
    json.Unmarshal(byteEmpValue, &employees)

    
    for i := 0; i < len(employees.Employees); i++ {
        fmt.Println("Employee Name: " + employees.Employees[i].Name)
        fmt.Println("Employee Gender: " + employees.Employees[i].Gender)
        fmt.Println("Employee Age: " + strconv.Itoa(employees.Employees[i].Age))
    }

}

Conclusion

Hopefully this tutorial helped you to handle JSON data file parsing in Golang. If you find this tutorial helpful then please let us know in the comments section below.

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