Web Application to generate QR code in Golang

The basic example of web application to generate bar-code. The algorithm or internal logic to generate bar-code is available in third-party bar-code package. Here the goal is to show an example how to use a package and create a web-application.

1. Install required package

The Barcode package can be used to create different types of bar-codes. You can install this package by executing the following command in your git bash terminal:

go get github.com/boombuler/barcode

2. Development

2.1 Source code of main.go

The main function begins with a call to http.HandleFunc, which tells the http package to handle all requests to the web root ("/") with homeHandler. The function homeHandler is of the type http.HandlerFunc. It takes an http.ResponseWriter and an http.Request as its arguments.

The function viewCodeHandler that will allow users to view a generated QR-code in new page. It will handle URLs prefixed with "/generator/". The function template.ParseFiles will read the contents of generator.html and return a *template.Template.

package main

import (
	"image/png"
	"net/http"
	"text/template"

	"github.com/boombuler/barcode"
	"github.com/boombuler/barcode/qr"
)

type Page struct {
	Title string
}

func main() {
	http.HandleFunc("/", homeHandler)
	http.HandleFunc("/generator/", viewCodeHandler)
	http.ListenAndServe(":8080", nil)
}

func homeHandler(w http.ResponseWriter, r *http.Request) {
	p := Page{Title: "QR Code Generator"}

	t, _ := template.ParseFiles("generator.html")
	t.Execute(w, p)
}

func viewCodeHandler(w http.ResponseWriter, r *http.Request) {
	dataString := r.FormValue("dataString")

	qrCode, _ := qr.Encode(dataString, qr.L, qr.Auto)
	qrCode, _ = barcode.Scale(qrCode, 512, 512)

	png.Encode(w, qrCode)
}

The FormValue function will gives the value of dataString input field which will be used to generate the QR code using Encode function.

2.2 Source code of generator.html.

A template file containing the HTML form.

<h1>{{.Title}}</h1>
<div>Please enter the string you want to QRCode.</div>
<form action="generator/" method=post>
    <input type="text" name="dataString">
    <input type="submit" value="Submit">
</form>

3. Execution

Using command line or putty run command "go run main.go"

You will see an output like the image below.