generate-a-qr-code.md

Generate A QR Code

Category: Spring

You can generate a QR Code in Spring Boot using the Zebra Crossing (ZXing) library and a simple RestController.

Gradle dependencies

Add the following dependencies to your build.gradle file:

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-web'
	implementation 'com.google.zxing:core:3.4.1'
	implementation 'com.google.zxing:javase:3.4.1'
	testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

Buffered image converter

Create a HttpMessageConverter which converts a response object in the controller endpoint to a BufferedImage.

package com.orbiks.qrcode;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.BufferedImageHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;

import java.awt.image.BufferedImage;

@Configuration
public class BufferedImageConverter {

    @Bean
    public HttpMessageConverter<BufferedImage> httpMessageConverter() {
        return new BufferedImageHttpMessageConverter();
    }

}

Controller endpoint

Create a controller with an endpoint which accepts params for the text and size of the QR code. In this example, if the size query string parameter isn't supplied, it will default to 200 x 200 pixels.

The method should return a PNG.

package com.orbiks.qrcode.controllers;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.awt.image.BufferedImage;
import java.util.Optional;

@RestController
@RequestMapping(path = "/api/v1")
public class QrCodeGeneratorController {

    @GetMapping(path = "/qrcode", produces = MediaType.IMAGE_PNG_VALUE)
    public BufferedImage generateQRCodeImage(@RequestParam Optional<Integer> size, @RequestParam String text) throws Exception {
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        BitMatrix bitMatrix = qrCodeWriter.encode(text, BarcodeFormat.QR_CODE, size.orElse(200), size.orElse(200));
        return MatrixToImageWriter.toBufferedImage(bitMatrix);
    }

}

Go to the controller endpoint using a browser or Postman, specifying the value of the text query string parameter to embed in the QR code.

http://localhost:8080/api/v1/qrcode?size=250&text=https://www.porsche.com