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    Java QR Code Generator

    Today we will look into the Java QR code generator program. If you are tech and gadget savvy, then you must be aware of the QR code. You will find it everywhere these days – in blogs, websites, and even in some public places. This is very popular in mobile apps, where you scan the QR code using a QR Code scanner app and it will show you the text or redirect you to the web page if it’s URL. I came across this recently and found it very interesting. If you want to know about QR Code, you can find a lot of useful information at Wikipedia QR Code Page.

    Java QR code generator

    When I found QR code images on so many websites, I started looking for java QR code generator. I looked into some open source APIs and found zxing to be the simple and best to use. If you want to generate a QR code image, then we only need its core library. Just add below dependency to your maven project.

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    <dependency>
	<groupId>com.google.zxing</groupId>
	<artifactId>core</artifactId>
	<version>3.3.2</version>
</dependency>

    If you want to read QR image through the command line, then we need to use it’s JavaSE library. You can add below dependency for it.

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    <dependency>
	<groupId>com.google.zxing</groupId>
	<artifactId>javase</artifactId>
	<version>3.3.2</version>
</dependency>

    This will also let you know two extra dependencies required to run from the command line. We will have to add these jars into classpath to run the client app to read the QR code image. We will see this in action later on in this tutorial.

    zxing example to generate QR code image

    Here is the program you can use to create QR Code image with zxing API. GenerateQRCode.java

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    package com.journaldev.qrcode.generator;

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Hashtable;

import javax.imageio.ImageIO;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.WriterException;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class GenerateQRCode {

	public static void main(String[] args) throws WriterException, IOException {
		String qrCodeText = "https://www.journaldev.com";
		String filePath = "JD.png";
		int size = 125;
		String fileType = "png";
		File qrFile = new File(filePath);
		createQRImage(qrFile, qrCodeText, size, fileType);
		System.out.println("DONE");
	}

	private static void createQRImage(File qrFile, String qrCodeText, int size, String fileType)
			throws WriterException, IOException {
		// Create the ByteMatrix for the QR-Code that encodes the given String
		Hashtable<EncodeHintType, ErrorCorrectionLevel> hintMap = new Hashtable<>();
		hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
		QRCodeWriter qrCodeWriter = new QRCodeWriter();
		BitMatrix byteMatrix = qrCodeWriter.encode(qrCodeText, BarcodeFormat.QR_CODE, size, size, hintMap);
		// Make the BufferedImage that are to hold the QRCode
		int matrixWidth = byteMatrix.getWidth();
		BufferedImage image = new BufferedImage(matrixWidth, matrixWidth, BufferedImage.TYPE_INT_RGB);
		image.createGraphics();

		Graphics2D graphics = (Graphics2D) image.getGraphics();
		graphics.setColor(Color.WHITE);
		graphics.fillRect(0, 0, matrixWidth, matrixWidth);
		// Paint and save the image using the ByteMatrix
		graphics.setColor(Color.BLACK);

		for (int i = 0; i < matrixWidth; i++) {
			for (int j = 0; j < matrixWidth; j++) {
				if (byteMatrix.get(i, j)) {
					graphics.fillRect(i, j, 1, 1);
				}
			}
		}
		ImageIO.write(image, fileType, qrFile);
	}

}

    zxing example to read QR code

    If you don’t have a mobile app to test it, don’t worry. You can read QR code with zxing API through the command line. Below is the command to read the QR code image file. Notice the additional jars in the classpath that zxing depends on.

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    $java -cp $HOME/.m2/repository/com/google/zxing/javase/3.3.2/javase-3.3.2.jar:.:$HOME/.m2/repository/com/google/zxing/core/3.3.2/core-3.3.2.jar:$HOME/.m2/repository/com/beust/jcommander/1.72/jcommander-1.72.jar:$HOME/.m2/repository/com/github/jai-imageio/jai-imageio-core/1.3.1/jai-imageio-core-1.3.1.jar com.google.zxing.client.j2se.CommandLineRunner JD.png

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