This document discusses how to create QR codes in Java. It provides an overview of what QR codes are and how they can be used. It then outlines how to set up the ZXing library to generate and decode QR codes in Java code. It includes a full Java class example with methods to create QR codes from text or URLs and decode an image-based QR code. Finally, it lists some common Java tools and tutorials for additional learning.

1. Creating QR codes in Java
Alison McGreavy

2. What’s a QR code?
QR is short for “Quick
Response”.
Developed in Japan by Denso
Wave http://www.denso-
wave.com/qrcode/index-e.html
Is a 2D barcode.
Can hold
•URL
•VCard
•Text
•meCard
http://en.wikipedia.org/wiki/QR_code

3. How can I decode a QR code?
Use an app on your smartphone to scan in the QR code
Use an online tool to enter the
URL of an image or upload an
image

4. How can I create a QR code?
Use a smartphone app
Or an online tool such as
http://zxing.appspot.com/generator

5. Yes, but how can I create a QR code?
(preferably in Java)

6. ZXing
• Download the ZXing-2.0.zip files from http://code.google.com/p/zxing/
• Unzip this on your local machine i.e. C:/zxing-2.0
• Install the ‘core’ package C:/zxing-2.0/core
• Install the ‘javase’ package C:/zxing-2.0/javase

7. Java
• Java download – use JDK for development
http://www.oracle.com/technetwork/java/javase/downloads/index.html
• Set JAVA_HOME environment variable to location of JDK ie C:Program
FilesJavajdk1.6.0_32bin
• Add JAVA_HOME variable to PATH variable
• Create Java project
• Add code.jar and jse.jar to your project classpath
• Start to code

8. Java class to create & decode QR codes
package uk.co.girlgeek;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import javax.imageio.ImageIO;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.HybridBinarizer;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.LuminanceSource;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.Reader;
public class QRCreator {
private static String IMAGEDIR = "C:/Alison/images";
private static int IMAGE_WIDTH = 400;
private static int IMAGE_HEIGHT = 400;

9. Main method
public static void main(String[] args) {
try {
QRCreator qrTest = new QRCreator();
// Create a QR code from a text message
String filenameOfQrFromText = IMAGEDIR + "/qr_fromtext.png";
String messageToEncode = "Hi there my name is Alison and my email is almcgreavy@yahoo.co.uk";
qrTest.createQRCode(messageToEncode, filenameOfQrFromText);
// Create a QR code from a URL
String filenameofQrfromURL = IMAGEDIR + "/qr_fromurl.png";
String urlToEncode = "http://www.geekgirlmeetup.co.uk";
qrTest.createQRCode(urlToEncode, filenameofQrfromURL);
// Read a text QR code
qrTest.readQRCode(filenameOfQrFromText);
// Read a URL QR code
qrTest.readQRCode(filenameofQrfromURL);
} catch (Exception e) {
e.printStackTrace();
System.exit(-1);
}
}

10. Method to Create QR code
private void createQRCode(String message, String filename) throws Exception {
File file = new File(filename);
BitMatrix bitMatrix = new QRCodeWriter().encode(message, BarcodeFormat.QR_CODE, IMAGE_WIDTH,
IMAGE_HEIGHT);
MatrixToImageWriter.writeToStream(bitMatrix, "PNG", new FileOutputStream(file));
System.out.println("Creating QR Image: " + file.getAbsolutePath());
}

11. Method to Decode a QR code
private void readQRCode(String imageFilename) throws Exception {
InputStream barCodeInputStream = new FileInputStream(imageFilename);
BufferedImage barCodeBufferedImage = ImageIO.read(barCodeInputStream);
LuminanceSource source = new BufferedImageLuminanceSource(
barCodeBufferedImage);
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
Reader reader = new MultiFormatReader();
com.google.zxing.Result result = reader.decode(bitmap);
System.out.println("QR text is: " + result.getText());
}

12. Java Tools & Tutorials
IDE : Eclipse http://www.eclipse.org/
Build Tools : Ant / Maven http://maven.apache.org/
Version Control: CVS http://en.wikipedia.org/wiki/Concurrent_Versions_System
Continuous Integration: Jenkins http://en.wikipedia.org/wiki/Jenkins_(software)
Unit testing: Junit http://en.wikipedia.org/wiki/JUnit
Jmock http://www.jmock.org/
Quality Metrics: Checkstyle http://checkstyle.sourceforge.net/
PMD http://pmd.sourceforge.net/pmd-5.0.0/
Issue Management: Bugzilla http://www.bugzilla.org/about/
Java Tutorials : http://docs.oracle.com/javase/tutorial/
http://www.javaranch.com/
http://www.coderanch.com/how-to/java/how-to-create-java-program

13. Alison McGreavy almcgreavy@yahoo.co.uk