Generating QR Codes in Java with QRGen and ZXing

QR codes have become ubiquitous due to smartphones, and this article introduces QR codes and demonstrates how to generate them in Java.

It explains the history of QR codes, then introduces the open‑source ZXing library and the QRGen wrapper that simplifies QR code creation.

After downloading the required JAR files, the article provides a complete Java “Hello World” example that creates a PNG image and writes it to C:\QR_Code.JPG .

package net.viralpatel.qrcode;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import net.glxn.qrgen.QRCode;
import net.glxn.qrgen.image.ImageType;

public class Main {
    public static void main(String[] args) {
        ByteArrayOutputStream out = QRCode.from("Hello World").to(ImageType.PNG).stream();
        try {
            FileOutputStream fout = new FileOutputStream(new File("C:QR_Code.JPG"));
            fout.write(out.toByteArray());
            fout.flush();
            fout.close();
        } catch (FileNotFoundException e) {
            // Do Logging
        } catch (IOException e) {
            // Do Logging
        }
    }
}

The code uses QRCode.from(...).to(ImageType.PNG).stream() and standard Java I/O to save the image.

Additional examples show how to generate QR codes for URLs, customize image type and size, and produce QR code files directly.

// get QR file from text using defaults
File file = QRCode.from("Hello World").file();
// get QR stream from text using defaults
ByteArrayOutputStream stream = QRCode.from("Hello World").stream();
// override the image type to be JPG
QRCode.from("Hello World").to(ImageType.JPG).file();
QRCode.from("Hello World").to(ImageType.JPG).stream();
// override image size to be 250x250
QRCode.from("Hello World").withSize(250, 250).file();
QRCode.from("Hello World").withSize(250, 250).stream();
// override size and image type
QRCode.from("Hello World").to(ImageType.GIF).withSize(250, 250).file();
QRCode.from("Hello World").to(ImageType.GIF).withSize(250, 250).stream();

A servlet example demonstrates dynamic QR code generation: an HTML form posts text to a QRCodeServlet , which reads the parameter, creates a PNG stream, and writes it to the HTTP response.

package net.viralpatel.qrcodes;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.glxn.qrgen.QRCode;
import net.glxn.qrgen.image.ImageType;

public class QRCodeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String qrtext = request.getParameter("qrtext");
        ByteArrayOutputStream out = QRCode.from(qrtext).to(ImageType.PNG).stream();
        response.setContentType("image/png");
        response.setContentLength(out.size());
        OutputStream outStream = response.getOutputStream();
        outStream.write(out.toByteArray());
        outStream.flush();
        outStream.close();
    }
}

The required web.xml configuration for mapping the servlet is also provided.

<!--?xml version="1.0" encoding="UTF-8"?-->
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
    <display-name>QR_Code_Servlet</display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>QRCodeServlet</servlet-name>
        <servlet-class>net.viralpatel.qrcodes.QRCodeServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>QRCodeServlet</servlet-name>
        <url-pattern>/qrservlet</url-pattern>
    </servlet-mapping>
</web-app>

The tutorial concludes that generating QR codes in Java is straightforward and can be easily integrated into existing applications.