Java QR Code Generator

Generating QR codes in Java is straightforward using a reliable library. This article shows a concise, practical method using ZXing (Zebra Crossing) to create PNG QR codes from text or URLs, plus options for size, error correction, and custom colors.

What you’ll need

Java 8+ (JDK)
Maven or Gradle (or add ZXing jars manually)
ZXing core and javase modules

Maven dependencies:

xml
<dependency>
<groupId>com.google.zxing</groupId>
  <artifactId>core</artifactId>
  <version>3.5.1</version>
</dependency>
<dependency>
  <groupId>com.google.zxing</groupId>
  <artifactId>javase</artifactId>
  <version>3.5.1</version>
</dependency>

Simple QR code generator (PNG)

This example creates a PNG file from input text, with configurable size and error correction.

java
import com.google.zxing.*;
import com.google.zxing.client.j2se.MatrixToImageConfig;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;

public class QRCodeGenerator {
    public static void generate(String text, int size, String filePath) throws Exception {
        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, “UTF-8”);
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M); // L, M, Q, H
        hints.put(EncodeHintType.MARGIN, 1);

        BitMatrix bitMatrix = new MultiFormatWriter().encode(
                text,
                BarcodeFormat.QR_CODE,
                size,
                size,
                hints         );

        // Optional: custom colors (foreground, background)
        int foreground = 0xFF000000; // black
        int background = 0xFFFFFFFF; // white
        MatrixToImageConfig config = new MatrixToImageConfig(foreground, background);

        Path path = Paths.get(filePath);
        MatrixToImageWriter.writeToPath(bitMatrix, “PNG”, path, config);
    }

    public static void main(String[] args) throws Exception {
        String text = “https://example.com”;
        int size = 300;
        String filePath = “qrcode.png”;
        generate(text, size, filePath);
        System.out.println(“QR code generated: “ + filePath);
    }
}

Customization options

Size: change the width/height (e.g., 150–1000 px).
Error correction: L (7%), M (15%), Q (25%), H (30%) — higher gives more resiliency but larger modules.
Margin: white border in modules; default often 4; reduce for denser images.
Colors: set foreground/background in MatrixToImageConfig.
Encoding: use UTF-8 for non-ASCII text.

Embedding logos

To add a small logo at center:

Generate the QR as BufferedImage (MatrixToImageWriter.toBufferedImage).
Load logo, scale to ~15–25% of QR size.
Draw logo centered using Graphics2D with anti-aliasing.
Ensure error correction level is at least Q or H so scanning still works.

Tips for production

Test with multiple scanner apps/devices.
For print use higher DPI and larger pixel size.
Avoid heavy foreground patterns that reduce contrast.
Use high error correction when embedding logos.
Cache generated images for repeated requests.

Troubleshooting

Blank or unreadable QR: increase size, margin, or error correction.
Non-ASCII text appears wrong: ensure UTF-8 encoding.
Too dense or scanner fails: reduce data (shorten URL) or increase module size.

Minimal web-service example (Spring Boot)

Expose an endpoint that returns image/png generated on-the-fly using the same ZXing code and writing to HttpServletResponse output stream.

Quick summary

Use ZXing with proper hints (UTF-8, error correction), choose an appropriate size and margin, and optionally customize colors or embed a logo. Test across devices and increase error correction for logos or damage tolerance.

Java QR Code Generator