QRCode.java

import com.google.zxing.BinaryBitmap;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.Result;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.common.HybridBinarizer;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

import javax.imageio.ImageIO;
import java.io.ByteArrayInputStream;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

/**
 * QrCode decoder class
 */
public class QrCodeDecoder
{

    /**
     * Decodes QrCodeDecoder from image content encoded with Base64
     *
     * @param qrcodeBase64
     * @return String
     */
    public static String decode(String qrcodeBase64)
    {
        String decodedString;
        try {
            // decodes base64 string
            byte[] qrCodeBytes = Base64.getDecoder().decode(qrcodeBase64.getBytes(StandardCharsets.UTF_8));

            Map hintMap = new HashMap();
            hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);

            // decodes QrCodeDecoder
            BinaryBitmap binaryBitmap = new BinaryBitmap(
                new HybridBinarizer(
                    new BufferedImageLuminanceSource(
                        ImageIO.read(
                            new ByteArrayInputStream(qrCodeBytes)
                        )
                    )
                )
            );
            Result qrCodeResult = new MultiFormatReader().decode(binaryBitmap, hintMap);
            decodedString = qrCodeResult.getText();
        } catch (Exception e) {
            decodedString = "";
        }

        return decodedString;
    }
}