如何在 Vaadin 中将字符串转换为二维码图像？

Question

我有一个类似的字符串

String s = "123456789";

我想要一个带有从字符串生成的 QrCode 的 Vaadin 图像，以将其显示在窗口中。所以我想要这样的东西：

public Image toQr(String s) {
    <...>
    return imageOfQr;
}
add(toQr("Hello World"));

我该怎么做？ 您能帮我提供具有相同输入和输出的完整方法吗？我对任何其他输出不感兴趣。

Answer 1

这是一个示例类，说明如何以两种不同的方式执行此操作。我还会检查 ZXingVaadin 插件，它可能会做类似的事情（我从未尝试过）。

package org.example.views;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.oned.EAN13Writer;
import com.vaadin.flow.component.html.Image;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.router.Route;
import com.vaadin.flow.server.AbstractStreamResource;
import com.vaadin.flow.server.StreamResource;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

@Route
public class BarcodeView extends VerticalLayout {

    public BarcodeView() {
        String barcodeText = "123456789012";

        Image barcode = new Image();
        barcode.setSrc(asStreamResource(generateEAN13BarcodeImage(barcodeText)));
        add(barcode);

        // Barcode images are typically small
        // & no need for caching, using as data URL is fine as well
        Image asDataUrl = new Image();
        asDataUrl.setSrc(toDataUrl(generateEAN13BarcodeImage(barcodeText)));
        add(asDataUrl);


    }

    private AbstractStreamResource asStreamResource(BufferedImage bufferedImage) {
        return new StreamResource("barcode.png", (output, session) -> {
            try {
                ImageIO.write(bufferedImage, "png", output);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        });
    }

    public static final int BARCODE_W = 300;
    public static final int BARCODE_H = 50;

    public static BufferedImage generateEAN13BarcodeImage(String barcodeText) {
        EAN13Writer barcodeWriter = new EAN13Writer();
        BitMatrix bitMatrix = barcodeWriter.encode(barcodeText, BarcodeFormat.EAN_13, BARCODE_W, BARCODE_H);
        return MatrixToImageWriter.toBufferedImage(bitMatrix);
    }

    public String toDataUrl(BufferedImage image) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            ImageIO.write(image, "png", baos);
            return "data:image/png;base64," + jakarta.xml.bind.DatatypeConverter.printBase64Binary(baos.toByteArray());
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

}