java代码url生成二维码图片

可以使用第三方库Zxing来生成二维码图片，具体实现可以参考以下Java代码：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.imageio.ImageIO;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.WriterException;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class QrCodeGenerator {
    public static void main(String[] args) throws WriterException, IOException {
        String url = "https://www.example.com";
        int width = 300;
        int height = 300;
        String format = "png";
        File qrFile = new File("qrcode.png");
        Map<EncodeHintType, Object> hintMap = new HashMap<EncodeHintType, Object>();
        hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
        createQRCode(url, width, height, format, hintMap, qrFile);
    }

    private static void createQRCode(String url, int width, int height, String format, Map hintMap, File qrFile)
            throws WriterException, IOException {
        BitMatrix matrix = new MultiFormatWriter().encode(new String(url.getBytes("UTF-8"), "ISO-8859-1"),
                BarcodeFormat.QR_CODE, width, height, hintMap);
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        image.createGraphics();
        java.awt.Graphics2D graphics = (java.awt.Graphics2D) image.getGraphics();
        graphics.setColor(java.awt.Color.WHITE);
        graphics.fillRect(0, 0, width, height);
        graphics.setColor(java.awt.Color.BLACK);
        for (int i = 0; i < height; i++) {
            for (int j = 0; j < width; j++) {
                if (matrix.get(i, j)) {
                    graphics.fillRect(i, j, 1, 1);
                }
            }
        }
        ImageIO.write(image, format, qrFile);
    }
}

该代码可以生成一个指定URL的二维码图片，保存在本地文件qrcode.png中。