java支付寶生成二維碼

在對接支付寶面對面支付的開發中，商戶系統會向支付寶發起預下單請求，預下單請求成功后支付寶會返回給商戶系統一個支付二維碼的鏈接地址，因此需要用戶把該二維碼生成一個二維碼圖片到前端展示給用戶掃碼支付使用。

調用支付寶預下單接口alipay.trade.precreate請求生成二維碼鏈接

搭建步驟

1.導入依賴

<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>core</artifactId>
    <version>3.4.1</version>
</dependency>

2.創建工具類QRCodeUtil

package com.sean.alipayf2f.utils;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Map;

/**
 * @author : sean
 * @version V1.0
 * @Project: alipayf2f
 * @Package com.sean.alipayf2f.utils
 * @date Date : 2021年07月22日 14:54
 */

public class QrCodeUtil {
    private static Log log = LogFactory.getLog(QrCodeUtil.class);

    private static final int BLACK = 0xFF000000;
    private static final int WHITE = 0xFFFFFFFF;

    private static BufferedImage toBufferedImage(BitMatrix matrix) {
        int width = matrix.getWidth();
        int height = matrix.getHeight();
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        for (int x = 0; x < width; x++) {
            for (int y = 0; y < height; y++) {
                image.setRGB(x, y, matrix.get(x, y) ? BLACK : WHITE);
            }
        }
        return image;
    }

    private static void writeToFile(BitMatrix matrix, String format, File file) throws IOException {
        BufferedImage image = toBufferedImage(matrix);
        if (!ImageIO.write(image, format, file)) {
            throw new IOException("Could not write an image of format " + format + " to " + file);
        }
    }

    /** 將內容contents生成長寬均為width的圖片，圖片路徑由imgPath指定
     */
    public static File getQRCodeImge(String contents, int width, String imgPath) {
        return getQRCodeImge(contents, width, width, imgPath);
    }

    /** 將內容contents生成長為width，寬為width的圖片，圖片路徑由imgPath指定
     */
    public static File getQRCodeImge(String contents, int width, int height, String imgPath) {
        try {
            Map<EncodeHintType, Object> hints = new Hashtable<EncodeHintType, Object>();
            hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);
            hints.put(EncodeHintType.CHARACTER_SET, "UTF8");

            BitMatrix bitMatrix = new MultiFormatWriter().encode(contents, BarcodeFormat.QR_CODE, width, height, hints);

            File imageFile = new File(imgPath);
            writeToFile(bitMatrix, "png", imageFile);

            return imageFile;

        } catch (Exception e) {
            log.error("create QR code error!", e);
            return null;
        }
    }
}

3.測試

 @Test
    void qrcodeTest()
    {
        // 需要修改為運行機器上的路徑
        String path = "C:\\Users\\sean\\Desktop\\F2FPay_Demo_Java";

        String qrPath = String.format(path + "\\qr-%s.png", "111111111111111");
        String qrFileName = String.format("qr-%s.png", "111111111111111");
        QrCodeUtil.getQRCodeImge("https:\\/\\/qr.alipay.com\\/bax014525dld1hiylvni0051", 256, qrPath);

        File targetFile = new File(path, qrFileName);
        
    }

以上方法是將生成的二維碼保存到本地，如果需要將二維碼圖片返回到前端展示，可以用如下方法

//向支付寶發送預下單請求
AlipayTradePrecreateResponse payResponse =alipayClient.execute(payRequest);
//二維碼鏈接生成二維碼圖片
String qrPath = String.format("\\qr-%s.png", payResponse.getOutTradeNo());
String qrFileName = String.format("qr-%s.png", payResponse.getOutTradeNo());
QrCodeUtil.getQRCodeImge(payResponse.getQrCode(), 256, qrPath);
File targetFile = new File(path, qrFileName);
//通過流的方式將二維碼圖片返回
ServletOutputStream  out = response.getOutputStream();
ImageIO.write(ImageIO.read(targetFile),"jpg",out);		
out.flush();

java response 圖片流:
https://blog.csdn.net/weixin_34169503/article/details/114110548