1，先引入谷歌的插件zxing的maven坐标

 <!-- 二维码 -->
        <dependency>
            <groupId>com.google.zxing</groupId>
            <artifactId>core</artifactId>
            <version>3.4.1</version>
        </dependency>
        <dependency>
            <groupId>com.google.zxing</groupId>
            <artifactId>javase</artifactId>
            <version>3.4.1</version>
        </dependency>

2，然后复制下面的工具类，使用即可

package com.sport.sportactivityserver.common.utils;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import org.apache.commons.codec.binary.Base64;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class QRCodeGenerator {
    // 生成二维码高度
    public static final int width = 350;
    
    // 生成二维码宽度
    public static final int height = 350;

    /**
     * 生成二维码
     * @param text  二维码内容
     * @return 返回二维码的base64编码
     */
    public static String generateQRCodeImage(String text) {
        try {
            return generateQRCodeImage(text, width, height);
        } catch (WriterException | IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 生成二维码
     * @param text  二维码内容
     * @param width  二维码高度
     * @param height 二维码宽度
     * @return 返回二维码的base64编码
     * @throws WriterException
     * @throws IOException
     */
    private static String generateQRCodeImage(String text, int width, int height) throws WriterException, IOException {
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        BitMatrix bitMatrix = qrCodeWriter.encode(text, BarcodeFormat.QR_CODE, width, height);
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        MatrixToImageWriter.writeToStream(bitMatrix, "PNG", outputStream);
        byte[] imgByte = Base64.encodeBase64(outputStream.toByteArray());
        return "data:image/png;base64," + new String(imgByte);
    }
    
    
    public static void main(String[] args) {
        try {
            String s = generateQRCodeImage("This is my first QR Code", 350, 350);
            System.out.println(s);
        } catch (WriterException e) {
            System.out.println("Could not generate QR Code, WriterException :: " + e.getMessage());
        } catch (IOException e) {
            System.out.println("Could not generate QR Code, IOException :: " + e.getMessage());
        }
    }
}

3，结果