后端生成二维码，以流的形式返回到前端

先引入QRCode的依赖

<!-- https://mvnrepository.com/artifact/QRCode/QRCode_swetake -->
        <dependency>
            <groupId>QRCode</groupId>
            <artifactId>QRCode_swetake</artifactId>
            <version>3.0.0</version>
        </dependency>

QRCode工具类

package com.hrt.zxxc.fxspg.qrcode;


import com.swetake.util.Qrcode;


import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;


/**
* @ProjectName: fxspg
* @Package: com.hrt.zxxc.fxspg.qrcode
* @ClassName: CodeUtils
* @Author: wls
* @Description: ${description}
* @Version: 1.0
*/
public class CodeUtils {
    public void encoderQRCoder(String content, HttpServletResponse response) {
        try {
            Qrcode handler = new Qrcode();
            handler.setQrcodeErrorCorrect('M');
            handler.setQrcodeEncodeMode('B');
            handler.setQrcodeVersion(7);
            byte[] contentBytes = content.getBytes("UTF-8");
            BufferedImage bufImg = new BufferedImage(140, 140, BufferedImage.TYPE_INT_RGB);
            Graphics2D gs = bufImg.createGraphics();
            gs.setBackground(Color.WHITE);
            gs.clearRect(0, 0, 140, 140);
            //设定图像颜色：BLACK
            gs.setColor(Color.BLACK);
            //设置偏移量  不设置肯能导致解析出错
            int pixoff = 2;
            //输出内容：二维码
            if(contentBytes.length > 0 && contentBytes.length < 124) {
                boolean[][] codeOut = handler.calQrcode(contentBytes);
                for(int i = 0; i < codeOut.length; i++) {
                    for(int j = 0; j < codeOut.length; j++) {
                        if(codeOut[j][i]) {
                            gs.fillRect(j * 3 + pixoff, i * 3 + pixoff,3, 3);
                        }
                    }
                }
            } else {
                System.err.println("QRCode content bytes length = " + contentBytes.length + " not in [ 0,120 ]. ");
            }
            gs.dispose();
            bufImg.flush();
            //生成二维码QRCode图片
            ImageIO.write(bufImg, "jpg", response.getOutputStream());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

@GetMapping("qrCode")
public void qrCode(HttpServletRequest requset, HttpServletResponse response) throws ServletException, IOException {    
	ptfQuotationFormService.qrCode(requset,response);
}

public void qrCode(HttpServletRequest requset, HttpServletResponse response)throws ServletException, IOException {
    String content = "http://120.79.174.47";
    CodeUtils encoder = new CodeUtils();
    encoder.encoderQRCoder(content, response);
}