QRcode二维码生成，并跳转到指定的路径

具体实现步骤如下：
1.导入pom依赖：

    
        com.google.zxing
        core
        3.4.0
    
    
        com.google.zxing
        javase
        3.4.0
    

2.编写一个工具类
package com.example.util;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.HashMap;

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.client.j2se.MatrixToImageConfig;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.CharacterSetECI;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class ZxingUtils {

/**
 * // 二维码生成
 * @param contents 说明
 * @param width 宽
 * @param height 高
 * @param margin 边框
 * @return BufferedImage
 * @throws Exception
 */
public static BufferedImage createQRImage(String contents, int width, int height, int margin) throws Exception {
    BufferedImage qRImage = null;

    if (contents == null || "".equals(contents)) {
        throw new Exception("content说明不能为空");
    }

    // 二维码参数设置
    HashMap hints = new HashMap<>();
    hints.put(EncodeHintType.CHARACTER_SET, CharacterSetECI.UTF8); // 编码设置
    hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H); // 安全等级，最高h
    hints.put(EncodeHintType.MARGIN, margin); // 设置margin=0-10

    // 二维码图片的生成
    BarcodeFormat format = BarcodeFormat.QR_CODE;

    // 创建矩阵容器

    BitMatrix matrix = null;

    try {
        matrix = new MultiFormatWriter().encode(contents, format, width, height, hints);
    } catch (WriterException e) {
        e.printStackTrace();
    }

    // 设置矩阵转为图片的参数
    MatrixToImageConfig toImageConfig = new MatrixToImageConfig(Color.black.getRGB(), Color.white.getRGB());

    // 矩阵转换图像
    qRImage = MatrixToImageWriter.toBufferedImage(matrix, toImageConfig);

    return qRImage;
}

public static BufferedImage addQRImagelogo(BufferedImage qrImage, int width, int height, String logoPath, int logoSize) throws Exception {
// 二维码添加logo
    BufferedImage qRImageWithLogo = null;
    File logoFile = new File(logoPath);
    if (!logoFile.exists() || !logoFile.isFile()) {
        throw new Exception("指定的logo图片不存在");
    }

    // 处理logo
    BufferedImage image = ImageIO.read(logoFile);
    // 设置logo的高和宽
    int logoHeight = qrImage.getHeight()/logoSize;
    int logoWidth = qrImage.getWidth()/logoSize;
    // 设置放置位置
    int x = (qrImage.getHeight() - logoHeight) / 2;
    int y = (qrImage.getWidth() - logoWidth) / 2;

    // 新建画板
    qRImageWithLogo = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    // 新建画笔
    Graphics2D g = (Graphics2D) qRImageWithLogo.getGraphics();
    // 将二维码绘制到画板
    g.drawImage(qrImage, 0, 0, null);
    // 设置头透明度，可设置范围0.0f-1.0f
    g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1.0f));
    // 绘制logo
    g.drawImage(image, x, y, logoWidth, logoHeight, null);

    return qRImageWithLogo;
}}

3.编写service类
package com.example.service;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import com.sun.org.apache.xml.internal.security.utils.Base64;
import org.springframework.stereotype.Service;
import org.thymeleaf.util.StringUtils;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;

@Service
public class QRCodeService {
public String crateQRCode(String content,int width,int height) throws IOException{
String resultImage = “”;
if(!StringUtils.isEmpty(content)){
ServletOutputStream stream = null;
ByteArrayOutputStream os = new ByteArrayOutputStream();
@SuppressWarnings(“rawtypes”)
HashMap hints = new HashMap<>();
hints.put(EncodeHintType.CHARACTER_SET,“utf-8”);
hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);//指定二维码的纠错等级为中级
hints.put(EncodeHintType.MARGIN,2); //设置图片边距

       try {
           QRCodeWriter writer = new QRCodeWriter();
           BitMatrix bitMatrix = writer.encode(content, BarcodeFormat.QR_CODE, width, height, hints);

           BufferedImage bufferedImage = MatrixToImageWriter.toBufferedImage(bitMatrix);
           ImageIO.write(bufferedImage, "png", os);
           /**
            * 原生转码前面没有 data:image/png;base64 这些字段，返回给前端是无法被解析，可以让前端加，也可以在下面加上
            */
           resultImage = new String("data:image/png;base64," + Base64.encode(os.toByteArray()));

           return resultImage;
       } catch (Exception e) {
           e.printStackTrace();
       } finally {
           if (stream != null) {
               stream.flush();
               stream.close();
           }
       }

   }
    return null;
}

}
4.编写controller
package com.example.conroller;

import com.example.util.ZxingUtils;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

@Controller
public class DemoControler {

// 和验证码的实现原理是一样，是不过换了一种验证方式。
@RequestMapping("/createQRcode")
public void createQRcode(HttpServletResponse response)throws IOException {

    String contents = "https://www.baidu.com/";
    int width = 100;
    int height = 100;
    int margin = 2;


    try {
        BufferedImage QRcode = ZxingUtils.createQRImage(contents, width, height, margin);
        String logoPath = "C:\\Users\\Administrator\\Desktop\\spring boot资料\\aaa.png";
        int logoSize = 4;
        BufferedImage qRImageWithLogo = ZxingUtils.addQRImagelogo(QRcode, width, height, logoPath, logoSize);

        // 写入返回
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ImageIO.write(qRImageWithLogo, "jpg", baos);

        byte[] QRJPG = baos.toByteArray();
        response.setHeader("Cache-Control", "no-store");
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");


        //写入本地磁盘
        OutputStream os2 = new FileOutputStream("C:\\Users\\Administrator\\Desktop\\newbee-mall\\text.png");
        os2.write(QRJPG, 0, QRJPG.length);
        os2.flush();
        os2.close();

        ServletOutputStream os = response.getOutputStream();
        os.write(QRJPG); // 自此完成一套，图片读入，写入流，转为字节数组，写入输出流
        os.flush();
        os.close();
        baos.close();

    } catch (Exception e) {
        e.printStackTrace();
    }
    response.sendRedirect(contents);  //扫码后跳转百度
}

}