生成二维码，扫码跳转连接

首先前台使用的是vue，用到的生成二维码工具类ZxingUtil

 <a v-bind:href="'${ctx}/admin/activity/activityDetailQRCode.do?recno='+item.recno"
                                               class="btn btn-danger btn-xs" v-bind:download="item.name+'.jpg'"
                                               style="padding:1px 5px;font-size: 14px;margin-top: 5px">下载活动报名二维码</a>

后台

 //生成活动报名二维码
    @RequestMapping("activityDetailQRCode")
    @ResponseBody
    public void activityDetailQRCode(HttpServletRequest request,HttpServletResponse response,Integer recno){
        String realPath = request.getServletContext().getRealPath("/");
        File dir = new File(realPath+File.separator+"activityDetailQRCode");
        if(!dir.exists()){
            dir.mkdir();
        }

        String activityQrcodeLink = dir.getAbsolutePath() + File.separator  + recno + ".jpg";
        File file = new File(activityQrcodeLink);
        if (!file.exists()) {
            try {
                file.createNewFile();
                //获取网络协议
                String networkProtocol = request.getScheme();
                //网络IP
                String ip = request.getServerName();
                //端口号
                int port = request.getServerPort();
                //项目发布路径
                String webApp = request.getContextPath();
                //url:${ctx}/mobile/activity/activityDetail.do?activityRecno=" + recno
                String activityDetailQrcodeLink = networkProtocol+"://"+ip+":"+port+webApp+"/mobile/activity/activityDetail.do?activityRecno="+recno;
                ZxingUtil.encode2DCode(file, activityDetailQrcodeLink);
            } catch (WriterException | IOException e) {
                e.printStackTrace();
            }
        }
        response.setContentType("image/jpg");
        BufferedInputStream inputStream =null;
        BufferedOutputStream outputStream = null;
        try {
            inputStream = new BufferedInputStream(new FileInputStream(file));
            outputStream = new BufferedOutputStream(response.getOutputStream());
            flushStream(inputStream, outputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(inputStream!=null){
                    inputStream.close();
                }
                if(outputStream!=null){
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }


    }

然后调用一个方法，刷新缓冲流

private void flushStream(InputStream fis, OutputStream os) throws IOException {//刷新字节流
    int count = 0;
    byte[] buffer = new byte[1024 * 8];
    while ((count = fis.read(buffer)) != -1) {
        os.write(buffer, 0, count);
        os.flush();
    }
}

　　----补充 之前一直有人找我要工具类 我现在贴下面

　　　然后的话需要两个依赖

　　    这里把maven依赖贴上

        <dependency>
            <groupId>com.google.zxing</groupId>
            <artifactId>core</artifactId>
            <version>3.3.0</version>
        </dependency>

　　

package com.common.utils;

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 javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;

public class ZxingUtil {
	private static final int BLACK = 0xFF000000;
	private static final int WHITE = 0xFFFFFFFF;

	private static final int DEFAULT_HEIGHT = 300;// 二维码图片宽度
	private static final int DEFAULT_WIDTH = 300;// 二维码图片高度
	private static final String DEFAULT_FORMAT = "gif";// 二维码的图片格式

	private static final int BARCODE_HEIGHT = 30;
	private static final int BARCODE_WIDTH = 150;
	private static final String BARCODE_FORMAT = "png";

	/**
	 * 生成二维码 到指定 路径 、
	 *
	 * @param outputStream
	 *            到指定 路径 、FILE
	 * @param text
	 *            可以是网址 和 其他，网址就是跳转
	 * @throws WriterException
	 * @throws IOException
	 */
	public static void encode2DCode(OutputStream outputStream, String text)
			throws WriterException, IOException {
		Map<EncodeHintType, Object> hints = new HashMap<EncodeHintType, Object>();
		hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); // 内容所使用字符集编码
		hints.put(EncodeHintType.MARGIN, 1);
		BitMatrix bitMatrix = new MultiFormatWriter().encode(text,
				BarcodeFormat.QR_CODE, DEFAULT_WIDTH, DEFAULT_HEIGHT, hints);

        BufferedImage image = toBufferedImage(bitMatrix);
        /*
         * Graphics2D gs = image.createGraphics(); //载入logo Image img =
         * ImageIO.read(new File(srcImagePath)); gs.drawImage(img, 125, 125,
         * null); gs.dispose(); img.flush();
         */
        if (!ImageIO.write(image, DEFAULT_FORMAT, outputStream)) {
            throw new IOException("Could not write an image of format "
                    + DEFAULT_FORMAT + " to stream");
        }
	}

	/**
	 * 返回BitMatrix二维码内容
	 * @param text
	 * @return
	 * @throws WriterException
	 */
	public static BitMatrix encode2DCode(String text) throws WriterException {
		Map<EncodeHintType, Object> hints = new HashMap<EncodeHintType, Object>();
		hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); // 内容所使用字符集编码
		hints.put(EncodeHintType.MARGIN, 1);
		BitMatrix bitMatrix = new MultiFormatWriter().encode(text,
				BarcodeFormat.QR_CODE, DEFAULT_WIDTH, DEFAULT_HEIGHT, hints);
		return bitMatrix;
	}

	/**
	 *
	 * @param outputFile
	 *            到指定路径
	 * @param text
	 *            可以是网址 和 其他内容，网址就是跳转
	 * @param width
	 *            二维码 宽度
	 * @param height
	 *            二维码高度
	 * @param format
	 *            生成二维码的图片格式
	 * @throws WriterException
	 * @throws IOException
	 */
	public static void encode2DCode(File outputFile, String text, int width,
			int height, String format) throws WriterException, IOException {
		// 读取源图像
		Map<EncodeHintType, String> hints = new HashMap<EncodeHintType, String>();
		hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); // 内容所使用字符集编码
		BitMatrix bitMatrix = new MultiFormatWriter().encode(text,
				BarcodeFormat.QR_CODE, width, height, hints);
		writeToFile(bitMatrix, format, outputFile);
	}

	/**
	 * 生成条码号
	 *
	 * <p>2017年1月17日 下午1:56:33
	 * <p>create by hjc
	 * @throws WriterException
	 * @throws IOException
	 */
	public static void encodeBarcode(File outputFile, String text) throws WriterException, IOException{
		Map<EncodeHintType, Object> hints = new HashMap<EncodeHintType, Object>();
//		hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); // 内容所使用字符集编码
//		hints.put(EncodeHintType.MARGIN, 1);
		BitMatrix bitMatrix = new MultiFormatWriter().encode(text,
				BarcodeFormat.CODE_128, BARCODE_WIDTH, BARCODE_HEIGHT, hints);
		writeToFile(bitMatrix, BARCODE_FORMAT, outputFile);
	}


	public static BufferedImage toBufferedImage(BitMatrix matrix)
			throws IOException {
		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;
	}

	public static void writeToFile(BitMatrix matrix, String format, File file,String srcImagePath)
			throws IOException {
		BufferedImage image = toBufferedImage(matrix);
		  Graphics2D gs = image.createGraphics(); //载入logo
		  Image img = ImageIO.read(new File(srcImagePath));
		  gs.drawImage(img, 125, 125, null);
		  gs.dispose();
		  img.flush();
		if (!ImageIO.write(image, format, file)) {
			throw new IOException("Could not write an image of format "
					+ format + " to " + file);
		}
	}

	public static void writeToFile(BitMatrix matrix, String format, File file)
			throws IOException {
		BufferedImage image = toBufferedImage(matrix);
		/*
		 * Graphics2D gs = image.createGraphics(); //载入logo Image img =
		 * ImageIO.read(new File(srcImagePath)); gs.drawImage(img, 125, 125,
		 * null); gs.dispose(); img.flush();
		 */
		if (!ImageIO.write(image, format, file)) {
			throw new IOException("Could not write an image of format "
					+ format + " to " + file);
		}
	}

	public static void writeToStream(BitMatrix matrix, String format,
			OutputStream stream) throws IOException {
		BufferedImage image = toBufferedImage(matrix);
		if (!ImageIO.write(image, format, stream)) {
			throw new IOException("Could not write an image of format "
					+ format);
		}
	}

	/**
	 * 把传入的原始图像按高度和宽度进行缩放，生成符合要求的图标
	 *
	 * @param srcImageFile
	 *            源文件地址
	 * @param height
	 *            目标高度
	 * @param width
	 *            目标宽度
	 * @param hasFiller
	 *            比例不对时是否需要补白：true为补白; false为不补白;
	 * @throws IOException
	 */
	@SuppressWarnings("unused")
	private static BufferedImage scale(String srcImageFile, int height,
			int width, boolean hasFiller) throws IOException {
		double ratio = 0.0; // 缩放比例
		File file = new File(srcImageFile);
		BufferedImage srcImage = ImageIO.read(file);
		Image destImage = srcImage.getScaledInstance(width, height,
				BufferedImage.SCALE_SMOOTH);
		// 计算比例
		if ((srcImage.getHeight() > height) || (srcImage.getWidth() > width)) {
			if (srcImage.getHeight() > srcImage.getWidth()) {
				ratio = (new Integer(height)).doubleValue()
						/ srcImage.getHeight();
			} else {
				ratio = (new Integer(width)).doubleValue()
						/ srcImage.getWidth();
			}

			AffineTransformOp op = new AffineTransformOp(
					AffineTransform.getScaleInstance(ratio, ratio), null);
			destImage = op.filter(srcImage, null);
		}
		if (hasFiller) {// 补白
			BufferedImage image = new BufferedImage(width, height,
					BufferedImage.TYPE_INT_RGB);
			Graphics2D graphic = image.createGraphics();
			graphic.setColor(Color.white);
			graphic.fillRect(0, 0, width, height);
			if (width == destImage.getWidth(null))
				graphic.drawImage(destImage, 0,
						(height - destImage.getHeight(null)) / 2,
						destImage.getWidth(null), destImage.getHeight(null),
						Color.white, null);
			else
				graphic.drawImage(destImage,
						(width - destImage.getWidth(null)) / 2, 0,
						destImage.getWidth(null), destImage.getHeight(null),
						Color.white, null);
			graphic.dispose();
			destImage = image;
		}
		return (BufferedImage) destImage;
	}

	public static void scale(String srcImageFile, String result, int scale,
			boolean flag) {
		try {
			BufferedImage src = ImageIO.read(new File(srcImageFile)); // 读入文件
			int width = src.getWidth(); // 得到源图宽
			int height = src.getHeight(); // 得到源图长
			if (flag) {
				// 放大
				width = width * scale;
				height = height * scale;
			} else {
				// 缩小
				width = width / scale;
				height = height / scale;
			}
			Image image = src.getScaledInstance(width, height,
					Image.SCALE_SMOOTH);
			BufferedImage tag = new BufferedImage(width, height,
					BufferedImage.TYPE_INT_RGB);
			Graphics g = tag.getGraphics();
			g.drawImage(image, 0, 0, null); // 绘制缩小后的图
			g.dispose();
			ImageIO.write(tag, "JPEG", new File(result));// 输出到文件流
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}