1. 二维码基础

1.1概念

二维码：某种特定几何图形按一定规律在平面上分布的条，空相间的图形来记录数据符号的信息。

1.2分类

线性堆叠式二维码；

矩阵式二维码；

邮政码。

2.国家标准GB

3.QR Code类二维码

3.1ZXing工具生成/解析

ZXing: https://github.com/zxing

需要引入zxing-3.2.1.jar

package com.wdy.utils;

import com.google.common.collect.Maps;
import com.google.zxing.*;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.HybridBinarizer;
import com.google.zxing.datamatrix.encoder.ErrorCorrection;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import org.apache.http.HttpResponse;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.*;
import java.io.Writer;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;

/**
* Created by wangdy on 2017/7/20.
*/
public class ZXingUtil {

    public static void main(String[] args) {
//        createZXingQRCodeToFile(300, 300, "png", "I am wangdy，哈哈", "qrcode.png");
        Map<String, Object> stringObjectMap = readZXingQRCodeToFile("qrcode.png");
        System.out.println("" + stringObjectMap.get("result"));

    }

    /**
     * 使用ZXing工具生成qrcode二维码---到文件
     *
     * @param width    宽度
     * @param height   高度
     * @param format   扩展名 eg png
     * @param content  文字内容
     * @param filePath 输出文件路径
     * @date:2017/7/20 23:29
     */
    public static void createZXingQRCodeToFile(int width, int height, String format, String content, String filePath) {
        HashMap hints = new HashMap();
        //设置文字编码
        hints.put(EncodeHintType.CHARACTER_SET, "utf-8");
        //设置容错等级，常用M
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);
        //设置二维码四周空白，默认5
        hints.put(EncodeHintType.MARGIN, 2);
        try {
            BitMatrix bitMatrix = new MultiFormatWriter().encode(content, BarcodeFormat.QR_CODE, width, height, hints);
            Path path = new File(filePath).toPath();
            MatrixToImageWriter.writeToPath(bitMatrix, format, path);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 使用ZXing工具解析二维码
     *
     * @param filePath 文件路径
     * @date:2017/7/20 23:29
     * @return Map:<"result",value>,<"textResult",value>,<"barcodeFormat",value>
     */
    public static Map<String, Object> readZXingQRCodeToFile(String filePath) {
        Map<String, Object> resultMap = Maps.newHashMap();
        MultiFormatReader multiFormatReader = new MultiFormatReader();
        File file = new File(filePath);
        try {
            BufferedImage bufferedImage = ImageIO.read(file);
            BinaryBitmap binaryBitmap = new BinaryBitmap(new HybridBinarizer(new BufferedImageLuminanceSource(bufferedImage)));
            HashMap hints = new HashMap();
            //设置文字编码
            hints.put(EncodeHintType.CHARACTER_SET, "utf-8");
            Result result = multiFormatReader.decode(binaryBitmap, hints);

            System.out.println("解析结果： " + result.toString());
            System.out.println("解析文本内容：" + result.getText());
            System.out.println("二维码类型：" + result.getBarcodeFormat());
            /*解析结果： I am wangdy，哈哈
            解析文本内容：I am wangdy，哈哈
            二维码类型：QR_CODE*/

            resultMap.put("result", result.toString());
            resultMap.put("textResult", result.getText());
            resultMap.put("barcodeFormat", result.getBarcodeFormat());
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resultMap;
    }

3.2QECode工具生成/解析

生成二维码jar：http://www.swetake.com/qrcode/

解析二维码jar：https://zh.osdn.net/projects/qrcode/

1)将下载下来的jar重命名后，安装到本地maven仓库中：

2）引入到工程

3）代码：

package com.wdy.utils;
  
  import com.swetake.util.Qrcode;
  import jp.sourceforge.qrcode.QRCodeDecoder;
  
  import javax.imageio.ImageIO;
  import java.awt.*;
  import java.awt.image.BufferedImage;
  import java.io.File;
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  
  /**
 * 使用QRCode工具生成解析二维码
 * Created by wangdy on 2017/7/21.
 */
  public class QRCodeUtil {
    /**
     * 使用QRCode工具生成 二维码
     *
     * @param qrcodeVersion 版本号 一般用7
     * @param content       填充文字
     * @param format        扩展名 如png
     * @param filePath      生成的文件路径
     * @return
     * @date:2017/7/21 10:10
     */
    public static void createQRCByQRCode(int qrcodeVersion, String content, String format, String filePath) {
        Qrcode qrcode = new Qrcode();
        qrcode.setQrcodeErrorCorrect('M');
        //N代表数字，A代表字母，B代表其他字符，通常B
        qrcode.setQrcodeEncodeMode('B');
        qrcode.setQrcodeVersion(qrcodeVersion);//版本号
        int width = 67 + 12 * (qrcodeVersion - 1);//固定公式
        int height = 67 + 12 * (qrcodeVersion - 1);
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
  
        Graphics2D graphics2D = bufferedImage.createGraphics();
        graphics2D.setBackground(Color.WHITE);
        graphics2D.setColor(Color.BLACK);
        graphics2D.clearRect(0, 0, width, height);
  
        int pixoff = 2;//偏移量,绘图使用
  
        byte[] bytes = new byte[0];
        try {
            bytes = content.getBytes("utf-8");//中文支持
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        if (bytes.length > 0 && bytes.length < 120) {
            boolean[][] s = qrcode.calQrcode(bytes);
            for (int i = 0; i < s.length; i++) {
                for (int j = 0; j < s.length; j++) {
                    if (s[j][i]) {
                        graphics2D.fillRect(j * 3 + pixoff, i * 3 + pixoff, 3, 3);
                    }
                }
            }
            graphics2D.dispose();
            bufferedImage.flush();
            try {
                File file = new File(filePath);
                boolean write = ImageIO.write(bufferedImage, format, file);
                if (write) {
                    System.out.println("生成二维码成功：位置" + file.getAbsolutePath());
                    //生成二维码成功：位置E:\mycode\jdbcTempDemo\qrcodecreate.png
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
  
  
    /**
     * 使用QRCode工具生成 二维码
     *
     * @param filePath 生成的文件路径
     * @return
     * @date:2017/7/21 10:10
     */
    public static String readQRCByQRCode(String filePath) {
        File file = new File(filePath);
        String result = "";
        try {
            BufferedImage bufferedImage = ImageIO.read(file);
            QRCodeDecoder qrCodeDecoder = new QRCodeDecoder();
  //            byte[] decode = qrCodeDecoder.decode(new MyQRCodeImage(bufferedImage));
            result = new String(qrCodeDecoder.decode(new MyQRCodeImage(bufferedImage)), "utf-8");
            System.out.println("解析结果为：" + result);
  
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
  
    public static void main(String[] args) {
  //        createQRCByQRCode(7, "I am your father,哦也！", "png", "qrcodecreate.png");
        String result = readQRCByQRCode("123.png");
        System.out.println("" + result);
    }
}

3.3jquery-qrcode生成二维码

https://github.com/jeromeetienne/jquery-qrcode

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
  <html>
<head>
    <title>Title</title>
    <%--注意顺序--%>
    <script type="text/javascript" src="<%=request.getContextPath() %>/js/jquery.min.js"></script>
    <script type="text/javascript" src="<%=request.getContextPath() %>/js/jquery.qrcode.min.js"></script>
</head>
<body>
  生成的二维码如下：

<%--注意顺序--%>

<div id="qrcode"></div><script type="text/javascript"> jQuery('#qrcode').qrcode({width: 120, height: 120, text: utf16to8("this is content中12文")});

//支持中文方法
    function utf16to8(str) {
        var out, i, len, c;
        out = "";
        len = str.length;
        for (i = 0; i < len; i++) {
            c = str.charCodeAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)) {
                out += str.charAt(i);
            } else if (c > 0x07FF) {
                out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
                out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            } else {
                out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            }
        }
        return out;
    }
</script>
</body>
</html>

特别注意问题：jquery-qrcode生成的二维码用微信/支付宝可以正常扫描，用ZxingUtil工具也可以解析，但用QRCode.jar无法正常解析，错误如下/还有一种可能是解析出的是乱码。

jp.sourceforge.qrcode.exception.DecodingFailedException: Give up decoding

        at jp.sourceforge.qrcode.QRCodeDecoder.decode(QRCodeDecoder.java:88)

        at com.wdy.utils.QRCodeUtil.readQRCByQRCode(QRCodeUtil.java:90)

        at com.wdy.utils.QRCodeUtil.main(QRCodeUtil.java:101)

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

        at java.lang.reflect.Method.invoke(Method.java:483)

        at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

工具（十）：Java二维码操作工具类