如何使用 Java 生成二维码？

mvn install:install-file
-DgroupId=包名
-DartifactId=项目名
-Dversion=版本号
-Dpackaging=jar-Dfile=jar文件所在路径

1，本地D盘中有个jar，例如：D:\work\Repository\QRCode.jar

2，cmd 中执行mvn install

命令格式为：mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> -DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>

例如：install-file -Dfile=D:\work\Repository\QRCode.jar -DgroupId=QRCode -DartifactId=QRCode -Dversion=3.0 -Dpackaging=jar  -DgeneratePom=true -DcreateChecksum=true

(注意空格)

3，在pom.xml中增加如下语句

<dependency>
   <groupId>QRCode</groupId>
   <artifactId>QRCode</artifactId>
   <version>3.0</version>
</dependency>

C:\Users\zhm>mvn install:install-file -Dfile=D:\work\Repository\QRCode.jar -DgroupId=QRCode -DartifactId=QRCode -Dversion=3.0 -Dpackaging=jar  -DgeneratePom=true -DcreateChecksum=true
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-install-plugin:2.4:install-file (default-cli) @ standalone-pom ---
[INFO] Installing D:\work\Repository\QRCode.jar to D:\work\Repository\QRCode\QRCode\3.0\QRCode-3.0.jar
[INFO] Installing C:\Users\zhm\AppData\Local\Temp\mvninstall6966241826790879082.pom to D:\work\Repository\QRCode\QRCode\3.0\QRCode-3.0.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.604 s
[INFO] Finished at: 2018-09-30T15:16:23+08:00
[INFO] Final Memory: 7M/123M
[INFO] ------------------------------------------------------------------------
    或者不做以上操作引入jar包，pom文件直接指向QRCode.jar在本地路径

<dependency>
    <groupId>QRCode</groupId>
    <artifactId>QRCode</artifactId>
    <version>3.0</version>
    <scope>system</scope>
    <systemPath>D:/work/Repository/QRCode.jar</systemPath>
</dependency>

package com.st.project.common;

import com.swetake.util.Qrcode;
import jp.sourceforge.qrcode.QRCodeDecoder;
import jp.sourceforge.qrcode.data.QRCodeImage;
import jp.sourceforge.qrcode.exception.DecodingFailedException;

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

/**
 * 二维码工具类
 */
public class CreateQRCode {

    /**
     * 创建二维码
     * @param qrData 生成二维码中要存储的信息
     * @param path   二维码图片存储路径 eg："D:/qrcode.png"
     * @throws Exception
     */
    public static boolean creatQrcode(String qrData, String path) {
        try {
            Qrcode qrcode = new Qrcode();
            qrcode.setQrcodeErrorCorrect('M');//纠错等级（分为L、M、H三个等级）
            qrcode.setQrcodeEncodeMode('B');//N代表数字，A代表a-Z，B代表其它字符
            qrcode.setQrcodeVersion(7);//版本

            //设置一下二维码的像素
            int width = 67 + 12 * (7 - 1);
            int height = 67 + 12 * (7 - 1);
            BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            //绘图
            Graphics2D gs = bufferedImage.createGraphics();
            gs.setBackground(Color.WHITE);
            gs.setColor(Color.BLACK);
            gs.clearRect(0, 0, width, height);//清除下画板内容

            //设置下偏移量,如果不加偏移量，有时会导致出错。
            int pixoff = 2;

            byte[] d = qrData.getBytes("utf-8");
            if (d.length > 0 && d.length < 120) {
                boolean[][] s = qrcode.calQrcode(d);
                for (int i = 0; i < s.length; i++) {
                    for (int j = 0; j < s.length; j++) {
                        if (s[j][i]) {
                            gs.fillRect(j * 3 + pixoff, i * 3 + pixoff, 3, 3);
                        }
                    }
                }
            }
            gs.dispose();
            bufferedImage.flush();
            ImageIO.write(bufferedImage, "png", new File(path));
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    /**
     * 解析二维码（QRCode）
     *
     * @param imgPath 图片路径
     * @return
     */
    public static String decoderQRCode(String imgPath) {
        //QRCode 二维码图片的文件
        File imageFile = new File(imgPath);
        BufferedImage bufImg = null;
        String content = null;
        try {
            bufImg = ImageIO.read(imageFile);
            QRCodeDecoder decoder = new QRCodeDecoder();
            content = new String(decoder.decode(new TwoDimensionCodeImage(bufImg)), "utf-8");
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
            e.printStackTrace();
        } catch (DecodingFailedException dfe) {
            System.out.println("Error: " + dfe.getMessage());
            dfe.printStackTrace();
        }
        return content;
    }

}

/**
 * 二维码基础类
 */
class TwoDimensionCodeImage implements QRCodeImage {
    //BufferedImage作用将一幅图片加载到内存中
    BufferedImage bufImg;
    public TwoDimensionCodeImage(BufferedImage bufImg) {
        this.bufImg = bufImg;
    }

    @Override
    public int getWidth() {
        return bufImg.getWidth();//返回像素宽度
    }

    @Override
    public int getHeight() {
        return bufImg.getHeight();//返回像素高度
    }

    @Override
    public int getPixel(int i, int i1) {
        return bufImg.getRGB(i, i1);//得到长宽值，即像素值，i,i1代表像素值
    }
}

package com.st.project.controller;

import com.st.project.common.AjaxResult;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;

import static com.st.project.common.CreateQRCode.creatQrcode;
import static com.st.project.common.CreateQRCode.decoderQRCode;

/**
 * 创建二维码
 */
@Controller
@RequestMapping("/qrcode")
public class QrcodeController {
    @Value("${portals.upload.image.path}")
    private String qrcodePath; //二维码存储路径

    /**
     * 创建二维码
     * @return
     */
    @ResponseBody
    @PostMapping("/add.dd")
    public AjaxResult addQrcode(HttpServletRequest request){
        AjaxResult ajaxResult = new AjaxResult();
        ajaxResult.setState(false);
        String qrData=request.getParameter("qrData");
        String qrSuffix=request.getParameter("qrSuffix");
        String qrcode=System.currentTimeMillis()+"."+qrSuffix;
        String path=qrcodePath+qrcode;
        boolean getQrcode=creatQrcode(qrData,path);
        if(getQrcode==true){
            ajaxResult.setState(true);
            ajaxResult.setData(qrcode);
        }
        return ajaxResult;
    }

    /**
     * 解析二维码
     * @return
     */
    @ResponseBody
    @PostMapping("/decoder.dd")
    public AjaxResult decoderQrcode(HttpServletRequest request){
        AjaxResult ajaxResult = new AjaxResult();
        ajaxResult.setState(false);
        String qrcode=request.getParameter("qrcode");

        String qrData=decoderQRCode(qrcodePath+qrcode);
        if(qrData!=null && !"".equals(qrData)){
            ajaxResult.setState(true);
            ajaxResult.setData(qrData);
        }
        return ajaxResult;
    }

}