Java 实现二维码生成与解析

得益于二维码的信息容量大、容错能力强、制作成本低等优点，在移动互联网时代，二维码得到了非常广泛的应用。

当然本篇文章并不是要讲二维码编码原理，想要了解原理可以看：https://coolshell.cn/articles/10590.html。本文主要讲应用层面，Java 中怎么生成和解析二维码。

二维码的生成和解析自然涉及到编码算法，这里我们引用 Google 的一个第三方包作为基础：

<!-- https://mvnrepository.com/artifact/com.google.zxing/core -->
<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>core</artifactId>
    <version>3.3.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.google.zxing/javase -->
<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>javase</artifactId>
    <version>3.3.0</version>
</dependency>

具体生成和解析方法：

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

import javax.imageio.ImageIO;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.DecodeHintType;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.Result;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
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.HybridBinarizer;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

/**
 * 二维码工具类 
 */
public class QRCodeUtils {
    
    /**
     * 生成二维码图片 
     * @param content 二维码内容 
     * @param size 图片大小 
     * @param outPath 图片输出路径 
     * @param onColor 前景色，默认黑色 
     * @param offColor 背景色， 默认白色 
     * @return
     */
    public static void generateQRCode(String content, int size, String outPath, Color onColor, Color offColor) throws Exception {
        File imageFile = new File(outPath);
        if (imageFile.exists()) {
            throw new RuntimeException("Image:" + outPath + "exist.");
        }
        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, StandardCharsets.UTF_8); // 内容编码 
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H); // 纠错级别 
        hints.put(EncodeHintType.MARGIN, 1); // 外边距 
        // 设置颜色（默认黑白）
        if (onColor == null) onColor = Color.BLACK;
        if (offColor == null) offColor = Color.WHITE;
        MatrixToImageConfig config = new MatrixToImageConfig(onColor.getRGB(), offColor.getRGB());
        BitMatrix bitMatrix = new MultiFormatWriter().encode(content, BarcodeFormat.QR_CODE, size, size, hints);
        MatrixToImageWriter.writeToPath(bitMatrix, "jpg", imageFile.toPath(), config);
    }
    
    /**
     * 解析二维码内容 
     * @param imageInputStream 图片输入流 
     * @return
     */
    public static String readQRCode(InputStream imageInputStream) throws Exception {
        if (imageInputStream == null) {
            throw new RuntimeException("Image inputStream is null.");
        }
        return readQRCode(ImageIO.read(imageInputStream));
    }
    
    /**
     * 解析二维码内容 
     * @param imageFile 二维码文件 
     * @return
     */
    public static String readQRCode(File imageFile) throws Exception {
        if (!imageFile.exists()) {
            throw new RuntimeException("Image not exist.");
        }
        return readQRCode(ImageIO.read(imageFile));
    }
    
    private static String readQRCode(BufferedImage image) throws Exception {
        Map<DecodeHintType, Object> hints = new HashMap();
        hints.put(DecodeHintType.CHARACTER_SET, StandardCharsets.UTF_8);
        BufferedImageLuminanceSource source = new BufferedImageLuminanceSource(image);
        BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
        Result result = new MultiFormatReader().decode(bitmap, hints);
        return result.getText();
    }
}

单元测试：

@Test
public void testQRCode() throws Exception {
    String path = "D:\\qrcode.jpg";
    // 生成 
    QRCodeUtils.generateQRCode("https://zhangzw.com/posts/20191203.html", 200, path, Color.BLUE, new Color(250, 250, 250));
    // 解析 
    String content = QRCodeUtils.readQRCode(new FileInputStream(path));
    System.out.println("解析二维码：" + content);
}
// out: 解析二维码：https://zhangzw.com/posts/20191203.html

生成效果：