SSM生成二维码保存到数据库中

可以使用zxing库生成二维码，再将二维码图片转化为字节数组，存入数据库中。

下面给出一个简单的示例代码：

1. 添加依赖

在pom.xml中添加以下依赖：

<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>core</artifactId>
    <version>3.4.0</version>
</dependency>
<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>javase</artifactId>
    <version>3.4.0</version>
</dependency>

2. 编写生成二维码的方法

public static byte[] generateQRCode(String content) throws WriterException, IOException {
    int width = 200; // 二维码图片宽度
    int height = 200; // 二维码图片高度

    // 设置二维码参数
    Map<EncodeHintType, Object> hints = new HashMap<>();
    hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
    hints.put(EncodeHintType.MARGIN, 1);

    // 生成二维码
    BitMatrix bitMatrix = new MultiFormatWriter().encode(content, BarcodeFormat.QR_CODE, width, height, hints);

    // 将BitMatrix转换为BufferedImage
    BufferedImage image = MatrixToImageWriter.toBufferedImage(bitMatrix);

    // 将BufferedImage转换为字节数组
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    ImageIO.write(image, "png", outputStream);
    byte[] bytes = outputStream.toByteArray();

    return bytes;
}

3. 在Controller中调用方法并保存到数据库

@Controller
public class QRCodeController {

    @Autowired
    private QRCodeService qrCodeService;

    @RequestMapping("/generateQRCode")
    public String generateQRCode(Model model, @RequestParam String content) {
        try {
            byte[] bytes = QRCodeUtil.generateQRCode(content);
            qrCodeService.saveQRCode(bytes);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "success";
    }
}

@Service
public class QRCodeServiceImpl implements QRCodeService {

    @Autowired
    private QRCodeMapper qrCodeMapper;

    @Override
    public void saveQRCode(byte[] bytes) {
        QRCode qrCode = new QRCode();
        qrCode.setBytes(bytes);
        qrCodeMapper.insert(qrCode);
    }
}

4. 在页面中显示二维码

在页面中使用img标签，并将src属性设置为一个servlet或controller的路径，通过读取数据库中的二维码字节数组生成二维码图片并显示。

<img src="${pageContext.request.contextPath}/showQRCode?id=${qrCode.id}">

@Controller
public class QRCodeController {

    @Autowired
    private QRCodeService qrCodeService;

    @GetMapping("/showQRCode")
    public void showQRCode(HttpServletRequest request, HttpServletResponse response, Long id) {
        try {
            QRCode qrCode = qrCodeService.getQRCodeById(id);
            byte[] bytes = qrCode.getBytes();
            response.setContentType("image/png");
            ServletOutputStream outputStream = response.getOutputStream();
            outputStream.write(bytes);
            outputStream.flush();
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public interface QRCodeMapper {
    void insert(QRCode qrCode);

    QRCode selectById(Long id);
}

public class QRCode {
    private Long id;
    private byte[] bytes;

    // getter/setter方法
}