SpringBoot中生成二维码的案例实战

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在Spring Boot项目中整合ZXing库来生成二维码是一个常见的需求。

zxing，全称"Zebra Crossing"，是一个功能强大的开源Java库，专门用于二维码的生成与解析。它不仅能够生成QR码，还能解析包括QR码在内的多种二维码格式。ZXing提供了多语言API，使得开发者能够轻松地将二维码功能集成到各种应用中。它支持Android、iOS、Java等多个平台，并且除了QR码，还能解析其他一维码和二维码，如EAN、UPC、DataMatrix等。

1. 添加zxing库的依赖

<dependency>
    <groupId>com.google.zxinggroupId>
    <artifactId>coreartifactId>
    <version>3.5.2version>
dependency>
<dependency>
    <groupId>com.google.zxinggroupId>
    <artifactId>javaseartifactId>
    <version>3.5.2version>
dependency>

2. 生成二维码

创建一个SpringBoot服务类QRCodeService，用于生成二维码图片：

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;

@Service
public class QRCodeService {

    public void generateQRCodeImage(String text, int width, int height, String filePath)
            throws IOException {
        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);
        hints.put(EncodeHintType.MARGIN, 2);

        BitMatrix bitMatrix = new MultiFormatWriter().encode(text, BarcodeFormat.QR_CODE, width, height, hints);

        Path path = FileSystems.getDefault().getPath(filePath);
        MatrixToImageWriter.writeToPath(bitMatrix, "PNG", path);
    }
}

3. 调用二维码服务

3.1 将二维码图拍你保存

最后在SpringBoot的Controller中调用这个服务：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;

@RestController
public class QRCodeController {

    @Autowired
    private QRCodeService qrCodeService;

    @GetMapping("/generateQRCode")
    public String generateQRCode(@RequestParam String text, @RequestParam int width, @RequestParam int height) {
        try {
            qrCodeService.generateQRCodeImage(text, width, height, "myqrcode.png");
            return "QR Code generated successfully!";
        } catch (IOException e) {
            return "QR Code generation failed: " + e.getMessage();
        }
    }
}

当访问/generateQRCode端点并传递text、width和height参数时，它将生成一个名为myqrcode.png的二维码图片并保存到项目根目录下。

http://localhost:8080/generateQRCode?text=Hello,World!&width=350&height=350

3.2. 直接返回二维码图片

修改QRCodeController来返回二维码图片：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import javax.imageio.ImageIO;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

@RestController
public class QRCodeController {

    @GetMapping("/generateQRCode")
    public ResponseEntity<Resource> generateQRCode(@RequestParam String text, @RequestParam Integer width, @RequestParam Integer  height) throws IOException {
        BitMatrix bitMatrix = new MultiFormatWriter().encode(text, BarcodeFormat.QR_CODE, width, height, getHints());

        BufferedImage qrCodeImage = MatrixToImageWriter.toBufferedImage(bitMatrix);
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ImageIO.write(qrCodeImage, "PNG", byteArrayOutputStream);

        byte[] qrCodeBytes = byteArrayOutputStream.toByteArray();

        HttpHeaders headers = new HttpHeaders();
        headers.add(HttpHeaders.CONTENT_TYPE, MediaType.IMAGE_PNG_VALUE);

        return ResponseEntity.ok()
                .headers(headers)
                .contentLength(qrCodeBytes.length)
                .body(new ByteArrayResource(qrCodeBytes));
    }

    private Map<EncodeHintType, Object> getHints() {
        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);
        hints.put(EncodeHintType.MARGIN, 2);
        return hints;
    }
}

generateQRCode先生成二维码的BitMatrix，然后转换为BufferedImage，以便获取二维码图片的字节流。

3.2 注册BufferedImage消息转换器返回图片

3.2中返回图片也可以通过注册一个SpringBoot的消息转换器来实现:

@Bean
 public HttpMessageConverter<BufferedImage> createImageHttpMessageConverter() {
  return new BufferedImageHttpMessageConverter();
 }

返回图片

package com.example.demo.controller;

import java.awt.image.BufferedImage;

import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;

@RestController
@RequestMapping("/qr")
public class QrCodeController {

 @GetMapping(value = "/{barcode}", produces = MediaType.IMAGE_PNG_VALUE)
 public ResponseEntity<BufferedImage> barbecueEAN13Barcode(@PathVariable("barcode") String barcode)
   throws Exception {

  QRCodeWriter barcodeWriter = new QRCodeWriter();
     BitMatrix bitMatrix = 
       barcodeWriter.encode(barcode, BarcodeFormat.QR_CODE, 200, 200);

  return new ResponseEntity<>(MatrixToImageWriter.toBufferedImage(bitMatrix),HttpStatus.OK);
 }

}

现在，当访问/qr端点时，将直接收到一个二维码图片作为响应。

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