Java 多个条形码生成，返回前台预览，并可选打印机打印

您可以使用一些 Java 的条形码生成库（如Zxing、Barbecue等）来生成多个条形码图片，并将这些图片返回给前台进行预览和打印。以下是一个简单的实现示例：

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

@Controller
@RequestMapping("/barcode")
public class BarcodeController {

    @GetMapping("/generate")
    @ResponseBody
    public List<String> generateBarcodes(@RequestParam("data") List<String> data,
                                         HttpServletResponse response) throws IOException {
        List<String> barcodeUrls = new ArrayList<>();
        for (String d : data) {
            // 生成条形码
            BufferedImage barcodeImage = generateBarcode(d);
            // 将图片转换为BASE64编码字符串
            String barcodeUrl = imageToBase64(barcodeImage);
            barcodeUrls.add(barcodeUrl);
        }
        return barcodeUrls;
    }

    private BufferedImage generateBarcode(String data) {
        int width = 300;
        int height = 100;
        String format = "png";
        BarcodeFormat barcodeFormat = BarcodeFormat.CODE_128;
        ErrorCorrectionLevel errorCorrectionLevel = ErrorCorrectionLevel.L;
        // 设置条形码参数
        com.google.zxing.EncodeHintType hintType = EncodeHintType.ERROR_CORRECTION;
        com.google.zxing.EncodeHintType encodingType = EncodeHintType.CHARACTER_SET;
        com.google.zxing.EncodeHintType marginType = EncodeHintType.MARGIN;
        int margin = 2;
        java.util.Map<com.google.zxing.EncodeHintType, Object> hints = new java.util.HashMap<>();
        hints.put(hintType, errorCorrectionLevel);
        hints.put(encodingType, "UTF-8");
        hints.put(marginType, margin);

        BitMatrix bitMatrix = null;
        try {
            bitMatrix = new com.google.zxing.MultiFormatWriter().encode(data, barcodeFormat, width, height, hints);
        } catch (WriterException e) {
            e.printStackTrace();
        }
        BufferedImage image = MatrixToImageWriter.toBufferedImage(bitMatrix);
        return image;
    }

    private String imageToBase64(BufferedImage image) throws IOException {
        String base64 = null;
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        try {
            ImageIO.write(image, "png", outputStream);
            byte[] bytes = outputStream.toByteArray();
            base64 = java.util.Base64.getEncoder().encodeToString(bytes);
        } finally {
            outputStream.close();
        }
        return base64;
    }
}

在上面的示例中，我们使用了Zxing库生成条形码，将生成的条形码图片转换为BASE64编码字符串，并将多个条形码的URL返回给前台。您可以使用JavaScript等前端工具将这些URL转换为图片进行预览和打印。