Java自定义打印机打印条形码

要在Java自定义打印机中打印条形码，可以使用第三方库，例如Zxing。下面是一个示例代码：

import javax.print.*;
import javax.print.attribute.HashPrintRequestAttributeSet;
import javax.print.attribute.PrintRequestAttributeSet;
import javax.print.attribute.standard.Copies;
import javax.print.attribute.standard.MediaPrintableArea;
import javax.print.attribute.standard.MediaSizeName;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.oned.Code128Writer;
import com.google.zxing.client.j2se.MatrixToImageWriter;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.print.PrinterJob;
import java.awt.image.BufferedImage;
import java.io.IOException;

public class CustomPrinter implements Printable {

    @Override
    public int print(Graphics graphics, PageFormat pageFormat, int pageIndex) throws PrinterException {
        if (pageIndex > 0) {
            return Printable.NO_SUCH_PAGE;
        }

        // 绘制打印内容
        Graphics2D g2d = (Graphics2D) graphics;
        g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());

        // 生成条形码
        Code128Writer writer = new Code128Writer();
        BitMatrix matrix = writer.encode("123456789", BarcodeFormat.CODE_128, 200, 100);
        BufferedImage image = MatrixToImageWriter.toBufferedImage(matrix);

        // 绘制条形码
        g2d.drawImage(image, 0, 0, null);

        return Printable.PAGE_EXISTS;
    }

    public static void main(String[] args) {
        // 获取默认打印机
        PrinterJob printerJob = PrinterJob.getPrinterJob();
        PrintService printService = printerJob.getPrintService();

        // 设置打印参数
        PrintRequestAttributeSet printRequestAttributeSet = new HashPrintRequestAttributeSet();
        printRequestAttributeSet.add(new Copies(1));
        printRequestAttributeSet.add(new MediaPrintableArea(0,0,200,100,MediaPrintableArea.MM));
        printRequestAttributeSet.add(MediaSizeName.ISO_A4);

        // 设置打印内容
        CustomPrinter customPrinter = new CustomPrinter();

        // 开始打印
        try {
            printerJob.setPrintService(printService);
            printerJob.setPrintable(customPrinter);
            printerJob.print(printRequestAttributeSet);

        } catch (PrinterException e) {
            e.printStackTrace();
        }
    }
}

这个示例代码使用Code128Writer和MatrixToImageWriter类生成一个条形码，并将其绘制在打印页面上。你可以根据自己的需要修改条形码内容和打印参数来自定义打印机。