Java实现Excel导出并添加水印

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-compress</artifactId>
            <version>1.22</version>
        </dependency>
        <!-- Apache POI for Excel -->
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>5.2.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>5.2.3</version>
        </dependency>
        <!-- Apache POI dependencies -->
        <dependency>
            <groupId>org.apache.xmlbeans</groupId>
            <artifactId>xmlbeans</artifactId>
            <version>5.1.1</version>
        </dependency>

public static ByteArrayOutputStream createWaterMark(String content)
            throws IOException {
        // 这是水印字体的宽和高，可以调整这个大小来控制
        int width = 200;
        int height = 150;
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);// 获取bufferedImage对象
        String fontType = "微软雅黑";
        int fontStyle = Font.BOLD;
        // 这是水印显示字体的大小
        int fontSize = 20;
        Font font = new Font(fontType, fontStyle, fontSize);
        Graphics2D g2d = image.createGraphics(); // 获取Graphics2d对象
        image = g2d.getDeviceConfiguration().createCompatibleImage(width,
                height, Transparency.TRANSLUCENT);
        g2d.dispose();
        g2d = image.createGraphics();
        g2d.setColor(new Color(0, 0, 0, 20)); // 设置字体颜色和透明度，最后一个参数为透明度
        g2d.setStroke(new BasicStroke(1)); // 设置字体
        g2d.setFont(font); // 设置字体类型 加粗 大小
        g2d.rotate(-0.5, (double) image.getWidth() / 2,
                (double) image.getHeight() / 2);// 设置倾斜度
        FontRenderContext context = g2d.getFontRenderContext();
        Rectangle2D bounds = font.getStringBounds(content, context);
        double x = (width - bounds.getWidth()) / 2;
        double y = (height - bounds.getHeight()) / 2;
        double ascent = -bounds.getY();
        double baseY = y + ascent;
        // 写入水印文字原定高度过小，所以累计写水印，增加高度
        g2d.drawString(content, (int) x, (int) baseY);
        // 设置透明度
        g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
        // 释放对象
        g2d.dispose();
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        ImageIO.write(image, "png", os);
        return os;
    }

    public static void main(String[] args) throws IOException {
        XSSFWorkbook workbook = new XSSFWorkbook();
        XSSFSheet sheet = workbook.createSheet("Sheet1");
        ByteArrayOutputStream byteArrayOutputStream = createWaterMark("水印内容");
        int pictureIdx = workbook.addPicture(byteArrayOutputStream.toByteArray()
                ,Workbook.PICTURE_TYPE_PNG);
        String rID = sheet.addRelation(null, XSSFRelation.IMAGES,workbook
                .getAllPictures().get(pictureIdx)).getRelationship().getId();
        sheet.getCTWorksheet().addNewPicture().setId(rID);

        // 创建一个行对象
        XSSFRow row = sheet.createRow(0);  // 第一行

        // 在行中创建单元格并设置值
        XSSFCell cell = row.createCell(0); // 第一列
        cell.setCellValue("Hello, Excel!");

        // 写入到文件系统
        try (FileOutputStream outputStream = new FileOutputStream("Example.xlsx")) {
            workbook.write(outputStream);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                workbook.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }