easyexcel實作匯出添加文字水印

引入jar包

由于easyexcel沒有引入ooxml-schemas包，所以需要額外添加，

<!-- easyexcel依賴 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>2.2.6</version>
</dependency>
<!-- poi 添加水印 -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>ooxml-schemas</artifactId>
    <version>1.4</version>
</dependency>
<!-- 使用了hutool的工具類 -->
<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
</dependency>

新增水印配置類和WriteHandler

新增水印配置類

@Data
public class Watermark {

    /**
     * 水印內容
     */
    private String content = "";

    /**
     * 畫筆顏色. eg:#C5CBCF
     */
    private String color = "#C5CBCF";

    /**
     * 字體顏色
     */
    private Font font = new Font("microsoft-yahei", Font.PLAIN, 20);

    /**
     * 水印寬、高
     */
    private int width = 300;
    private int height = 100;

    /**
     * 傾斜度
     */
    private double shear1 = 0.1;
    private double shear2 = -0.26;

    /**
     * 字體的y軸位置
     */
    private int yAxis = 50;

}

新增WriteHandler

注意：此方法只適用于XSSFWorkbook類，easyexcel默認使用的是SXSSFWorkbook類，在使用easyexcel匯出時需要設定為inMemory模式，否則會拋出型別轉換例外，

public class CustomWaterMarkHandler implements SheetWriteHandler {

    private final Watermark watermark;

    public CustomWaterMarkHandler(Watermark watermark) {
        this.watermark = watermark;
    }

    @Override
    public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {

    }

    @Override
    public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
        try {
            BufferedImage bufferedImage = createWatermarkImage();
            setWaterMarkToExcel((XSSFWorkbook) writeWorkbookHolder.getWorkbook(), bufferedImage);
        } catch (Exception e) {
            throw new RuntimeException("添加水印出錯");
        }
    }

    private BufferedImage createWatermarkImage() {
        final Font font = watermark.getFont();
        final int width = watermark.getWidth();
        final int height = watermark.getHeight();

        String[] textArray = watermark.getContent().split(",");
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 背景透明 開始
        Graphics2D g = image.createGraphics();
        image = g.getDeviceConfiguration().createCompatibleImage(width, height, Transparency.TRANSLUCENT);
        g.dispose();
        // 背景透明 結束
        g = image.createGraphics();
        // 設定畫筆顏色
        g.setColor(new Color(Integer.parseInt(watermark.getColor().substring(1), 16)));
        // 設定畫筆字體
        g.setFont(font);
        // 設定傾斜度
        g.shear(watermark.getShear1(), watermark.getShear2());

        // 設定字體平滑
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        int y = watermark.getYAxis();
        for (String s : textArray) {
            // 從畫框的y軸開始畫字串.假設電腦螢屏中心為0，y軸為正數則在下方
            g.drawString(s, 0, y);
            y = y + font.getSize();
        }

        // 釋放畫筆
        g.dispose();
        return image;
    }

    private void setWaterMarkToExcel(XSSFWorkbook workbook, BufferedImage bfi) {
        //將圖片添加到作業簿
        int pictureIdx = workbook.addPicture(ImgUtil.toBytes(bfi, ImgUtil.IMAGE_TYPE_PNG), Workbook.PICTURE_TYPE_PNG);
        //建立 sheet 和 圖片 的關聯關系
        XSSFPictureData xssfPictureData = https://www.cnblogs.com/yywf/p/workbook.getAllPictures().get(pictureIdx);
        for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
            XSSFSheet xssfSheet = workbook.getSheetAt(i);
            PackagePartName packagePartName = xssfPictureData.getPackagePart().getPartName();
            PackageRelationship packageRelationship = xssfSheet.getPackagePart()
                    .addRelationship(packagePartName, TargetMode.INTERNAL, XSSFRelation.IMAGES.getRelation(), null);
            //添加水印到作業表
            xssfSheet.getCTWorksheet().addNewPicture().setId(packageRelationship.getId());
        }
    }
}

測驗

//水印配置
Watermark watermark = new Watermark();
watermark.setContent("測驗文字水印");
watermark.setWidth(500);
watermark.setHeight(200);
watermark.setYAxis(200);

//匯出
EasyExcel.write(outputStream, Test.class)
        .inMemory(true)
        .sheet("sheet1")
        .registerWriteHandler(new CustomWaterMarkHandler(watermark))
        .doWrite(Collections.singletonList(new Test()));

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