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java项目文件水印功能实现

java项目文件水印功能实现

Posted by John Doe on 2024-10-09
Words 1.6k and Reading Time 7 Minutes
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背景

需求要求实现pdf,word,png,jpg等格式文件添加水印并下载的功能，采用了策略模式易于扩展，特此记录实现方式。

下载实现

常见的input、output流实现，这里以mongoDB获取输入流为例

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@Autowired
private GridFSBucket gridFSBucket;

@Autowired
private GridFsTemplate gridFsTemplate;

@Autowired
private List<WatermarkService> watermarkServiceList;


public void fileDownload(String fileId, HttpServletResponse response, HttpServletRequest request, String watermark) {
    try {
        DocumentDesc documentDesc= DBDao.getFile(fileId);

        // 从mongoDB获取文件流
        Query query = Query.query(Criteria.where("_id").is(documentDesc.getDocStorePath()));
        GridFSFile gridFSFile = gridFsTemplate.findOne(query);
        GridFSDownloadStream gridFSDownloadStream = gridFSBucket.openDownloadStream(gridFSFile.getObjectId());
        GridFsResource gridFsResource = new GridFsResource(gridFSFile, gridFSDownloadStream);
        InputStream inputStream = gridFsResource.getInputStream();
        
        // 获取文件类型
        String[] split = documentDesc.getFileName().split("\\.");
        String fileType = split[split.length - 1];
        
        // 策略模式根据不同的文件类型下载文件
        WatermarkService watermarkService = watermarkServiceList.stream().filter(o -> o.support(fileType)).findAny().orElse(null);
        
        OutputStream sos = response.getOutputStream();
        String name = documentDesc.getFileName();
        response.setContentType("application/octet-stream;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");
        // 设置下载文件名
        String fileName = URLEncoder.encode(name, "UTF-8").replaceAll("\\+", "%20");
        // 设置下载文件名
        response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        watermarkService.add(inputStream, sos, watermark);
        // 向客户端输出文件
        IOUtils.copy(inputStream, sos);
        sos.flush();
        sos.close();
        logger.info("fileId {} success ", fileId);
    } catch (Exception e) {
        log.error("下载文件失败：", e);
        throw new BizException("下载文件失败");
    }
}

使用策略模式划分功能

使用策略模式可以更方便的扩展功能，增强代码可读性维护性，避免过多的if-else判断。

模板接口

后续的各种类型文件需实现该接口

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public interface WatermarkService {

    boolean support(String type);

    OutputStream add(InputStream inputStream, OutputStream outputStream, String text) throws Exception;

}

使用stream流优雅分类

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@Autowired
private List<WatermarkService> watermarkServiceList;

// 文件后缀名满足support方法的service会被过滤出来，后续调用add()方法即可添加对应文件类型的水印
WatermarkService watermarkService = watermarkServiceList.stream().filter(o -> o.support(fileType)).findAny().orElse(null);

...
// 调用add()方法添加水印    
watermarkService.add(inputStream, sos, watermark);

各种文件类型的具体实现方式

多数水印功能的实现的通过创建一个图片文件，然后将该图片文件添加到指定的pdf、word、excel文件上，下面是自定义图片类的代码，包含图片的存储地址，长和宽。

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@Getter
@AllArgsConstructor
public static class ImageMessage {
    private int width;
    private int height;
    private String filePath;
}

1.pdf

这里使用的是apache.pdfbox.pdmodel.PDDocument包进行pdf操作, 具体实现步骤为:1.获取文件流。2.创建需要添加的水印图片样式。3.将创建好的水印图片添加到pdf上

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import org.apache.pdfbox.pdmodel.PDDocument;

@Slf4j
@Service
public class PdfWatermarkServiceImpl implements WatermarkService {

    @Override
    public boolean support(String type) {
        return StringUtils.equalsIgnoreCase("PDF", type);
    }


    @Override
    public OutputStream add(InputStream inputStream, OutputStream outputStream, String text) throws IOException {
        if (ignore(text)) return outputStream;
        try {
            PDDocument doc = PDDocument.load(inputStream);
            // 移除pdf加密策略，否则可能获取pdf文件失败
            doc.setAllSecurityToBeRemoved(true);
            
            // 计算对角线长度，参考Math.sqrt(width * width + height * height)
            Double diagonal = getDiagonal(doc);
            
            // 1.1创建水印图片
            ImageGeneratorUtil.ImageMessage image = getImage(text, diagonal);
            
            // 1.2将水印图片添加到pdf文件上，具体实现见下文
            PdfWatermarkUtil.addSingleDiagonalWaterMarkToPdf(doc, image, outputStream);
            
        }  catch (Exception e) {
            log.error("exception message ", e);
        }
        return outputStream;
    }
    
    // 1.1 绘制水印图片，下面代码是示例代码，具体的水印文本重复次数、字体格式、偏转角度请自行计算
        public static ImageMessage getImage(String text, Double maxWidth) throws IOException {
        BufferedImage image = generateTransparentImage(text, maxWidth);
        ......
        return new ImageMessage(image.getWidth(), image.getHeight(), pathname.toAbsolutePath().toString());
    }
    
    
    public static BufferedImage generateTransparentImage(String text, double diagonalLength) {
        // 初始字体大小
        float fontSize = 8.0f;
        Font font;
        // 预留一部分对角线长度
        diagonalLength = 0.8f * diagonalLength;

        BufferedImage image = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = image.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        FontRenderContext frc = g2d.getFontRenderContext();
        Rectangle2D bounds;
        double currentDiagonal;
        int width = 0, height = 0; // 在循环外部声明 width 和 height
        font = FontLoaderUtil.getFont(fontSize);
        
        //todo 使用对应的字体格式
        
        g2d.dispose();

        // 使用找到的字体大小和计算出的 width 和 height 重新创建图像
        image = new BufferedImage(width + 20, height, BufferedImage.TYPE_INT_ARGB);
        g2d = image.createGraphics();
        setGraphicsHints(g2d);
        g2d.setFont(font);
        drawText(g2d, text, width, height, frc); // 确保 drawText 方法可以访问到正确的 width 和 height

        g2d.dispose();
        return image;
    }
    
    
    
    // 1.2 向PDF添加水印图片
        public static void addSingleDiagonalWaterMarkToPdf(PDDocument doc, ImageGeneratorUtil.ImageMessage img, OutputStream outputStream) throws IOException {
        try {
            // 移除所有安全设置，包括加密
            doc.setAllSecurityToBeRemoved(true);

            // 获取水印图片
            PDImageXObject pdImage = PDImageXObject.createFromFile(img.getFilePath(), doc);
            
            //对水印图片进行翻转等操作，比如斜着的文字水印
            WatermarkOptions options = new WatermarkOptions()
                    .size(img.getWidth(), img.getHeight())
                    .padding(10)
                    .layout(4, 3)
                    .rotate(30);

            // for循环每一页添加水印图片
            for (PDPage page : doc.getPages()) {
                addSingleDiagonalWaterMarkToPdf(doc, page, pdImage, options);
            }
            doc.save(outputStream);
        } finally {
            // 删除水印图片
            boolean delete = new File(img.getFilePath()).delete();
        }

    }

}

2.png,jpg,jpeg

接口实现

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@Slf4j
@Service
public class ImageWatermarkServiceImpl implements WatermarkService {
    @Override
    public boolean support(String type) {
        return StringUtils.equalsAnyIgnoreCase(type, "PNG", "JPG", "JPEG");
    }

    @Override
    public OutputStream add(InputStream inputStream, OutputStream outputStream, String text) throws IOException {
        if (ignore(text)) return outputStream;
        try {
            // 水印字体颜色
            PictureWatermarkUtil waterMarker = new PictureWatermarkUtil(text);
            ImageIO.write(makeBottomRightWaterMark(inputStream), "PNG", outputStream)
        } catch (Exception e) {
            log.error("图片添加水印并下载失败");
        }
        return outputStream;
    }
    
    /**
     * 在指定图片右下角添加上文本水印
     *
     * @param inputStream 需要加水印图片的输入流（不会修改原图）
     * @return 添加水印后的图片对象
     */
    public BufferedImage makeBottomRightWaterMark(InputStream inputStream) throws IOException {
        BufferedImage originalImage = ImageIO.read(inputStream);
        BufferedImage bufferedImage = new BufferedImage(originalImage.getWidth(), originalImage.getHeight(), originalImage.getType());
        Graphics2D g2 = bufferedImage.createGraphics(); // 获取图片画布
        // 文本抗锯齿
        g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g2.setFont(waterMarkFont); // 设置字体
        g2.setPaint(waterMarkPaint); // 设置字体颜色
        g2.drawImage(originalImage, 0, 0, null);
        int hoffset = 20; // 水平方向与最右的偏移量
        int voffset = 20; // 垂直方向与最低端的偏移量
        g2.drawString(customText,
                bufferedImage.getWidth() - getTextLength(g2, customText) - hoffset,
                bufferedImage.getHeight() - voffset);
        g2.dispose();
        return bufferedImage;
    }    
        
}

3.word

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@Slf4j
@Service
public class WordWatermarkServiceImpl implements WatermarkService {
    @Override
    public boolean support(String type) {
        return StringUtils.equalsIgnoreCase("DOCX", type);
    }

    @Override
    public OutputStream add(InputStream inputStream, OutputStream outputStream, String text) throws IOException {
        if (ignore(text)) return outputStream;
        try {
            // todo业务自定义代码，如字体透明度要求等具体实现
            // 添加水印
            makeSlopeWaterMark(inputStream, outputStream);
            IOUtils.copy(inputStream, outputStream);
        } catch (Exception e) {
            log.error("exception message ", e);
        }
        return outputStream;
    }
    
/**
     * 【核心方法】将输入流中的docx文档加载添加水印后输出到输出流中.
     *
     * @param inputStream  docx文档输入流
     * @param outputStream 添加水印后docx文档的输出流
     */
    public void makeSlopeWaterMark(InputStream inputStream, OutputStream outputStream) {
        Path tempFile = createTempFile(inputStream);
        if (tempFile == null) {
            return;
        }
        try (BufferedInputStream buffIn = new BufferedInputStream(Files.newInputStream(tempFile))) {
            XWPFDocument doc = loadDocXDocument(buffIn, outputStream);
            if (doc == null) {
                return;
            }
            // 遍历文档，添加水印
            for (int lineIndex = -10; lineIndex < 10; lineIndex++) {
                //到顶部距离
                styleTop = 200 * lineIndex + " ";
                waterMarkDocXDocument(doc);
            }
            try {
                doc.write(outputStream); // 写出添加水印后的文档
            } finally {
                IOUtils.closeQuietly(doc);
            }
        } catch (Exception exception) {
            throw new RuntimeException("水印添加失败！");
        } finally {
            deleteFile(tempFile);
        }
    }
}

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