SpringBoot实现PPT格式文件上传并在线预览功能

1、需要引入依赖

<dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.9</version>
        </dependency>
         <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.15</version>
        </dependency>
               <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.15</version>
        </dependency>
        <!--其他格式转换为PDF -->
        <dependency>
            <groupId>fr.opensagres.xdocreport</groupId>
            <artifactId>xdocreport</artifactId>
            <version>1.0.6</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.11.0</version>
        </dependency>

2、上传文件到本地文件夹中

 @PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public ResponseEntity<Object> uploadFileToLocal(@RequestParam("multipartFile") MultipartFile multipartFile) {
        if (multipartFile == null) {
            return ResponseEntity.status(HttpStatus.NO_CONTENT).build();
        }
        File file = null;
        try {
            File dir = new File(basePath);
            if (!dir.exists()) {
                dir.mkdir();
            }
            file = new File(basePath + File.separator + multipartFile.getOriginalFilename());
            if (!file.exists()) {
                multipartFile.transferTo(file);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return ResponseEntity.ok(FileVo.builder().size(multipartFile.getSize()).path(file.getAbsolutePath()).build());

    }

basePath为定义的常量： private static final String basePath = “C:\tempFile”;

通过上传接口，可在C盘的tempfile目录下找到上传的文件，首先我们先上传一个PPT文件，上传成功会返回文件的绝对路径地址以及文件大小，绝对地址将作为在线预览文件接口的参数。

3、在线预览PPT文件

 @GetMapping("/showPPT")
    public void showPPT(@RequestParam("path") String path,HttpServletResponse response) throws IOException {
        byte[] buffer = new byte[1024 * 4];
        String type = path.substring(path.lastIndexOf(".") + 1);
        //转换pdf文件,如存在则直接显示pdf文件
        String pdf = path.replace(type, "pdf");
        File pdfFile = new File(pdf);
        if (pdfFile.exists()) {
            outFile(buffer, pdfFile, response);
        } else {
            FileInputStream in = new FileInputStream(path);
            ZipSecureFile.setMinInflateRatio(-1.0d);
            XMLSlideShow xmlSlideShow = new XMLSlideShow(in);
            in.close();
            // 获取大小
            Dimension pgsize = xmlSlideShow.getPageSize();
            // 获取幻灯片
            List<XSLFSlide> slides = xmlSlideShow.getSlides();
            List<File> imageList = new ArrayList<>();
            for (int i = 0; i < slides.size(); i++) {
                // 解决乱码问题
                List<XSLFShape> shapes = slides.get(i).getShapes();
                for (XSLFShape shape : shapes) {
                    if (shape instanceof XSLFTextShape) {
                        XSLFTextShape sh = (XSLFTextShape) shape;
                        List<XSLFTextParagraph> textParagraphs = sh.getTextParagraphs();
                        for (XSLFTextParagraph xslfTextParagraph : textParagraphs) {
                            List<XSLFTextRun> textRuns = xslfTextParagraph.getTextRuns();
                            for (XSLFTextRun xslfTextRun : textRuns) {
                                xslfTextRun.setFontFamily("宋体");
                            }
                        }
                    }
                }
                //根据幻灯片大小生成图片
                BufferedImage img = new BufferedImage(pgsize.width, pgsize.height, BufferedImage.TYPE_INT_RGB);
                Graphics2D graphics = img.createGraphics();
                graphics.setPaint(Color.white);
                graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));
                // 将PPT内容绘制到img上
                slides.get(i).draw(graphics);
                //图片将要存放的路径
                String absolutePath = basePath + File.separator+ (i + 1) + ".jpg";
                File jpegFile = new File(absolutePath);
                if (!jpegFile.exists()) {
                    // 判断如果图片存在则不再重复创建，建议将图片存放到一个特定目录，后面会统一删除
                    FileOutputStream fileOutputStream = new FileOutputStream(jpegFile);
                    ImageIO.write(img, "jpg", fileOutputStream);
                }
                // 图片路径存放
                imageList.add(jpegFile);
            }
            File file = png2Pdf(imageList, pdf);
            outFile(buffer, file, response);
        }
    }

    private void outFile(byte[] buffer, File pdfFile, HttpServletResponse response) throws IOException {
        ByteArrayOutputStream out;
        int n = 0;
        FileInputStream fileInputStream = new FileInputStream(pdfFile);
        out = new ByteArrayOutputStream();
        ServletOutputStream outputStream = response.getOutputStream();
        while ((n = fileInputStream.read(buffer)) != -1) {
            out.write(buffer, 0, n);
        }
        outputStream.write(out.toByteArray());
        outputStream.flush();
    }
	//将图片列表转换为PDF格式文件并存储
    public File png2Pdf(List<File> pngFiles, String pdfFilePath) {
        Document document = new Document();
        File pdfFile = null;
        long startTime = System.currentTimeMillis();
        try {
            pdfFile = new File(pdfFilePath);
            if (pdfFile.exists()) {
                return pdfFile;
            }
            PdfWriter.getInstance(document, new FileOutputStream(pdfFile));
            document.open();
            pngFiles.forEach(pngFile -> {
                try {
                    Image png = Image.getInstance(pngFile.getCanonicalPath());
                    png.scalePercent(50);
                    document.add(png);
                } catch (Exception e) {
                    System.out.println("png2Pdf exception");
                }
            });
            document.close();
            return pdfFile;
        } catch (Exception e) {
            System.out.println(String.format("png2Pdf %s exception", pdfFilePath));
        } finally {
            if (document.isOpen()) {
                document.close();
            }
            // 删除临时生成的png图片
            for (File pngFile : pngFiles) {
                try {
                    FileUtils.delete(pngFile);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            long endTime = System.currentTimeMillis();
            System.out.println("png2Pdf耗时：" + (endTime - startTime));
        }

        return null;
    }

核心思路：将PPT文件读取每一页幻灯片，将幻灯片转换为图片格式，最后将所有图片放到一个pdf文件中形成一个pdf文件用于在线预览。预览时会在同级目录下创建一个相同文件名后缀为pdf的文件，每次预览会先查找文件是否存在，存在则直接预览，不存在则会走上面的处理。

4、预览效果

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