预览存储在mongoDB的文件（excel、word、PDF、图片）

@RequestMapping(value = "/preview")    public void preview(String attachmentId) {//获取存储在mongodb文件对应的idAttachment attachment = attachmentService.getAttachmentDetail(attachmentId);        GridFSDBFile gridFSDBFile = attachmentService.getGridFSDBFile(attachment.getDbStoreId());             try { //1、EXCEL（转换为HTML预览）                HSSFWorkbook workBook = new HSSFWorkbook(gridFSDBFile.getInputStream());                ExcelToHtmlConverter converter = new ExcelToHtmlConverter(DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument());                converter.setOutputColumnHeaders(false);// 不显示列的表头                converter.setOutputRowNumbers(false);// 不显示行的表头                converter.processWorkbook(workBook);                ByteArrayOutputStream outStream = new ByteArrayOutputStream();                StreamResult streamResult = new StreamResult(outStream);                Transformer serializer = TransformerFactory.newInstance().newTransformer();                serializer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");                serializer.setOutputProperty(OutputKeys.INDENT, "yes");                serializer.setOutputProperty(OutputKeys.METHOD, "html");                serializer.transform(new DOMSource(converter.getDocument()),                        streamResult);                response.getOutputStream().write(outStream.toByteArray());                        //2、word（转换为HTML预览）            HWPFDocument wordDocument = new HWPFDocument(gridFSDBFile.getInputStream());            WordToHtmlConverter wordToHtmlConverter = new WordToHtmlConverter(                    DocumentBuilderFactory.newInstance().newDocumentBuilder()                            .newDocument());            wordToHtmlConverter.setPicturesManager(new PicturesManager() {                public String savePicture(byte[] content, PictureType pictureType,                                          String suggestedName, float widthInches, float heightInches) {                    return "E:/test/"+suggestedName;                }            });            List pics = wordDocument.getPicturesTable().getAllPictures();            if (pics != null) {                for (int i = 0; i < pics.size(); i++) {                    Picture pic = (Picture) pics.get(i);                    try {                        pic.writeImageContent(new FileOutputStream("E:/test/"+pic.suggestFullFileName()));                    } catch (FileNotFoundException e) {                        e.printStackTrace();                    }                }            }            wordToHtmlConverter.processDocument(wordDocument);            Document htmlDocument = wordToHtmlConverter.getDocument();            ByteArrayOutputStream outStream = new ByteArrayOutputStream();            DOMSource domSource = new DOMSource(htmlDocument);            StreamResult streamResult = new StreamResult(outStream);            TransformerFactory tf = TransformerFactory.newInstance();            Transformer serializer = tf.newTransformer();            serializer.setOutputProperty(OutputKeys.ENCODING, "utf-8");            serializer.setOutputProperty(OutputKeys.INDENT, "yes");            serializer.setOutputProperty(OutputKeys.METHOD, "html");            serializer.transform(domSource, streamResult);            outStream.close();            String content = new String(outStream.toByteArray());            response.getOutputStream().write(outStream.toByteArray());   //3、PDF+TXT JPG JPEG  BufferedReader bis = null;  BufferedInputStream br = new BufferedInputStream(gridFSDBFile.getInputStream());  response.setHeader("Content-Disposition",            "inline; filename=" + URLEncoder.encode(gridFSDBFile.getFilename(), "UTF-8"));  OutputStream out = response.getOutputStream();  byte[] buf = new byte[1024];  int len = 0;  while ((len = br.read(buf)) != -1)  out.write(buf, 0, len);  br.close();  out.close();                  } catch (Exception e) {                e.printStackTrace();            }        }