上一篇檔案上傳【點選跳轉】，是將路徑等檔案資訊存進log_file臨時表，內容二進位制存入資料庫Test表，這種邏輯是在呼叫資料庫表Test內容展示時，判斷檔案為word(轉換成pdf)還是pdf(直接展示)。 上一篇連結：連結地址。 下面進一步優化： 具體邏輯：刪除原資料表Test，路徑等檔案資訊依舊存log_file表。檔案預覽時，判斷檔案型別，如果為word型別，進行轉換pdf展示；反之直接展示檔案。 word型別條件滿足後，進一步判斷檔案是否已經轉換過(判斷依據是根據路徑下檔名查詢相同檔名的pdf檔案是否存在)，如果同名的pdf檔案存在，表示已經轉換過，直接展示；如果不存在，word轉換pdf，再展示。

程式碼如下：

public void world(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws IOException {
        List<LogFile> files = terminalServiceImpl.world();
        //用作例項展示，在這取得是資料庫第二條資訊：以word檔案展示。
        String path = files.get(1).getFilePath();
        String filename=files.get(1).getFileName();

        //1.根據檔案字尾獲取檔案型別
        File wordName=new File(filename);
        String fileName=wordName.getName();
        String fileTyle=fileName.substring(fileName.lastIndexOf("."),fileName.length());
        logger.info("------檔案字尾名------"+fileTyle);

        //如果檔案型別為word,需要先轉換成pdf
        if(fileTyle.equals(".doc")||fileTyle.equals(".docx")){
                //1.判斷檔案是否已經轉換pdf,檔案是否存在：檔案字首+.pdf(word是否已經轉換過pdf)，如果存在直接展示pdf
                File fileOne = new File(path);
                String caselsh = filename.substring(0,filename.lastIndexOf("."));
                logger.info("------pdf檔名字------"+caselsh+"pdf.pdf");
//                File fileIf = new File(fileOne+"\\" + caselsh+".pdf");
                String filePath=(fileOne+"\\" + caselsh+"pdf.pdf");
                File fileIf=new File(filePath);
                if(!fileIf.exists()){
                    String pdfFilePath = OpenOfficeUtil.wordToPDF(path,filename);
                    System.err.println(pdfFilePath);
                    FileInputStream fileInputStream = new FileInputStream(pdfFilePath);
                    byte[] content = new byte[fileInputStream.available()];
                    fileInputStream.read(content);
                    fileInputStream.close();
                    ServletOutputStream servletOutputStream = httpServletResponse.getOutputStream();
                    if (servletOutputStream != null && content != null){
                        httpServletResponse.setContentType("application/pdf");
                        httpServletResponse.setContentLength(content.length);
                        httpServletResponse.setHeader("Expires","0");
                        httpServletResponse.setHeader("Cache-Control","must-revalidate,post-check=0,pre-check=0");
                        httpServletResponse.setHeader("Pragma","public");
                        servletOutputStream.write(content);
                        servletOutputStream.flush();
                        servletOutputStream.close();
                    }
                }else{
                    File file3 = new File(filePath);
                    //獲取pdf檔案路徑,內容做展示
                    byte[] resultE = new byte[(int) file3.length()];
                    FileInputStream fis = new FileInputStream(file3);
                    fis.read(resultE); //read file into bytes[]
                    fis.close();
                    ServletOutputStream servletOutputStream = httpServletResponse.getOutputStream();
                    if (servletOutputStream != null && resultE != null){
                        httpServletResponse.setContentType("application/pdf");
                        httpServletResponse.setContentLength(resultE.length);
                        httpServletResponse.setHeader("Expires","0");
                        httpServletResponse.setHeader("Cache-Control","must-revalidate,post-check=0,pre-check=0");
                        httpServletResponse.setHeader("Pragma","public");
                        servletOutputStream.write(resultE);
                        servletOutputStream.flush();
                        servletOutputStream.close();
                    }
            }
        }else{
            File file = new File(path);
            File file2 = new File(file+"\\" + filename);
            //獲取pdf檔案路徑,內容做展示
            byte[] result = new byte[(int) file2.length()];
            FileInputStream fis = new FileInputStream(file2);
            fis.read(result); //read file into bytes[]
            fis.close();
            ServletOutputStream servletOutputStream = httpServletResponse.getOutputStream();
            if (servletOutputStream != null && result != null){
                httpServletResponse.setContentType("application/pdf");
                httpServletResponse.setContentLength(result.length);
                httpServletResponse.setHeader("Expires","0");
                httpServletResponse.setHeader("Cache-Control","must-revalidate,post-check=0,pre-check=0");
                httpServletResponse.setHeader("Pragma","public");
                servletOutputStream.write(result);
                servletOutputStream.flush();
                servletOutputStream.close();
            }
        }
   }