java实现赋值excel模板，并在新文件中写入数据，并且下载

    /**
     * 生成excel并下载
     */
    public void exportExcel(){

        File newFile = createNewFile();
        //File newFile = new File("d:/ss.xls");

        //新文件写入数据，并下载*****************************************************
        InputStream is = null;
        HSSFWorkbook workbook = null;
        HSSFSheet sheet = null;
        try {
            is = new FileInputStream(newFile);
            workbook = new HSSFWorkbook(is);
            //获取第一个sheet
            sheet = workbook.getSheetAt(0);
        } catch (Exception e1) {
            e1.printStackTrace();
        }

        if(sheet != null){
            try {
                //写数据
                FileOutputStream fos = new FileOutputStream(newFile);
                HSSFRow row = sheet.getRow(4);
                HSSFCell cell = row.getCell(1);
                System.out.println(cell.getStringCellValue());
                cell.setCellValue("ssssssssssssssssssssssssssssssssssssssssssss");
                workbook.write(fos);
                fos.flush();
                fos.close();

                //下载
               InputStream fis = new BufferedInputStream(new FileInputStream(newFile));
               HttpServletResponse response = this.getResponse();
               byte[] buffer = new byte[fis.available()];
               fis.read(buffer);
               fis.close();
               response.reset();
               response.setContentType("text/html;charset=UTF-8");
               OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
                  response.setContentType("application/x-msdownload");
                  String newName = URLEncoder.encode("采购合同"+System.currentTimeMillis()+".xls", "UTF-8");
                  response.addHeader("Content-Disposition", "attachment;filename=\""+ newName + "\"");
                  response.addHeader("Content-Length", "" + newFile.length());
               toClient.write(buffer);
               toClient.flush();
            }
            catch(Exception e) {
                e.printStackTrace();
            }finally {
                try {
                    if (null != is) {
                        is.close();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
        //删除创建的新文件
        //this.deleteFile(newFile);
    }
    /**
    * 复制文件
    *
    * @param s
    * 源文件
    * @param t
    * 复制到的新文件
    */

    public void fileChannelCopy(File s, File t) {
        try {
            InputStream in = null;
            OutputStream out = null;
            try {
                in = new BufferedInputStream(new FileInputStream(s),1024);
                out = new BufferedOutputStream(new FileOutputStream(t),1024);
                byte[] buffer = new byte[1024];
                int len;
                while ((len=in.read(buffer))!=-1) {
                    out.write(buffer,0,len);
                }
            } finally {
                if (null != in) {
                    in.close();
                }
                if (null != out) {
                    out.close();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 读取excel模板，并复制到新文件中供写入和下载
     * @return
     */
    public File createNewFile(){
        //读取模板，并赋值到新文件************************************************************
        //文件模板路径
        String path = this.getRequest().getRealPath(SystemConfig.FILETEMPLATE);
        String fileName="purchaseContract.xls";
        File file=new File(path+"/"+fileName);

        //保存文件的路径
        String realPath = ServletActionContext.getServletContext().getRealPath(SystemConfig.UPLOAD_FILE_DIR);
        //新的文件名
        String newFileName = "采购合同"+System.currentTimeMillis() + ".xls";
        //判断路径是否存在
        File dir = new File(realPath);
        if(!dir.exists()){
            dir.mkdirs();
        }
        //写入到新的excel
        File newFile = new File(realPath, newFileName);
        try {
            newFile.createNewFile();
            //复制模板到新文件
            fileChannelCopy(file, newFile);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return newFile;
    }

    /**
     * 下载成功后删除
     *
     * @param files
     */
    private void deleteFile(File... files) {
        for (File file : files) {
            if (file.exists()) {
                file.delete();
            }
        }
    }