Java如何用POI导入导出Excel

  <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.9</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.9</version>
        </dependency>

//上传Excel
    @RequestMapping("/uploadExcel")    public boolean uploadExcel(@RequestParam MultipartFile file,HttpServletRequest request) throws IOException {        if(!file.isEmpty()){
            String filePath = file.getOriginalFilename();            //windows
            String savePath = request.getSession().getServletContext().getRealPath(filePath);            //linux            //String savePath = "/home/odcuser/webapps/file";
            File targetFile = new File(savePath);            if(!targetFile.exists()){
                targetFile.mkdirs();
            }

            file.transferTo(targetFile);            return true;
        }        return false;
    }

 public static void readExcel() throws Exception{


        InputStream is = new FileInputStream(new File(fileName));
        Workbook hssfWorkbook = null;        if (fileName.endsWith("xlsx")){
           hssfWorkbook = new XSSFWorkbook(is);//Excel 2007
        }else if (fileName.endsWith("xls")){
            hssfWorkbook = new HSSFWorkbook(is);//Excel 2003
        }       // HSSFWorkbook hssfWorkbook = new HSSFWorkbook(is);       // XSSFWorkbook hssfWorkbook = new XSSFWorkbook(is);
        User student = null;
        List<User> list = new ArrayList<User>();        // 循环工作表Sheet
        for (int numSheet = 0; numSheet <hssfWorkbook.getNumberOfSheets(); numSheet++) {            //HSSFSheet hssfSheet = hssfWorkbook.getSheetAt(numSheet);
            Sheet hssfSheet = hssfWorkbook.getSheetAt(numSheet);            if (hssfSheet == null) {                continue;
            }            // 循环行Row
            for (int rowNum = 1; rowNum <= hssfSheet.getLastRowNum(); rowNum++) {                //HSSFRow hssfRow = hssfSheet.getRow(rowNum);
                Row hssfRow = hssfSheet.getRow(rowNum);                if (hssfRow != null) {
                    student = new User();                    //HSSFCell name = hssfRow.getCell(0);                    //HSSFCell pwd = hssfRow.getCell(1);
                    Cell name = hssfRow.getCell(0);
                    Cell pwd = hssfRow.getCell(1);//这里是自己的逻辑                    student.setUserName(name.toString());
                    student.setPassword(pwd.toString());

                    list.add(student);
                }
            }
        }


    }

//创建Excel
    @RequestMapping("/createExcel")    public String createExcel(HttpServletResponse response) throws IOException {        //创建HSSFWorkbook对象(excel的文档对象)
        HSSFWorkbook wb = new HSSFWorkbook();//建立新的sheet对象（excel的表单）
        HSSFSheet sheet=wb.createSheet("成绩表");//在sheet里创建第一行，参数为行索引(excel的行)，可以是0～65535之间的任何一个
        HSSFRow row1=sheet.createRow(0);//创建单元格（excel的单元格，参数为列索引，可以是0～255之间的任何一个
        HSSFCell cell=row1.createCell(0);        //设置单元格内容
        cell.setCellValue("学员考试成绩一览表");//合并单元格CellRangeAddress构造参数依次表示起始行，截至行，起始列， 截至列
        sheet.addMergedRegion(new CellRangeAddress(0,0,0,3));//在sheet里创建第二行
        HSSFRow row2=sheet.createRow(1);        //创建单元格并设置单元格内容
        row2.createCell(0).setCellValue("姓名");
        row2.createCell(1).setCellValue("班级");
        row2.createCell(2).setCellValue("笔试成绩");
        row2.createCell(3).setCellValue("机试成绩");        //在sheet里创建第三行
        HSSFRow row3=sheet.createRow(2);
        row3.createCell(0).setCellValue("李明");
        row3.createCell(1).setCellValue("As178");
        row3.createCell(2).setCellValue(87);
        row3.createCell(3).setCellValue(78);        //.....省略部分代码//输出Excel文件
        OutputStream output=response.getOutputStream();
        response.reset();
        response.setHeader("Content-disposition", "attachment; filename=details.xls");
        response.setContentType("application/msexcel");
        wb.write(output);
        output.close();        return null;
    }

public static String toUtf8String(String s){ 
     StringBuffer sb = new StringBuffer(); 
       for (int i=0;i<s.length();i++){ 
          char c = s.charAt(i); 
          if (c >= 0 && c <= 255){sb.append(c);} 
        else{ 
        byte[] b; 
         try { b = Character.toString(c).getBytes("utf-8");} 
         catch (Exception ex) { 
             System.out.println(ex); 
                  b = new byte[0]; 
         } 
            for (int j = 0; j < b.length; j++) { 
             int k = b[j]; 
              if (k < 0) k += 256; 
              sb.append("%" + Integer.toHexString(k).toUpperCase()); 
              } 
     } 
  } 
  return sb.toString(); 
}