poi 操作Excel 以及大数据量导出

maven 依赖 （版本必须一致，否则使用SXSSFworkbook 时程序会报错）

<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>

HSSFworkbook,XSSFworkbook,SXSSFworkbook 三者 区别

HSSFworkbook：操作Excel2003版本，扩展名为xls

XSSFworkbook：操作Excel2007版本，扩展名为xlsx

SXSSFworkbook ：用于大数据量导出，当数据量超过 65536后 程序 会报错：Invalid row number (65536) outside allowable range (0..65535)

例子1：简单导出Excel

 @Test
    public void test1() throws IOException {
        // 读取文件
        POIFSFileSystem fs = new POIFSFileSystem(Thread.currentThread().getContextClassLoader().getResourceAsStream("test.xls"));
        // 创建一个工作簿
        HSSFWorkbook workbook = new HSSFWorkbook(fs);
        // 获取第一个sheet
        HSSFSheet sheet = workbook.getSheetAt(0);
        System.out.println(sheet.getSheetName());
        // 获取第一行
        HSSFRow row = sheet.getRow(0);
        // 获取第一行第一列
        HSSFCell cell = row.getCell(0);
        System.out.println(cell.getStringCellValue());

        // 创建一行
        HSSFRow row1 = sheet.createRow(1);
        // 创建单元格
        HSSFCell cell1 = row1.createCell(0);
        // 单元格赋值
        cell1.setCellValue("我是程序创建的内容");
        System.out.println(cell1.getStringCellValue());

        // 创建输出流
        FileOutputStream os = new FileOutputStream(new File("D:\\8888.xls"));
        // 输出文件
        workbook.write(os);
    }

例子2：导出查询数据

 @Test
    public void test2() {
        // 模拟导出数据
        Object[] obj = new Object[]{"哈哈", "呵呵", "哼哼"};
        List<Object[]> list = new ArrayList<Object[]>();
        // HSSFWorkbook 只支持2003版本及以下版本Excel 且容量最大为65536
        for (int i = 0; i < 65536; i++) {
            list.add(obj);
        }

        export("test.xls", list, 2);
    }

    /**
     * poi 导出
     * @param fileName
     * @param objs
     * @param rowIndex
     */
    private void export(String fileName, List<Object[]> objs, int rowIndex) {
        POIFSFileSystem fs = null;
        FileOutputStream os = null;
        try {
            fs = new POIFSFileSystem(Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName));
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 创建一个工作簿
        try {
            HSSFWorkbook workbook = new HSSFWorkbook(fs);
            HSSFCellStyle style = setCellStyle(workbook);
            // 获取一个sheet页
            HSSFSheet sheet = workbook.getSheetAt(0);

            for (int i = rowIndex - 1; i < objs.size(); i++) {
                // 创建行
                HSSFRow row = sheet.createRow(i);

                // 创建列
                for (int j = 0; j < objs.get(i).length; j++) {
                    HSSFCell cell = row.createCell(j);
                    // 设置单元格样式
                    cell.setCellStyle(style);
                    cell.setCellValue(objs.get(i)[j].toString());
                }
            }
            // 创建输出流
             os = new FileOutputStream(new File("D:\\8888.xls"));
            // 输出文件
            workbook.write(os);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    /**
     * 设置样式
     * @param workbook
     */
    private HSSFCellStyle setCellStyle(HSSFWorkbook workbook) {
        HSSFCellStyle style = workbook.createCellStyle();
        HSSFFont font = workbook.createFont();
        // 字号
        font.setFontHeightInPoints((short) 12);
        style.setFont(font);
        // 左右居中 上下居中
        style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        style.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
        return style;
    }

例子3：大数据量导出

/**
     * 大数据量导出
     * @throws IOException
     */
    @Test
    public void text2() throws IOException {

        XSSFWorkbook xssfWorkbook = new   XSSFWorkbook(Thread.currentThread().getContextClassLoader().getResourceAsStream("bigdata.xlsx"));
        SXSSFWorkbook wb = new SXSSFWorkbook(xssfWorkbook, 100);

        Sheet sh = wb.getSheetAt(0);
        for(int rownum = 1; rownum < 75537; rownum++){
            Row row = sh.createRow(rownum);
            for(int cellnum = 0; cellnum < 10; cellnum++){
                Cell cell = row.createCell(cellnum);
                String address = new CellReference(cell).formatAsString();
                cell.setCellValue(address);
            }

        }

//        // Rows with rownum < 900 are flushed and not accessible
//        for(int rownum = 0; rownum < 900; rownum++){
//            Assert.assertNull(sh.getRow(rownum));
//        }
//
//        // ther last 100 rows are still in memory
//        for(int rownum = 900; rownum < 1000; rownum++){
//            Assert.assertNotNull(sh.getRow(rownum));
//        }

        FileOutputStream out = new FileOutputStream("D:\\sxssf.xlsx");
        wb.write(out);
        out.close();

        // dispose of temporary files backing this workbook on disk
        wb.dispose();
    }