利用POI技术实现导出excel报表

这个是很固定的代码步骤，下面会有三段代码，前面两段是基础介绍，最后一段基本可以复制下来，所有场景基本上都能套用。
maven工程中所需要的poi依赖：

   <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi</artifactId>
      <version>4.0.1</version>
    </dependency>
    
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>4.0.1</version>
    </dependency>
    
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml-schemas</artifactId>
      <version>4.0.1</version>
    </dependency>

一、向excel表格中写数据

 @Test
    public void TestPoi() throws Exception {
        //获取对应的excel文件,工作簿文件
        XSSFWorkbook sheets = new XSSFWorkbook();
        //创建工作表
        XSSFSheet sheet = sheets.createSheet();
        sheets.createSheet("nishi");
        //创建工作表中的行对象，方法中的数字代表行的索引，第一行的索引是0
        XSSFRow row = sheet.createRow(1);
        //创建工作表中的列对象，方法中的数字代表行的索引，第一列的索引是0
        XSSFCell cell = row.createCell(1);
        //在列中写数据
        cell.setCellValue("你好");
        //创建一个文件对象，作为excel文件内容的输出文件
        File file = new File("test.xlsx");
        //输出时通过流的形式对外输出，包装对应的目标文件
        FileOutputStream fileOutputStream = new FileOutputStream(file);
        //将内存中的workboook数据写入流中
        sheets.write(fileOutputStream);
        sheets.close();
        fileOutputStream.close();
    }

二、在excel表格中读取数据

 @Test
    public void TestReadPoi() throws Exception {
        //获取要读取文件的工作簿对象
        XSSFWorkbook wb = new XSSFWorkbook("test.xlsx");
        /*//获取工作表，根据表格的名称拿数据
        XSSFSheet sheet = wb.getSheet("sheet0");*/
        //获取工作表，根据表格的索引拿数据
        XSSFSheet sheet = wb.getSheetAt(0);
        //获取行
        XSSFRow row = sheet.getRow(1);
        //获取列
        XSSFCell cell = row.getCell(1);
        //根据数据类型获取数据
        String data = cell.getStringCellValue();
        System.out.println(data);
        //释放资源
        wb.close();
    }

三、循环往excel中写入数据

 @Test
    public void testProjectPoi() throws IOException {
        //1.获取到对应的Excel文件，工作簿文件
        Workbook wb = new XSSFWorkbook();
        //2.创建工作表
        Sheet s = wb.createSheet("题目数据文件");

        //设置通用配置
//        s.setColumnWidth(4,100);
        CellStyle cs_field = wb.createCellStyle();
        cs_field.setAlignment(HorizontalAlignment.CENTER);
        cs_field.setBorderTop(BorderStyle.THIN);
        cs_field.setBorderBottom(BorderStyle.THIN);
        cs_field.setBorderLeft(BorderStyle.THIN);
        cs_field.setBorderRight(BorderStyle.THIN);

        //制作标题
        s.addMergedRegion(new CellRangeAddress(1,1,1,12));

        Row row_1 = s.createRow(1);
        Cell cell_1_1 = row_1.createCell(1);
        cell_1_1.setCellValue("在线试题导出信息");
        //创建一个样式
        CellStyle cs_title = wb.createCellStyle();
        cs_title.setAlignment(HorizontalAlignment.CENTER);
        cs_title.setVerticalAlignment(VerticalAlignment.CENTER);
        cell_1_1.setCellStyle(cs_title);

        //制作表头
        String[] fields = {"题目ID","所属公司ID","所属目录ID","题目简介","题干描述",
                "题干配图","题目分析","题目类型","题目难度","是否经典题","题目状态","审核状态"};
        //创建第二行的行对象
        Row row_2 = s.createRow(2);
        //遍历写表头
        for (int i = 0; i < fields.length; i++) {
            Cell cell_2_temp = row_2.createCell(1 + i); //++
            cell_2_temp.setCellValue(fields[i]);    //++
            cell_2_temp.setCellStyle(cs_field);
        }

        //制作数据区,下面是为了测试随便写的数据，一般是通过数据库来拿数据进行展示，然后写出到excel中
        List<Question> questionList = new ArrayList<>();
        Question qq = new Question();
        qq.setId("1");
        qq.setPicture("12");
        qq.setReviewStatus("13");
        qq.setAnalysis("14");
        qq.setCatalogId("15");
        qq.setCompanyId("16");
        qq.setDifficulty("17");
        qq.setIsClassic("18");
        qq.setRemark("19");
        qq.setState("21");
        qq.setSubject("31");
        qq.setType("41");
        questionList.add(qq);
        //定义行自增的初始值
        int row_index = 0;
        //遍历写数据
        for (Question q : questionList) {
            //定义列的初始自增值
            int cell_index = 0;
            //创建第三行的行对象，每写完一次，行数加1，写下一行
            Row row_temp = s.createRow(3 + row_index++);

            Cell cell_data_1 = row_temp.createCell(1 + cell_index++);
            cell_data_1.setCellValue(q.getId());    //++
            cell_data_1.setCellStyle(cs_field);

            Cell cell_data_2 = row_temp.createCell(1 + cell_index++);
            cell_data_2.setCellValue(q.getCompanyId());    //++
            cell_data_2.setCellStyle(cs_field);

            Cell cell_data_3 = row_temp.createCell(1 + cell_index++);
            cell_data_3.setCellValue(q.getCatalogId());    //++
            cell_data_3.setCellStyle(cs_field);

            Cell cell_data_4 = row_temp.createCell(1 + cell_index++);
            cell_data_4.setCellValue(q.getRemark());    //++
            cell_data_4.setCellStyle(cs_field);

            Cell cell_data_5 = row_temp.createCell(1 + cell_index++);
            cell_data_5.setCellValue(q.getSubject());    //++
            cell_data_5.setCellStyle(cs_field);

            Cell cell_data_6 = row_temp.createCell(1 + cell_index++);
            cell_data_6.setCellValue(q.getPicture());    //++
            cell_data_6.setCellStyle(cs_field);

            Cell cell_data_7 = row_temp.createCell(1 + cell_index++);
            cell_data_7.setCellValue(q.getAnalysis());    //++
            cell_data_7.setCellStyle(cs_field);

            Cell cell_data_8 = row_temp.createCell(1 + cell_index++);
            cell_data_8.setCellValue(q.getType());    //++
            cell_data_8.setCellStyle(cs_field);

            Cell cell_data_9 = row_temp.createCell(1 + cell_index++);
            cell_data_9.setCellValue(q.getDifficulty());    //++
            cell_data_9.setCellStyle(cs_field);

            Cell cell_data_10 = row_temp.createCell(1 + cell_index++);
            cell_data_10.setCellValue(q.getIsClassic());    //++
            cell_data_10.setCellStyle(cs_field);

            Cell cell_data_11 = row_temp.createCell(1 + cell_index++);
            cell_data_11.setCellValue(q.getState());    //++
            cell_data_11.setCellStyle(cs_field);

            Cell cell_data_12 = row_temp.createCell(1 + cell_index++);
            cell_data_12.setCellValue(q.getReviewStatus());    //++
            cell_data_12.setCellStyle(cs_field);
        }

        //创建一个文件对象，作为excel文件内容的输出文件
        File f = new File("test.xlsx");
        //输出时通过流的形式对外输出，包装对应的目标文件
        OutputStream os = new FileOutputStream(f);
        //将内存中的workbook数据写入到流中
        wb.write(os);
        wb.close();
        os.close();
    }