EasyPoi介绍:

利用注解的方式简化了Excel、Word、PDF等格式的导入导出，而且是百万级数据的导入导出。EasyPoi官方网址：EasyPoi教程_V1.0 (mydoc.io)。下面我写了一个测试用例，真的是很方便，可以利用注解自动完成单元格的合并，设置单元格宽度、设置字符替换、并且可以很好的完成实体类之间一对一、一对多关系的处理

不卖关子，事先说明百万级大数据操作使用：导入（importExcelBySax），导出（exportBigExcel）

• 导入依赖

<dependency>
    <groupId>cn.afterturn</groupId>
    <artifactId>easypoi-base</artifactId>
    <version>4.1.0</version>
</dependency>
<dependency>
    <groupId>cn.afterturn</groupId>
    <artifactId>easypoi-web</artifactId>
    <version>4.1.0</version>
</dependency>
<dependency>
    <groupId>cn.afterturn</groupId>
    <artifactId>easypoi-annotation</artifactId>
    <version>4.1.0</version>
</dependency>

• 实体对象

/**
 * 免打扰手机号
 *
 * @author Mark sunlightcs@gmail.com
 * @since 1.0.0
 */
@Data
public class NonIntrusiveExcel {
    @Excel(name = "手机号码", width = 20)
    @NotNull
    private String phone;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        NonIntrusiveExcel that = (NonIntrusiveExcel) o;
        return phone.equals(that.phone);
    }

    @Override
    public int hashCode() {
        return Objects.hash(phone);
    }
}

• 导入导出工具类

/**
 * excel工具类
 *
 * excel中xls和xlsx的区别是：
 * 1、文件格式不同。xls是一个特有的二进制格式，其核心结构是复合文档类型的结构，而xlsx的核心结构是XML类型的结构，采用的是基于 XML 的压缩方式，使其占用的空间更小。xlsx 中最后一个 x 的意义就在于此。
 * 2、版本不同。xls是excel2003及以前版本生成的文件格式，而xlsx是excel2007及以后版本生成的文件格式。
 * 3、兼容性不同。xlsx格式是向下兼容的，可兼容xls格式。
 *
 * @author Mark sunlightcs@gmail.com
 */
public class ExcelUtils {

    /**
     * Excel导入
     *
     * @param request       request
     * @param pojoClass     对象Class
     */
    public static List importExcel(HttpServletRequest request, Class<?> pojoClass) throws IOException {
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        MultipartFile file = multipartRequest.getFile("file");
        if (file == null) {
            throw new RenException("未找到上传的文件！");
        }
        ImportParams params = new ImportParams();
        params.setHeadRows(1);
        params.setNeedVerify(true); // 开启校验规则
        List targetList = null;

        try {
            System.out.println("正在读取文件: " + file.getOriginalFilename() + "，开始导入数据。");
            targetList = ExcelImportUtil.importExcel(file.getInputStream(), pojoClass, params);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            file.getInputStream().close();
        }

        return targetList;
    }

    /**
     * Excel大数据导入
     *
     * @param request       request
     * @param pojoClass     对象Class
     */
    public static Set importBigExcel(HttpServletRequest request, Class<?> pojoClass) throws IOException {
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        MultipartFile file = multipartRequest.getFile("file");
        if (file == null) {
            throw new RenException("未找到上传的文件！");
        }
        ImportParams params = new ImportParams();
        params.setHeadRows(1);
        params.setNeedVerify(true); // 开启校验规则
        Set targetList = new HashSet(); // 添加set集合过滤去重元素

        try {
            System.out.println("正在读取文件: " + file.getOriginalFilename() + "，开始导入数据。");
            ExcelImportUtil.importExcelBySax(file.getInputStream(), pojoClass, params, new IReadHandler() {
                @Override
                public void handler(Object o) {
                    targetList.add(o);
                }

                @Override
                public void doAfterAll() {

                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            file.getInputStream().close();
        }

        return targetList;
    }

    /**
     * Excel导出
     *
     * @param response      response
     * @param fileName      文件名
     * @param list          数据List
     * @param pojoClass     对象Class
     */
    public static void exportExcel(HttpServletResponse response, String fileName, Collection<?> list,
                                   Class<?> pojoClass) throws IOException {
        if (StringUtils.isBlank(fileName)) {
            //当前日期
            fileName = DateUtil.formatDatetime(new Date());
        }

        // 设置导出格式为xlsx，默认xlsx
        ExportParams exportParams = new ExportParams();
        exportParams.setType(ExcelType.XSSF);

        Workbook workbook = ExcelExportUtil.exportExcel(exportParams, pojoClass, list);
        response.setCharacterEncoding("UTF-8");
        response.setHeader("content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,application/vnd.ms-excel");
//        response.setHeader("content-Type", "application/vnd.ms-excel");
        response.setHeader("Content-Disposition",
                "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8") + ".xlsx");
        ServletOutputStream out = response.getOutputStream();
        workbook.write(out);
        out.flush();
    }

    /**
     * Excel大数据导出
     *
     * @param list          数据List
     * @param pojoClass     对象Class
     */
    public static byte[] exportBigExcelByte(Collection<?> list, Class<?> pojoClass) throws IOException {
        Workbook workbook;

        // 设置导出单sheet页最大一百万行数据
        ExportParams exportParams = new ExportParams();
        exportParams.setMaxNum(1000000);
        exportParams.setType(ExcelType.XSSF);

        workbook = ExcelExportUtil.exportBigExcel(exportParams, pojoClass, (queryParams, num) -> {
            // 只导出一次，第二次返回null终止循环
            if (((int) queryParams) == num) {
                return null;
            }
            System.out.println("正在进行大数据量导出，条数: " + list.size());
            return Arrays.asList(list.toArray());
        }, 2);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        workbook.write(bos);
        bos.close();

        byte[] bytes = bos.toByteArray();

        return bytes;
    }

    /**
     * Excel导出，先sourceList转换成List<targetClass>，再导出
     *
     * @param response      response
     * @param fileName      文件名
     * @param sourceList    原数据List
     * @param targetClass   目标对象Class
     */
    public static void exportExcelToTarget(HttpServletResponse response, String fileName, Collection<?> sourceList,
                                           Class<?> targetClass) throws Exception {
        List targetList = new ArrayList<>(sourceList.size());
        for (Object source : sourceList) {
            Object target = targetClass.newInstance();
            BeanUtils.copyProperties(source, target);
            targetList.add(target);
        }

        exportExcel(response, fileName, targetList, targetClass);
    }

    /**
     * Excel生成
     *
     * @param response      response
     * @param fileName      文件名
     */
    public static void mkdirExcel(HttpServletResponse response, String fileName,
                                  Workbook workbook) throws IOException {
        if (StringUtils.isBlank(fileName)) {
            //当前日期
            fileName = DateUtil.formatDatetime(new Date());
        }

        response.setCharacterEncoding("UTF-8");
        response.setHeader("content-Type", "application/vnd.ms-excel");
        response.setHeader("Content-Disposition",
                "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8") + ".xls");
        ServletOutputStream out = response.getOutputStream();
        workbook.write(out);
        out.flush();
    }

    /**
     * XSSF
     * excel添加下拉数据校验
     *
     * @param workbook   哪个 sheet 页添加校验
     * @param dataSource 数据源数组
     * @param col        第几列校验（0开始）
     * @return
     */
    public static void createXssfSelected(Workbook workbook, String[] dataSource, int col) {
        Sheet sheet = workbook.getSheetAt(0);
        CellRangeAddressList cellRangeAddressList = new CellRangeAddressList(1, 65535, col, col);
        DataValidationHelper helper = sheet.getDataValidationHelper();
        DataValidationConstraint constraint = helper.createExplicitListConstraint(dataSource);
        DataValidation dataValidation = helper.createValidation(constraint, cellRangeAddressList);
        //处理Excel兼容性问题
        if (dataValidation instanceof XSSFDataValidation) {
            dataValidation.setSuppressDropDownArrow(true);
            dataValidation.setShowErrorBox(true);
        } else {
            dataValidation.setSuppressDropDownArrow(false);
        }
        dataValidation.setEmptyCellAllowed(true);
        dataValidation.setShowPromptBox(true);
        dataValidation.createPromptBox("提示", "只能选择下拉框里面的数据");
        sheet.addValidationData(dataValidation);
    }

}

• 接口调用

@RestController
@RequestMapping("/app/nonIntrusive")
@Slf4j
public class NonIntrusiveController {
    @Autowired
    private NonIntrusiveService appNonIntrusiveService;

    @PostMapping(value = "/importAndExportFilter")
    @LogOperation("免打扰过滤")
    @RequiresPermissions("app:nonIntrusive:filter")
    public byte[] importFilter(HttpServletRequest request) throws Exception {
        long startTime = System.currentTimeMillis();

        // 读取excel文件内容转成集合
        Set<NonIntrusiveExcel> importSet = ExcelUtils.importBigExcel(request, NonIntrusiveExcel.class);

        log.info("已读取文件内容条数：{}, 总共耗时：{} 毫秒", importSet.size(), System.currentTimeMillis() - startTime);

        startTime = System.currentTimeMillis();

        // 读取数据表列表集合
        Set<NonIntrusiveExcel> phoneSet = appNonIntrusiveService.listExcel();

        log.info("已加载存储的免打扰号码库总条数：{}, 总共耗时：{} 毫秒", phoneSet.size(), System.currentTimeMillis() - startTime);

        startTime = System.currentTimeMillis();

        // Set排除已存在的集合数据
        importSet.removeAll(phoneSet);

        log.info("已完成过滤免打扰号码后的总条数：{}, 总共耗时：{} 毫秒", importSet.size(), System.currentTimeMillis() - startTime);

        // 进行大数据excel导出
        return ExcelUtils.exportBigExcelByte(importSet, NonIntrusiveExcel.class);
    }

    @GetMapping(value = "/exportTemplate")
    public void export(HttpServletResponse response) throws Exception {
        ExcelUtils.exportExcelToTarget(response, null, new ArrayList<>(), NonIntrusiveExcel.class);
    }

}