FastExcel 2025 最新教程：解决大文件内存溢出与百万级数据读写

try (FastExcelReader reader = new FastExcelReader(new FileInputStream("large_data.xlsx"))) {
    Sheet sheet = reader.getSheet();
    for (Row row : sheet) {
        // 处理每一行数据
        System.out.println(row.getCells());
    }
}

try (FastExcelWriter writer = new FastExcelWriter(new FileOutputStream("users.xlsx"))) {
    Sheet sheet = writer.newSheet("Users");
    sheet.writeRow(Arrays.asList("ID", "Name", "Email"));
    for (int i = ; i <= ; i++) {
        sheet.writeRow(Arrays.asList(String.valueOf(i), "User" + i, "user" + i + "@example.com"));
    }
    System.out.println("Export complete.");
}

@PostMapping("/upload")
public ResponseEntity<String> uploadExcel(@RequestParam("file") MultipartFile file) {
    if (file.isEmpty()) {
        return ResponseEntity.badRequest().body("请选择一个文件上传！");
    }
    try {
        Long start = System.currentTimeMillis();
        BaseExcelListener<User> baseExcelListener = new BaseExcelListener<>();
        FastExcel.read(file.getInputStream(), User.class, baseExcelListener).sheet().doRead();
        List<User> dataList = baseExcelListener.getDataList();
        System.out.println(dataList.size());
        Long end = System.currentTimeMillis();
        return ResponseEntity.ok("文件上传并处理成功！耗时：" + (end - start) + "ms");
    } catch (IOException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("文件处理失败！");
    }
}