easypoi 导出报错 UnsupportedOperationException: null

1. 调用 ExcelExportUtil.exportExcel 导出失败

        // 1. 构建导出参数
        ExportParams exportParams = new ExportParams(title, sheetName, ExcelType.XSSF);

        // 2. 属性拷贝：T -> R
        List<R> targetList = failList.stream()
                .map(source -> BeanUtil.copyProperties(source, targetClz))
                .toList();

        // 3. 导出并转 Base64
        try (Workbook workbook = ExcelExportUtil.exportExcel(exportParams, targetClz, targetList);
             ByteArrayOutputStream out = new ByteArrayOutputStream()) {

            workbook.write(out);
            return Base64.getEncoder().encodeToString(out.toByteArray());

        } catch (Exception e) {
            log.error("导出失败数据 Excel 时发生异常", e);
            throw new BusinessException("导出失败数据 Excel 时发生异常");
        }

2.报错

3.原因

    List<R> targetList = failList.stream()
        .map(source -> BeanUtil.copyProperties(source, targetClz))
        .toList();

使用了 toList() 得到不可变List
4.解决

List<R> targetList = failList.stream()
    .map(e -> BeanUtil.copyProperties(e, targetClz))
    .collect(Collectors.toList());

改为 Collectors.toList() 返回的是可变 ArrayList