poi 解析excel 以及Function＜T,R＞的使用

Function<T,R> T是参数，R是返回值，可以作为参数传递到方法中

/**
 * excel 解析工具
 */
@Slf4j
public class ExcelUtils {

    private List getWorkBook(String filePath, Function<Workbook, List> function) throws IOException {
        Workbook workbook;
        String ext = filePath.substring(filePath.lastIndexOf(".") + 1).toLowerCase();
        try (InputStream inputStream = new FileInputStream(filePath)) {
            if (ext.equals("xls")) {
                workbook = new HSSFWorkbook(inputStream);
            } else {
                workbook = new XSSFWorkbook(inputStream);
            }
            return function.apply(workbook);
        } catch (IOException e) {
            throw e;
        }
    }

    /**
     * 获取sheet
     *
     * @param filePath
     * @return
     * @throws IOException
     */
    public List<String> getSheets(String filePath) throws IOException {
        List<String> listSheet = getWorkBook(filePath, (w) -> {
            List list = new ArrayList<>();
            for (int i = 0; i < w.getNumberOfSheets(); i++) {
                list.add(w.getSheetName(i));
            }
            return list;
        });
        return listSheet;
    }


    /**
     * 获取sheet中的行，未经解析
     *
     * @param filePath
     * @param sheetName
     */
    public List<List<Object>> getRows(String filePath, String sheetName,int beginRow) throws IOException {
        List<List<Object>> listRows = getWorkBook(filePath, (w) -> {
            Sheet sheet = w.getSheet(sheetName);
            List list = new ArrayList();
            DataFormatter dataFormatter = new DataFormatter();
            for (int i = beginRow; i <= sheet.getLastRowNum(); i++) {
                Row row = sheet.getRow(i);
                if(row!=null) {
                    List<Object> data = new ArrayList<>();
                    for (int j = 0; j < row.getPhysicalNumberOfCells(); j++) {
                        Cell cell = row.getCell(j);
                        if (cell != null) {
                            if (isDateCell(cell)) {
                                // 用于转化为日期格式
                                Date d = cell.getDateCellValue();
                                if (d != null) {
                                    DateFormat formater = new SimpleDateFormat("yyyy-MM-dd");
                                    data.add(formater.format(d));
                                }
                            } else {
                                try {
                                    switch (cell.getCellType()) {
                                        case _NONE:
                                        case BLANK:
                                        case ERROR:
                                        case FORMULA:
                                            data.add(null);
                                            break;
                                        case BOOLEAN:
                                            data.add(cell.getBooleanCellValue());
                                            break;
                                        case NUMERIC:
                                            data.add(dataFormatter.formatCellValue(cell));
                                            break;
                                        case STRING:
                                            data.add(cell.getStringCellValue().trim());
                                            break;
                                    }
                                } catch (Exception e) {
                                    data.add(null);
                                }
                            }
                        } else {
                            data.add(null);
                        }
                    }
                    if (isEmptyRow(data)) {
                        break;
                    } else {
                        list.add(data);
                    }
                }
            }
            return list;
        });
        return listRows;
    }


    /**
     * 是否是日期类型字段
     * @param currentCell
     * @return
     */
    private boolean isDateCell(Cell currentCell) {
        if ("yyyy/mm;@".equals(currentCell.getCellStyle().getDataFormatString())
                || "m/d/yy".equals(currentCell.getCellStyle().getDataFormatString())
                || "yy/m/d".equals(currentCell.getCellStyle().getDataFormatString())
                || "mm/dd/yy".equals(currentCell.getCellStyle().getDataFormatString())
                || "dd-mmm-yy".equals(currentCell.getCellStyle().getDataFormatString())
                || "yyyy/m/d".equals(currentCell.getCellStyle().getDataFormatString())) {
            if (DateUtil.isCellDateFormatted(currentCell)) {
               return true;
            }
        }
        return false;
    }

    /**
     * 是否空行
     * @param list
     * @return
     */
    private boolean isEmptyRow(List<Object> list){
        for (Object o : list) {
            if(o!=null){
                return false;
            }
        }
        return true;
    }

    /**
     * 将电子表内容转换成map，要求参数列表第一个是列名集合
     * @param list
     * @return
     */
    public List<Map<String,Object>> dataToMap(List<List<Object>> list){
        List<String> cols = list.get(0).stream().map(f->f.toString()).collect(Collectors.toList());
        List result = new ArrayList();
        for (int i = 1; i < list.size(); i++) {
            List<Object> row = list.get(i);
            Map<String,Object> map = new HashMap<>();
            for (int i1 = 0; i1 < row.size(); i1++) {
                map.put(cols.get(i1),row.get(i1));
            }
            result.add(map);
        }
        return result;
    }