Java註解--實現簡單讀取excel

實現工具類

利用註解實現簡單的excel數據讀取,利用註解對類的屬性和excel中的表頭映射,使用Apache的poi就不用在業務代碼中涉及row,rows這些屬性了。java

定義註解:app

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Excel {
  
    String name();

}

因爲本例中只涉及根據Excel表頭部分對Excel進行解析,只定義了一個name做爲和Excel表頭的隱射。工具

工具類完整代碼以下:this

public class ExcelUtil<T> {

    Class<T> clazz;

    public ExcelUtil(Class<T> clazz) {
        this.clazz = clazz;
    }

    public List<T> importExcel(String sheetName, InputStream input) {
        int maxCol = 0;
        List<T> list = new ArrayList<T>();
        try {
            Workbook workbook = WorkbookFactory.create(input);
            Sheet sheet = workbook.getSheet(sheetName);
            // 若是指定sheet名,則取指定sheet中的內容.
            if (!sheetName.trim().equals("")) {
                sheet = workbook.getSheet(sheetName);
            }
            // 若是傳入的sheet名不存在則默認指向第1個sheet.
            if (sheet == null) {
                sheet = workbook.getSheetAt(0);
            }
            int rows = sheet.getPhysicalNumberOfRows();
            // 有數據時才處理
            if (rows > 0) {
                List<Field> allFields = getMappedFiled(clazz, null);
                // 定義一個map用於存放列的序號和field.
                Map<Integer, Field> fieldsMap = new HashMap<Integer, Field>();
                // 第一行爲表頭
                Row rowHead = sheet.getRow(0);
                Map<String, Integer> cellMap = new HashMap<>();
                int cellNum = rowHead.getPhysicalNumberOfCells();
                for (int i = 0; i < cellNum; i++){
                    cellMap.put(rowHead.getCell(i).getStringCellValue().toLowerCase(), i);
                }
                for (Field field : allFields) {
                    // 將有註解的field存放到map中.
                    if (field.isAnnotationPresent(Excel.class)) {
                        Excel attr = field.getAnnotation(Excel.class);
                        // 根據Name來獲取相應的failed
                        int col = cellMap.get(attr.name().toLowerCase());
                        field.setAccessible(true);
                        fieldsMap.put(col, field);
                    }
                }
                // 從第2行開始取數據
                for (int i = 1; i < rows; i++) {
                    Row row = sheet.getRow(i);
                    T entity = null;
                    for (int j = 0; j < cellNum; j++) {
                        Cell cell = row.getCell(j);
                        if (cell == null) {
                            continue;
                        }
                        int cellType = cell.getCellType();
                        String c = "";
                        if (cellType == HSSFCell.CELL_TYPE_NUMERIC) {
                            DecimalFormat df = new DecimalFormat("0");
                            c = df.format(cell.getNumericCellValue());
                        } else if (cellType == HSSFCell.CELL_TYPE_BOOLEAN) {
                            c = String.valueOf(cell.getBooleanCellValue());
                        } else {
                            c = cell.getStringCellValue();
                        }
                        if (c == null || c.equals("")) {
                            continue;
                        }
                        entity = (entity == null ? clazz.newInstance() : entity);
                        // 從map中獲得對應列的field.
                        Field field = fieldsMap.get(j);
                        if (field == null) {
                            continue;
                        }
                        // 取得類型,並根據對象類型設置值.
                        Class<?> fieldType = field.getType();
                        if (String.class == fieldType) {
                            field.set(entity, String.valueOf(c));
                        } else if ((Integer.TYPE == fieldType)
                                || (Integer.class == fieldType)) {
                            field.set(entity, Integer.valueOf(c));
                        } else if ((Long.TYPE == fieldType)
                                || (Long.class == fieldType)) {
                            field.set(entity, Long.valueOf(c));
                        } else if ((Float.TYPE == fieldType)
                                || (Float.class == fieldType)) {
                            field.set(entity, Float.valueOf(c));
                        } else if ((Short.TYPE == fieldType)
                                || (Short.class == fieldType)) {
                            field.set(entity, Short.valueOf(c));
                        } else if ((Double.TYPE == fieldType)
                                || (Double.class == fieldType)) {
                            field.set(entity, Double.valueOf(c));
                        } else if (Character.TYPE == fieldType) {
                            if (c.length() > 0) {
                                field.set(entity, c.charAt(0));
                            }
                        }
                    }
                    if (entity != null) {
                        list.add(entity);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }


    /**
     * 獲得實體類全部經過註解映射了數據表的字段
     *
     * @param clazz
     * @param fields
     * @return
     */
    private List<Field> getMappedFiled(Class clazz, List<Field> fields) {
        if (fields == null) {
            fields = new ArrayList<Field>();
        }
        // 獲得全部定義字段
        Field[] allFields = clazz.getDeclaredFields();
        // 獲得全部field並存放到一個list中.
        for (Field field : allFields) {
            if (field.isAnnotationPresent(Excel.class)) {
                fields.add(field);
            }
        }
        if (clazz.getSuperclass() != null
                && !clazz.getSuperclass().equals(Object.class)) {
            getMappedFiled(clazz.getSuperclass(), fields);
        }

        return fields;
    }


}

代碼很簡單,獲取sheet,解析第一行,並和實體類標有註解的字段一一對應,用hashMap記錄下來,而後循環取得Excel中剩下全部的數據,根據map的對應關係將值set到對應字段。3d

基本使用

待解析表格以下:excel

定義實體類:code

public class User {

    @Excel(name = "filed1")
    private String name;
    @Excel(name = "filed2")
    private String nameEn;
    @Excel(name = "filed3")
    private Integer age;
    @Excel(name = "filed4")
    private String six;
    @Excel(name = "filed5")
    private String weight;

    // ...getter setter
}

使用工具類:orm

public static void main (String[] args) {
    FileInputStream fileInputStream = null;
    try {
        fileInputStream = new FileInputStream("D://data.xlsx");
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    ExcelUtil<User> util = new ExcelUtil<>(User.class);
    List<User> jalanHotelList = util.importExcel("user", fileInputStream);
    // do something
}

利用這個思路能夠擴展出導出excel功能,利用註解指定導出的excel表頭,甚至能夠輕鬆控制excel表頭的顏色,合併屬性等等,在xdemo中有詳細複雜的示例,能夠研究下。因爲個人需求很簡單,就不整那麼複雜啦。對象

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