java利用注解实现简单的excel数据读取

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

}

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);
   // 如果指定sheet名,则取指定sheet中的内容.
   if (!sheetName.trim().equals("")) {
    sheet = workbook.getSheet(sheetName);
   }
   // 如果传入的sheet名不存在则默认指向第1个sheet.
   if (sheet == null) {
    sheet = workbook.getSheetAt(0);
   }
   int rows = sheet.getPhysicalNumberOfRows();
   // 有数据时才处理
   if (rows > 0) {
    List<Field> allFields = getMappedFiled(clazz, null);
    // 定义一个map用于存放列的序号和field.
    Map<Integer, Field> fieldsMap = new HashMap<Integer, Field>();
    // 第一行为表头
    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) {
     // 将有注解的field存放到map中.
     if (field.isAnnotationPresent(Excel.class)) {
      Excel attr = field.getAnnotation(Excel.class);
      // 根据Name来获取相应的failed
      int col = cellMap.get(attr.name().toLowerCase());
      field.setAccessible(true);
      fieldsMap.put(col, field);
     }
    }
    // 从第2行开始取数据
    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);
      // 从map中得到对应列的field.
      Field field = fieldsMap.get(j);
      if (field == null) {
       continue;
      }
      // 取得类型,并根据对象类型设置值.
      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;
 }


 /**
  * 得到实体类所有通过注解映射了数据表的字段
  *
  * @param clazz
  * @param fields
  * @return
  */
 private List<Field> getMappedFiled(Class clazz, List<Field> fields) {
  if (fields == null) {
   fields = new ArrayList<Field>();
  }
  // 得到所有定义字段
  Field[] allFields = clazz.getDeclaredFields();
  // 得到所有field并存放到一个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;
 }


}

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
}

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
}