POI獲取excel單元格的內容

重點是獲取日期格式。日期那列的單元格格式必須設置成日期纔有效，如果是以文本的形式爲日期的話，那麼要在getCellValue方法中的Cell.CELL_TYPE_STRING分支中做同樣的處理。

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class TestValue {
	public static void main(String[] args) {
		File file = new File("D:/test.xlsx");
		InputStream is = null;
		XSSFWorkbook wb = null;
		try {
			is = new FileInputStream(file);
			wb = new XSSFWorkbook(is);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		Sheet sheet = wb.getSheetAt(0);
		int num = sheet.getLastRowNum();
		for (int i = 0; i < num; i++) {
			Row row = sheet.getRow(i);
			int c = row.getLastCellNum();
			for (int j = 0; j < c; j++) {
				System.out.println(getCellValue(row.getCell(j)));				
			}
		}
		try {
			is.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	private static String getCellValue(Cell cell) {
		String value = "";
		int type = cell.getCellType();
		switch (type) {
		case Cell.CELL_TYPE_BOOLEAN:
			value = cell.getBooleanCellValue() + "";
			break;
		case Cell.CELL_TYPE_ERROR:
			value = "ERROR VALUE!";
			break;
		case Cell.CELL_TYPE_FORMULA:
			value = cell.getCellFormula() + "";
			break;
		case Cell.CELL_TYPE_NUMERIC:
			int SECONDS_PER_DAY = 86400;
			long DAY_MILLISECONDS = SECONDS_PER_DAY * 1000L;
			Double d = cell.getNumericCellValue();
			int wholeDays = (int)Math.floor(d);
	        int millisecondsInDay = (int)((d - wholeDays) * DAY_MILLISECONDS + 0.5);
	        Calendar calendar = new GregorianCalendar(); // 使用默認時區
	        setCalendar(calendar, wholeDays, millisecondsInDay, false);
	        SimpleDateFormat sdFormat = new SimpleDateFormat("yyyy-MM-dd");
	        SimpleDateFormat yearFormat = new SimpleDateFormat("yyyy");
	        Date date = calendar.getTime();
	        String year = yearFormat.format(date);
	        if (Integer.parseInt(year) > 1990) {
	        	value = sdFormat.format(date);				
			} else {
				value = d + "";
			}
			break;
		case Cell.CELL_TYPE_STRING:
			value = cell.getStringCellValue();
		}
		return value;
	}
	public static void setCalendar(Calendar calendar, int wholeDays,
            int millisecondsInDay, boolean use1904windowing) {
        int startYear = 1900;
        int dayAdjust = -1; // Excel 認爲 2/29/1900 是有效時間, 其實不是。
        if (use1904windowing) {
            startYear = 1904;
            dayAdjust = 1; // 1904 date windowing uses 1/2/1904 as the first day
        }
        else if (wholeDays < 61) {
            // 因爲excel中2/29/1900合法，所以優先使用3/1/1900
            // 如果 Excel 日期 == 2/29/1900, 在java中自動轉換成 3/1/1900 
            dayAdjust = 0;
        }
        calendar.set(startYear,0, wholeDays + dayAdjust, 0, 0, 0);
        calendar.set(GregorianCalendar.MILLISECOND, millisecondsInDay);
    }
}

excel中數據：

運行結果：