poi读取Excel日期为数字的解决方法

这个问题虽然也比较常见，解决办法也比较简单，但是网上有一些代码不全，思路混乱，乱七八糟的办法，容易误导大家，特地来为大家开路

这里分享一下我的一个思路

Maven依赖

<!--POI-->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>3.9</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>3.9</version>
</dependency>
<!--fastjson-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.60</version>
</dependency>

date.xlsx

excel的格式如下图

id	date
A	2020-12-01
B	2020-12-02
C	2020-05-03
D	2020-07-04
E	2020-11-05
F	2020-09-06
G	2020-12-07
H	2020-12-08

ConvertExcelDate.java

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import org.apache.poi.ss.usermodel.*;

import java.io.FileInputStream;
import java.text.SimpleDateFormat;
import java.util.Date;


/**
 * @Author Daniel
 * @Description 解决poi读取excel日期为数字的问题
 **/

public class ConvertExcelDate {


    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("date.xlsx");
            Workbook workbook = WorkbookFactory.create(fis);
            // 获取第一张表
            Sheet sheet = workbook.getSheetAt(0);
            // 获取行数
            int rows = sheet.getPhysicalNumberOfRows();
            // 获取第一行的表头
            Row firstRow = sheet.getRow(0);
            // 获取列数
            JSONArray jsonArray = new JSONArray();
            // i=1，忽略表头
            for (int i = 1; i < rows; i++) {
                Row row = sheet.getRow(i);
                if (row != null) {
                    JSONObject rowObj = new JSONObject();
                    //循环列
                    for (int j = 0; j < firstRow.getPhysicalNumberOfCells(); j++) {
                        Cell cellData = row.getCell(j);
                        if (cellData != null) {
                            // 日期会被当作数字
                            if (cellData.getCellType() == Cell.CELL_TYPE_NUMERIC) {
                                // 设置要求的日期格式
                                SimpleDateFormat sdf = new SimpleDateFormat("MM/d/yyyy");
                                // 拿到数字格式的日期
                                double value = cellData.getNumericCellValue();
                                // 这里的关键就是使用DateUtil类将数字转化为日期
                                Date date = DateUtil.getJavaDate(value);
                                rowObj.put(firstRow.getCell(j).getStringCellValue(), sdf.format(date));

                            } else {
                                row.getCell(j).setCellType(Cell.CELL_TYPE_STRING);
                                rowObj.put(firstRow.getCell(j).getStringCellValue(), cellData.getStringCellValue());
                            }
                        } else {
                            rowObj.put(firstRow.getCell(j).getStringCellValue(), "");
                        }
                    }
                    jsonArray.add(rowObj);

                }
            }
            System.out.println(jsonArray);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出结果

[
  {
    "date": "12/1/2020",
    "id": "A"
  },
  {
    "date": "12/2/2020",
    "id": "B"
  },
  {
    "date": "05/3/2020",
    "id": "C"
  },
  {
    "date": "07/4/2020",
    "id": "D"
  },
  {
    "date": "11/5/2020",
    "id": "E"
  },
  {
    "date": "09/6/2020",
    "id": "F"
  },
  {
    "date": "12/7/2020",
    "id": "G"
  },
  {
    "date": "12/8/2020",
    "id": "H"
  }
]