Java读写Excel文件，利用POI

直接看工具类代码吧，

package com.example.demo.util;

import com.example.demo.entity.ExcelDataVO;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.BorderStyle;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.VerticalAlignment;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.ss.util.RegionUtil;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * Excel文档工具类
 */
public class ExcelReader {
     //文件写入需要注意
    /**
     * 把数据写入到Excel文件
     * @param fileName 自动生成的Excel文件的全路径文件名称
     * @param excelDataVo 要写入到Excel文件中的数据
     */
    public static void writeExcel(String fileName, List<ExcelDataVO> excelDataVo) throws IOException {
        Workbook workbook = null;
        Sheet sheet = null;
        Row row = null;
        Cell cell = null;

        //创建Excel文件
        File excelFile = new File(fileName.trim());

        //创建Excel工作薄
        if (excelFile.getName().endsWith("xlsx")) {
            workbook = new XSSFWorkbook();
        } else {
            workbook = new HSSFWorkbook();
        }

        //创建Excel表单
        sheet = workbook.createSheet();

        //设置列宽，宽度为256的整数倍
        sheet.setColumnWidth(1, 5120);
        sheet.setColumnWidth(2, 3840);
        sheet.setColumnWidth(3, 2560);
        sheet.setColumnWidth(4, 2560);
        sheet.setColumnWidth(5, 5120);

        //设置默认行高(默认为300)
        sheet.setDefaultRowHeight((short) 512);

        //设置合并单元格
        CellRangeAddress titleCellAddresses = new CellRangeAddress(1,2,1,5);
        sheet.addMergedRegion(titleCellAddresses);

        //创建标题行
        row = sheet.createRow(1);
        cell = row.createCell(1, CellType.STRING);
        cell.setCellStyle(getTitleCellStyle(workbook));
        cell.setCellValue("User信息表格");

        //设置合并单元格的边框，这个需要放在创建标题行之后
        setRegionBorderStyle(BorderStyle.THIN, titleCellAddresses, sheet);

        //创建表头行
        row = sheet.createRow(3);
        cell = row.createCell(1, CellType.STRING);
        cell.setCellStyle(getHeaderCellStyle(workbook));
        cell.setCellValue("ID");
        cell = row.createCell(2, CellType.STRING);
        cell.setCellStyle(getHeaderCellStyle(workbook));
        cell.setCellValue("姓名");
        cell = row.createCell(3, CellType.STRING);
        cell.setCellStyle(getHeaderCellStyle(workbook));
        cell.setCellValue("性别");
        cell = row.createCell(4, CellType.STRING);
        cell.setCellStyle(getHeaderCellStyle(workbook));
        cell.setCellValue("年龄");
        cell = row.createCell(5, CellType.STRING);
        cell.setCellStyle(getHeaderCellStyle(workbook));
        cell.setCellValue("生日");

        //创建表体行
        for(int i = 0; i < excelDataVo.size(); i++) {
            row = sheet.createRow(i + 4);
            cell = row.createCell(1, CellType.NUMERIC);
            cell.setCellStyle(getBodyCellStyle(workbook));
            cell.setCellValue(excelDataVo.get(i).getItemId());
            cell = row.createCell(2, CellType.STRING);
            cell.setCellStyle(getBodyCellStyle(workbook));
            cell.setCellValue(excelDataVo.get(i).getItemName());
            cell = row.createCell(3, CellType.STRING);
            cell.setCellStyle(getBodyCellStyle(workbook));
            cell.setCellValue(excelDataVo.get(i).getStorename());
        }

        //把Excel工作薄写入到Excel文件
        FileOutputStream os = new FileOutputStream(excelFile);
        workbook.write(os);
        os.flush();
        os.close();
    }

    /**
     * 从Excel文件读取数据
     * @param fileName 要读取的Excel文件的全路径文件名称
     * @return 从Excel文件中批量导入的用户数据
     */
    public static String[] readExcel(String fileName) throws IOException {
        Workbook workbook = null;
        Sheet sheet = null;
        Row row = null;

        //读取Excel文件
        File excelFile = new File(fileName.trim());
        InputStream is = new FileInputStream(excelFile);

        //获取Excel工作薄
        if (excelFile.getName().endsWith("xlsx")) {
            workbook = new XSSFWorkbook(is);
        } else {
            workbook = new HSSFWorkbook(is);
        }
        if (workbook == null) {
            System.err.println("Excel文件有问题,请检查！");
            return null;
        }
        String[] lines = new String[1000000];
        //获取Excel表单
        sheet = workbook.getSheetAt(0);
        int rowNum = 1;
        for(; rowNum <= sheet.getLastRowNum(); rowNum++) {
            //获取一行
            row = sheet.getRow(rowNum);
            ExcelDataVO edv = new ExcelDataVO();
            System.out.println("获取一行"+row.getCell(0));
            System.out.println("获取一行"+row.getCell(1));
            System.out.println("获取一行"+row.getCell(2));
            lines[rowNum]+=row.getCell(0)+"#"+row.getCell(1)+"#"+row.getCell(2);
            if(lines[rowNum]==null && lines[rowNum].equals("")){
                break;
            }
        }
        String[] lines2 = new String[rowNum];
        for(int i=0;i<rowNum;i++){
            lines2[i] = lines[i];
            System.out.println(lines2[i]);
        }
        return lines2;
    }

    /**
     * 设置合并单元格的边框
     * @param style 要设置的边框的样式
     * @param cellAddresses 要设置的合并的单元格
     * @param sheet 要设置的合并的单元格所在的表单
     */
    private static void setRegionBorderStyle(BorderStyle style, CellRangeAddress cellAddresses, Sheet sheet) {
        RegionUtil.setBorderTop(style, cellAddresses, sheet);
        RegionUtil.setBorderBottom(style, cellAddresses, sheet);
        RegionUtil.setBorderLeft(style, cellAddresses, sheet);
        RegionUtil.setBorderRight(style, cellAddresses, sheet);
    }

    /**
     * 设置普通单元格的边框
     * @param style 要设置的边框的样式
     * @param cellStyle 单元格样式对象
     */
    private static void setCellBorderStyle(BorderStyle style, CellStyle cellStyle) {
        cellStyle.setBorderTop(style);
        cellStyle.setBorderBottom(style);
        cellStyle.setBorderLeft(style);
        cellStyle.setBorderRight(style);
    }

    /**
     * 设置标题单元格样式
     * @param workbook 工作薄对象
     * @return 单元格样式对象
     */
    private static CellStyle getTitleCellStyle(Workbook workbook) {
        CellStyle cellStyle = workbook.createCellStyle();

        //设置字体
        Font font = workbook.createFont();
        font.setFontName("黑体");
        font.setFontHeightInPoints((short) 24);
        font.setColor((short) 10);
        cellStyle.setFont(font);

        //设置文字居中显示
        cellStyle.setAlignment(HorizontalAlignment.CENTER);
        cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);

        return cellStyle;
    }

    /**
     * 设置表头单元格样式
     * @param workbook 工作薄对象
     * @return 单元格样式对象
     */
    private static CellStyle getHeaderCellStyle(Workbook workbook) {
        CellStyle cellStyle = workbook.createCellStyle();

        //设置字体
        Font font = workbook.createFont();
        font.setFontName("宋体");
        font.setFontHeightInPoints((short) 20);
        font.setBold(true);
        cellStyle.setFont(font);

        //设置文字居中显示
        cellStyle.setAlignment(HorizontalAlignment.CENTER);
        cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);

        //设置单元格的边框
        setCellBorderStyle(BorderStyle.THIN, cellStyle);

        return cellStyle;
    }

    /**
     * 设置表体单元格样式
     * @param workbook 工作薄对象
     * @return 单元格样式对象
     */
    private static CellStyle getBodyCellStyle(Workbook workbook) {
        CellStyle cellStyle = workbook.createCellStyle();

        //设置字体
        Font font = workbook.createFont();
        font.setFontName("宋体");
        font.setFontHeightInPoints((short) 16);
        cellStyle.setFont(font);

        //设置文字居中显示
        cellStyle.setAlignment(HorizontalAlignment.CENTER);
        cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);

        //设置单元格的边框
        setCellBorderStyle(BorderStyle.THIN, cellStyle);

        return cellStyle;
    }

    /**
     * 获取单元格的值的字符串
     * @param cell 单元格对象
     * @return cell单元格的值的字符串
     */
    private static String getStringValue(Cell cell) {
        if (cell == null) {
            return null;
        }
        CellType cellType = cell.getCellType();
        switch (cellType) {
            case STRING:
                return cell.getStringCellValue();
            case NUMERIC:
                double value = cell.getNumericCellValue();
                return String.valueOf(Math.round(value));
            case BOOLEAN:
                return String.valueOf(cell.getBooleanCellValue());
            default:
                return null;
        }
    }

}