poi实现excel数据的导入和导出

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1、需要的jar包

 <dependency>
     <groupId>org.apache.poi</groupId>
     <artifactId>poi</artifactId>
     <version>3.14</version>
 </dependency>
 <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
       <version>3.14</version>
 </dependency>

2、工具包，可根据实际业务调整工具包

package com.jbf.util;

import org.apache.poi.hssf.usermodel.*;
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.ss.usermodel.Workbook;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletResponse;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;

/*********************************
 * 类描述：
 * @author huangsz
 * @date 2019/11/21
 * @version v1.0
 **********************************/
public class ExcelUtil {

    public static void main(String[] args) throws Exception{
    }

    public static void exportExcel(HttpServletResponse response,
                                   String title, String subheading,
                                   List<String> header,
                                   List<List<String>> dataList) throws Exception {
        // 创建工作簿
        HSSFWorkbook workbook = new HSSFWorkbook();
        // 创建行
        HSSFCellStyle cellStyle = workbook.createCellStyle();
        // 居中
        cellStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        // 创建一个sheet
        HSSFSheet sheet = workbook.createSheet("sheet名字");
        // 创建一个标题
        CellRangeAddress cellRangeAddress = new CellRangeAddress(0, 0, 0, header.size());
        // 创建一个副标题
        CellRangeAddress cellRangeAddress2 = new CellRangeAddress(1, 1, 0, header.size());
        sheet.addMergedRegion(cellRangeAddress);
        sheet.addMergedRegion(cellRangeAddress2);

        // 标题，居中
        HSSFRow row0 = sheet.createRow(0);
        HSSFCell cell0 = row0.createCell(0);
        cell0.setCellValue(title);
        cell0.setCellStyle(cellStyle);

        // 第一行
        HSSFRow row1 = sheet.createRow(1);
        HSSFCell cell1 = row1.createCell(0);
        // 副标题
        cell1.setCellValue(subheading);
        cell1.setCellStyle(cellStyle);

        // 表头
        HSSFRow row = sheet.createRow(2);
        HSSFCell cell = null;
        for (int i = 0; i < header.size(); i++) {
            cell =  row.createCell(i);
            cell.setCellValue(header.get(i));
            cell.setCellStyle(cellStyle);
        }

        // 数据
        for (int i = 0; i < dataList.size(); i++) {
            row = sheet.createRow(i + 3);
            for (int j = 0; j < dataList.get(i).size(); j++) {
                row.createCell(j).setCellValue(dataList.get(i).get(j));
            }
        }

        OutputStream out = response.getOutputStream();
        // 设置页面不缓存
        response.reset();
        String fileName = URLEncoder.encode(title, "UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xls");
        response.setContentType("application/msexcel");
        workbook.write(out);
        out.close();
    }

    /**
     *  导入数据
     * @param file 表
     * @param sheetIndex sheet索引值
     * @param headerIndex 表头的索引（用于获取共多少列以及第几行开始读数据）
     * @return
     * @throws Exception
     */
    public static List<List<Object>> importExcel(MultipartFile file, int sheetIndex, int headerIndex) throws Exception {
        List<List<Object>> data = new ArrayList<>();
        Workbook workbook = getWorkbook(file);
        // 导入某页sheet
        if (sheetIndex >-1) {
            Sheet sheet = workbook.getSheetAt(sheetIndex);
            List<List<Object>> lists = importSheet(sheet, headerIndex);
            data.addAll(lists);
        } else {
            // 导入全部
            //导入全部
            for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
                Sheet sheet = workbook.getSheetAt(i);
                if (sheet == null) {
                    continue;
                }
                List<List<Object>> lists = importSheet(sheet, headerIndex);
                data.addAll(lists);
            }
        }
        return data;
    }

    private static List<List<Object>> importSheet(Sheet sheet, int headerIndex) throws Exception {
        List<List<Object>> data = new ArrayList<>();
        // 获取行数
        int row = sheet.getLastRowNum();
        //row = -1 表格中没有数据
        //row = headerIndex 表格中表头以下没有数据（指没有有用数据）
        if (row == -1 || row == headerIndex) {
            throw new Exception("表格中没有有用数据!");
        }
        // 获取列数
        int columnNum = sheet.getRow(headerIndex).getPhysicalNumberOfCells();
        // 从表头下一行开始取数据
        for (int i = headerIndex + 1; i <= row; i++) {
            Row row1 = sheet.getRow(i);
            List<Object> list = new ArrayList<>();
            if (row1 != null) {
                for (int j = 0; j < columnNum; j++) {
                    list.add(getCellValue(row1.getCell(j)));
                }
            }
            data.add(list);
        }
        return data;
    }

    private static Object getCellValue(Cell cell) {
        String cellValue = "";
        DecimalFormat df = new DecimalFormat("#");
        switch (cell.getCellType()) {
            case HSSFCell.CELL_TYPE_STRING:
                cellValue = cell.getRichStringCellValue().getString().trim();
                break;
            case HSSFCell.CELL_TYPE_NUMERIC:
                cellValue = df.format(cell.getNumericCellValue());
                break;
            case HSSFCell.CELL_TYPE_BOOLEAN:
                cellValue = String.valueOf(cell.getBooleanCellValue()).trim();
                break;
            case HSSFCell.CELL_TYPE_FORMULA:
                cellValue = cell.getCellFormula();
                break;
            default:
                cellValue = "";
        }
        return cellValue.trim();
    }


    private static Workbook getWorkbook(MultipartFile file) throws Exception{
        Workbook workbook = null;
        String xls = "xls";
        String xlsx = "xlsx";
        // 获取文件名
        String fileName = file.getOriginalFilename();
        if (fileName.endsWith(xls)) {
            workbook = new HSSFWorkbook(file.getInputStream());
        } else if(fileName.endsWith(xlsx)){
            workbook = new XSSFWorkbook(file.getInputStream());
        } else {
            throw new Exception("文件格式有误!");
        }
        return workbook;
    }
}

3、验证

@GetMapping("/exe")
    public void excel(HttpServletResponse response) {
        List<String> header = new ArrayList<>();
        header.add("评论Id");
        header.add("被评论人Id");
        header.add("内容");
        TestBean bean = new TestBean();
        List<List<String>> dataList = new ArrayList<>();
        for (int i = 1; i <= 5; i++) {
            List<String> data = new ArrayList<>();
            data.add(i+"");
            data.add(i+1+"");
            data.add("第" + i + "条评论");
            dataList.add(data);
        }
        try {
            ExcelUtil.exportExcel(response,"标题","副标题",header,dataList);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @PostMapping("/up")
    public void upload(@RequestParam("file") MultipartFile file){
        try {
            List<List<Object>> lists = ExcelUtil.importExcel(file, 0,2);
            System.out.println(lists.size());
            for (List<Object> list : lists) {
                for (Object o : list) {
                    System.out.println(o);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }