java导入导出Excel

首先导包

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>4.1.0</version>
</dependency>

创建 ExcelUtil.java

package com.example.util;

import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddress;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * Excel工具类
 */
public class ExcelUtil {

    /**
     * 导入 Excel 数据
     * @param filePath excel文件所在路径（一般先上传在读取）
     * @param fields 字段数组
     * @param startRowNum 从excel哪一行开始读
     * @return
     * @throws IOException
     */
    public static List<Map<String,Object>> read(String filePath, List<String> fields, int startRowNum) throws IOException {
        InputStream is = new FileInputStream(filePath);
        HSSFWorkbook hssfWorkbook = new HSSFWorkbook(is);
        List<Map<String,Object>> list = new ArrayList<>();
        // 循环工作表Sheet
        for (int numSheet = 0; numSheet < hssfWorkbook.getNumberOfSheets(); numSheet++) {
            HSSFSheet hssfSheet = hssfWorkbook.getSheetAt(numSheet);
            if (hssfSheet == null) {
                continue;
            }
            // 循环行Row
            for (int rowNum = startRowNum; rowNum <= hssfSheet.getLastRowNum(); rowNum++) {
                HSSFRow hssfRow = hssfSheet.getRow(rowNum);
                Map<String,Object> map = new HashMap<>();
                for (int i = 0,leng=fields.size(); i < leng; i++) {
                    map.put(fields.get(i),hssfRow.getCell(i));
                }
                list.add(map);
            }
        }
        return list;
    }

    /** 导出 Excel
     * @param title 标题
     * @param headers  表头
     * @param values  表中元素
     * @return
     */
    public static HSSFWorkbook getHSSFWorkbook(String title, String headers[], String [][] values){
        //创建一个HSSFWorkbook，对应一个Excel文件
        HSSFWorkbook hssfWorkbook = new HSSFWorkbook();
        //在workbook中添加一个sheet,对应Excel文件中的sheet
        HSSFSheet hssfSheet = hssfWorkbook.createSheet(title);
        //创建标题合并行
        hssfSheet.addMergedRegion(new CellRangeAddress(0,(short)0,0,(short)headers.length - 1));
        //设置标题样式
        HSSFCellStyle style = hssfWorkbook.createCellStyle();
        style.setAlignment(HorizontalAlignment.CENTER);   //设置居中样式
        style.setVerticalAlignment(VerticalAlignment.CENTER);
        //设置标题字体
        Font titleFont = hssfWorkbook.createFont();
        titleFont.setFontHeightInPoints((short) 14);
        style.setFont(titleFont);
        //设置值表头样式 设置表头居中
        HSSFCellStyle hssfCellStyle = hssfWorkbook.createCellStyle();
        hssfCellStyle.setAlignment(HorizontalAlignment.CENTER);   //设置居中样式
        hssfCellStyle.setBorderBottom(BorderStyle.THIN);
        hssfCellStyle.setBorderLeft(BorderStyle.THIN);
        hssfCellStyle.setBorderRight(BorderStyle.THIN);
        hssfCellStyle.setBorderTop(BorderStyle.THIN);
        //设置表内容样式
        //创建单元格，并设置值表头 设置表头居中
        HSSFCellStyle style1 = hssfWorkbook.createCellStyle();
        style1.setBorderBottom(BorderStyle.THIN);
        style1.setBorderLeft(BorderStyle.THIN);
        style1.setBorderRight(BorderStyle.THIN);
        style1.setBorderTop(BorderStyle.THIN);
        //产生标题行
        HSSFRow hssfRow = hssfSheet.createRow(0);
        HSSFCell cell = hssfRow.createCell(0);
        cell.setCellValue(title);
        cell.setCellStyle(style);
        //产生表头
        HSSFRow row1 = hssfSheet.createRow(1);
        for (int i = 0; i < headers.length; i++) {
            HSSFCell hssfCell = row1.createCell(i);
            hssfCell.setCellValue(headers[i]);
            hssfCell.setCellStyle(hssfCellStyle);
        }
        //创建内容
        for (int i = 0; i <values.length; i++){
            row1 = hssfSheet.createRow(i +2);
            for (int j = 0; j < values[i].length; j++){
                //将内容按顺序赋给对应列对象
                HSSFCell hssfCell = row1.createCell(j);
                hssfCell.setCellValue(values[i][j]);
                hssfCell.setCellStyle(style1);
            }
        }
        return hssfWorkbook;
    }
}

使用方式：

package com.example.controller;


import com.example.util.ExcelUtil;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;
import java.util.Map;


@RestController
public class TestController {
    // 导入 excel 读取数据
    public static void main(String[] args) {
        // 先上传 excel 然后在读取数据
        String path = "D:\\upload\\2020\\03\\19\\8aa9eb5d886a4dc6bc7f091137c01084.xls";
        String[] fields = {"id","name","password","phone","time"};
        try {
            List<Map<String, Object>> result = ExcelUtil.read(path, Arrays.asList(fields),2);
            System.out.println(result);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 导出 excel
     * @param request
     * @param response
     * @throws Exception
     */
    @RequestMapping(value = "/export")
    @ResponseBody
    public void export(HttpServletRequest request, HttpServletResponse response) throws Exception {
        //获取数据
        List<PageData> list = new ArrayList<>();
        Date date = new Date();
        for (int i = 0; i < 10; i++) {
            PageData pageData = new PageData();
            pageData.setId("00"+i);
            pageData.setUsername("小池" + i);
            pageData.setPassword("123"+i);
            pageData.setCreateTime(date);
            pageData.setPhone("135"+i);
            list.add(pageData);
        }

        //excel标题
        String[] headers = {"用户ID", "用户名称", "用户密码", "用户手机","创建时间"};

        //excel文件名
        String fileName = "用户信息表" + System.currentTimeMillis() + ".xls";

        //excel sheet名
        String title = "用户信息表";

        String [][] content = new String[list.size()][5];
        for (int i = 0; i < list.size(); i++) {
            content[i] = new String[headers.length];
            PageData obj = list.get(i);
            content[i][0] = obj.getId().toString();
            content[i][1] = obj.getUsername();
            content[i][2] = obj.getPassword();
            content[i][3] = obj.getPhone();
            content[i][4] = obj.getCreateTime().toString();
        }
        //创建HSSFWorkbook
        HSSFWorkbook wb = ExcelUtil.getHSSFWorkbook(title, headers, content);
        //响应到客户端
        try {
            // 设置响应头信息
            this.setResponseHeader(response, fileName);
            OutputStream os = response.getOutputStream();
            wb.write(os);
            os.flush();
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 发送响应流方法
     */
    public void setResponseHeader(HttpServletResponse response, String fileName) {
        try {
            try {
                fileName = new String(fileName.getBytes(), "ISO8859-1");
            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            response.setContentType("application/octet-stream;charset=ISO8859-1");
            response.setHeader("Content-Disposition", "attachment;filename=" + fileName);
            response.addHeader("Pargam", "no-cache");
            response.addHeader("Cache-Control", "no-cache");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}