下载并导入项目【poi.3.17.jar】

strust.xml

<action name="returnLate_*" class="com.stureturnlate.moudels.biz.action.return_late.ReturnLateAction" method="{1}">
            <result name="list">/page/moudels/biz/return_late/returnLateList.jsp</result>
            <result name="openAdd">/page/moudels/biz/return_late/returnLateAdd.jsp</result>
            <!--<result name="openEdit">/page/biz/student/studentUpdate.jsp</result>-->
            <result name="openDetails">/page/moudels/biz/return_late/returnLateDetails.jsp</result>

            <!-- 导出Excel -->
            <result name="download" type="stream">
                <param name="contentType">application/vnd.ms-excel</param><!-- 注意这里的ContentType -->
                <param name="contentDisposition">attachment;filename="${fileName}.xls"</param><!-- 下载文件的名字 -->
                <param name="bufferSize">1024</param><!-- 下载文件的大小 1048576=1M -->
                <param name="inputName">excelFile</param><!-- 这里需要和Action里的变量名一致 -->
            </result>
        </action>

ReturnLateAction.class

    /**
     * 导出
     * @return
     */
    public String download() throws Exception  {

        List<ReturnLateEntity> returnLateEntityList = new ArrayList<>();
        fileName = fileName+ DateTool.dateFormat(new Date());
        fileName=new String(fileName.getBytes("gb2312"), "iso8859-1");//防止中文乱码或不显示
//TODO 第一步：声明excel的文档对象
        HSSFWorkbook returnLateExcel;
        try {
            //查询的结果，插入Excel填充数据
            String[] ids = returnLateIds.split(",");
            returnLateEntityList = returnLateService.selectAllReturnLate(ids);

            //TODO 第二步：获取excel的文档对象
            returnLateExcel = CreateExcel.createReturnLateExcel(returnLateEntityList);

            ByteArrayOutputStream output = new ByteArrayOutputStream();//字节数组输出流

            //TODO 第三步：写入字节数组输出流
            returnLateExcel.write(output);
            byte[] ba = output.toByteArray();

            //TODO 第四步：为输入流对象赋值
            excelFile = new ByteArrayInputStream(ba);

            output.flush();
            output.close();//关闭
        } catch (SQLException e) {
            System.out.println("晚归记录文件内容写入或者创建失败失败！");
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return "download";
    }

文件导出类CreateExcel.class

package com.stureturnlate.common;

import com.stureturnlate.moudels.vo.*;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.ss.usermodel.HorizontalAlignment;

import java.sql.SQLException;
import java.util.List;

/**
 * @author soldier
 * @title: CreateExcel
 * @projectName stu_return_late
 * @description: 文件导出Excel
 * @date 19-6-10下午9:56
 */
public class CreateExcel {

    public static HSSFWorkbook createReturnLateExcel(List<ReturnLateEntity> returnLateEntityList) throws SQLException {
        // 创建一个Excel文件
        HSSFWorkbook workbook = new HSSFWorkbook();//excel的文档对象
        // 创建一个工作表
        HSSFSheet sheet = workbook.createSheet("学生晚归记录");
        // 添加表头行
        HSSFRow hssfRow = sheet.createRow(0);
        // 设置单元格格式居中
        HSSFCellStyle cellStyle = workbook.createCellStyle();
        cellStyle.setAlignment(HorizontalAlignment.CENTER);

        int index = 0;
        // 添加表头内容
        HSSFCell headCell = hssfRow.createCell(index++);
        headCell.setCellValue("晚归编号");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("晚归学生");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("所属学院");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("学生所在宿舍");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("晚归时间");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("晚归原因");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index++);
        headCell.setCellValue("记录者工号");
        headCell.setCellStyle(cellStyle);

        headCell = hssfRow.createCell(index);
        headCell.setCellValue("记录者姓名");
        headCell.setCellStyle(cellStyle);

        // 添加数据内容
        for (int i = 0; i < returnLateEntityList.size(); i++) {
            hssfRow = sheet.createRow((int) i + 1);
            ReturnLateEntity returnLateEntity = returnLateEntityList.get(i);

            index = 0;
            // 创建单元格，并设置值
            HSSFCell cell = hssfRow.createCell(index++);
            cell.setCellValue(returnLateEntity.getReturnLateId());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            StudentEntity studentEntity = new StudentEntity();//获取学生名称
            cell.setCellValue(studentEntity.getStudentName());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            CollegeEntity collegeEntity = new CollegeEntity();//获取学院
            cell.setCellValue(collegeEntity.getCollegeName());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            HostelEntity hostelEntity = new HostelEntity();//获取宿舍名称
            cell.setCellValue(hostelEntity.getHostelName());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            cell.setCellValue(DateTool.dateTimeFormat(returnLateEntity.getReturnLateTime()));
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            cell.setCellValue(returnLateEntity.getReturnLateCause());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index++);
            DormMasterEntity dormMasterEntity = new DormMasterEntity();
            cell.setCellValue(dormMasterEntity.getDormMasterId());
            cell.setCellStyle(cellStyle);

            cell = hssfRow.createCell(index);
            cell.setCellValue(dormMasterEntity.getDormMasterName());
            cell.setCellStyle(cellStyle);
        }

        try {
            return workbook;

        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}