@[toc]

一、业务背景

业务需求：从数据库查询多个list集合信息封装excel，每个excel都有2个sheet页，填充不同的信息，最后将所有excel打包成zip文件，以流的形式返回给客户端，供客户端另存为窗口下载。

1. 只发出一次请求
2. 每个excel表中到数据记录不能超过2条
3. excel文件或者zip包不会上传服务器，而是查询后直接封装excel，然后把多个excel封装成zip包直接返回

之前看过其他人的方案大概有2种：

方案1：打包成zip包后上传到服务器某个路径下，然后在读取该路径的zip文件，以流的形式返回给客户端。
方案2：不上传服务器，而是查询后直接封装excel，然后把多个excel封装成zip包直接返回。（本人采用的就是第二种方案）

最终的效果，如图

二、实现思路

1. 设置HttpServletResponse的参数，比如header、contentType
2. 新建一个Workbook对象并置为空，同时初始化相关对象，比如List、File等
3. 从数据库查询多条list
4. 以其中为主的一个list计算分页数量
5. 循环遍历list开始
6. 初始化新的Workbook对象，并设置相应的Title
7. 将list拆分成多个段，分别写到的Workbook对象中
8. 将Workbook对象填充到List<XSSFWorkbook>中
9. 重复步骤6至步骤8直至写完所有数据
10. 最后统一封装zip压缩包并导出，调用downFileByStream方法
11. 初始化ZipOutputStream对象
12. 循环遍历List<XSSFWorkbook>将每一个wb写入ZipOutputStream对象中，并将内存流写入Zip文件，即：将每一个excel封装到zip包中
13. 关闭ZipOutputStream

二、准备工作

1.准备data模板.xlsx

2.引入poi相关依赖，用于操作excel

pom.xml

<dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.17</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.17</version>
</dependency>

3.针对WorkBook+ZIP压缩输入/输出流，相关方法知识点要有所了解

Apache POI包中的HSSFWorkbook、XSSFWorkbook、SXSSFWorkbook的区别如下:

ZipOutputStream类的常用方法如下表所示：

ZipInputStream类的常用方法如下表所示：

Workbook类提供的方法

三、完整的项目代码

ExportUtil工具类

package com.excel.utils;

import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

/**
 * 导出【用户、组、隶属关系】工具
 * @Author 211145187
 * @Date 2023/4/13 16:29
 **/
public class ExportUtil {
    private static Logger logger = LoggerFactory.getLogger(ExportUtil.class);

    /**
     * 自定义获取分页总页数的方法
     * @param count 查询集合数量
     * @param pageSize 配置文件中设置的单文件存储最大条数
     * @return 总页数
     */
    public static Integer getPageCount(Integer count, Integer pageSize){
        Integer pageCount = 0;
        if(count.equals(0)){
            return pageCount;
        }
        pageCount = count/pageSize;
        if(count % pageSize != 0){
            pageCount++;
        }

        return pageCount;
    }

    /**
     * 自定义List分页工具
     * @param list 待分页的list数据
     * @param pageNum 页码
     * @param pageSize 页容量
     * @param pageCount 总页数
     * @return 分页后的list数据
     */
    public static <T> List<T> getPageList(List<T> list, Integer pageNum, Integer pageSize, Integer pageCount){

        /**开始索引*/
        int beginIndex = 0;
        /**结束索引*/
        int endIndex = 0;

        Integer compare = pageNum.compareTo(pageCount);
        if(!compare.equals(0)){
            beginIndex = (pageNum - 1) * pageSize;
            endIndex = beginIndex + pageSize;
        }else{
            beginIndex = (pageNum - 1) * pageSize;
            endIndex = list.size();
        }
        List pageList = list.subList(beginIndex, endIndex);

        return pageList;
    }

    /**
     * HSSFWorkbook转file
     * @param wb wb
     * @param name 文件名称
     * @return File
     */
    public static File xssfWorkbookToFile(Workbook wb, String name) {
        File toFile = new File(name);
        try {
            OutputStream os = new FileOutputStream(toFile);
            wb.write(os);
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return toFile;
    }


    /**
     * 直接下载zip包
     * @param response response
     * @param excels wb集合
     */
    public static void downFileByStream(HttpServletResponse response, List<XSSFWorkbook> excels){
        try {
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            ZipOutputStream zipOutputStream = new ZipOutputStream(toClient);
            for(int i=0; i<excels.size(); i++){
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                // 将Workbook写入内存流
                excels.get(i).write(baos);
                ZipEntry zipEntry = new ZipEntry("data" + i + ".xlsx");
                zipOutputStream.putNextEntry(zipEntry);
                // 将内存流写入Zip文件
                zipOutputStream.write(baos.toByteArray());
            }
            zipOutputStream.closeEntry();
            zipOutputStream.flush();
            zipOutputStream.close();
        }catch (Exception e){
            logger.error("downFileByStream==========fail:{}", e.getMessage());
        }
    }
}

application.properties

server.port=8001
#导出excel配置，单文件存储最大数量
export.num=2

OperateExcelController

package com.excel.controller;

import com.excel.bean.Score;
import com.excel.bean.Teacher;
import com.excel.utils.ExportUtil;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.FillPatternType;
import org.apache.poi.ss.usermodel.IndexedColors;
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.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * 测试3.17版本操作Excel
 * @Author 211145187
 * @Date 2022/2/22 19:43
 **/
@RequestMapping("/excel")
@Controller
public class OperateExcelController {
	private static Logger logger = LoggerFactory.getLogger(OperateExcelController.class);
    @Value("${export.num:10000}")
    private Integer exportLimitNum;

    //构建教师集合数据
    public List<Teacher> buildTeacherList1() {
        List<Teacher> teacherList = new ArrayList<>();
        Teacher teacher1 = new Teacher();
        teacher1.setName("周杰伦");
        teacher1.setClasses("三年二班");
        teacher1.setCollege("魔法学院");
        teacher1.setAlias("Jay Chou");
        teacherList.add(teacher1);
        Teacher teacher2 = new Teacher();
        teacher2.setName("陈奕迅");
        teacher2.setClasses("三年二班");
        teacher2.setCollege("魔法学院");
        teacher2.setAlias("Eason");
        teacherList.add(teacher2);
        Teacher teacher3 = new Teacher();
        teacher3.setName("林俊杰");
        teacher3.setClasses("三年二班");
        teacher3.setCollege("魔法学院");
        teacher3.setAlias("Eason");
        teacherList.add(teacher3);
        Teacher teacher4 = new Teacher();
        teacher4.setName("张杰");
        teacher4.setClasses("三年二班");
        teacher4.setCollege("魔法学院");
        teacher4.setAlias("Eason");
        teacherList.add(teacher4);
        return teacherList;
    }
    //构建分数集合数据
    public List<Score> buildScoreList1() {
        List<Score> scoreList = new ArrayList<>();
        Score score1 = new Score();
        score1.setName("流川枫");
        score1.setClasses("三年二班");
        score1.setWriteScore("6");
        score1.setComputerScore("4");
        scoreList.add(score1);
        Score score2 = new Score();
        score2.setName("樱木花道");
        score2.setClasses("三年二班");
        score2.setWriteScore("6");
        score2.setComputerScore("4");
        scoreList.add(score2);
        Score score3 = new Score();
        score3.setName("大猩猩");
        score3.setClasses("三年二班");
        score3.setWriteScore("6");
        score3.setComputerScore("4");
        scoreList.add(score3);
        Score score4 = new Score();
        score4.setName("三井");
        score4.setClasses("三年二班");
        score4.setWriteScore("6");
        score4.setComputerScore("4");
        scoreList.add(score4);
        return scoreList;
    }

    //方法5：java导出多个Excel为zip包
    @RequestMapping("/exportMultipleExcelToZip")
    public void exportMultipleExcelToZip(HttpServletResponse response) throws IOException {
        response.setHeader("Content-disposition", "attachment; filename=" + "test.zip");
        response.setContentType("application/zip; charset=utf-8");

        //创建HSSFWorkbook对象(excel的文档对象)
        XSSFWorkbook wb = null;
        List<Teacher> teacherList = new ArrayList<>();
        //构建sheet页集合
        List<Score> scoreList = new ArrayList<>();
        File templateFile = new File("C:\\Users\\211145187\\Desktop\\data模板.xlsx");

        //.....省略部分代码
        List<Teacher> buildTeacherList = buildTeacherList1();
        List<Score> buildScoreList = buildScoreList1();

        Integer pageLimitSize = exportLimitNum;
        //计算list的分页数量
        Integer pageCount = ExportUtil.getPageCount(buildTeacherList.size(), pageLimitSize);
        List<XSSFWorkbook> excels = new ArrayList<>();
        try {
            for(Integer pageNum = 1; pageNum < pageCount + 1; pageNum++) {
                //注意：每次循环遍历前都需要初始化新的wb对象
                //注意情况1：如果是初始化wb空对象然后手动添加title，下方三行代码不会报错
//                wb = new XSSFWorkbook();
//                buildScoreSheetTitle(wb);
//                buildTeacherSheetTitle(wb);

                //注意情况2：如果是初始化wb对象，并且以流的形式初始化，那么io流必须放在里面才行，如果放在for循环外面会报“Stream Closed”错误
                InputStream io = new FileInputStream(templateFile);
                wb = new XSSFWorkbook(io);
                teacherList = ExportUtil.getPageList(buildTeacherList, pageNum, pageLimitSize, pageCount);
                scoreList = ExportUtil.getPageList(buildScoreList, pageNum, pageLimitSize, pageCount);
                buildScoreSheetParams(wb, scoreList);
                buildTeacherSheetParams(wb, teacherList);
                excels.add(wb);
            }
            //最后统一封装zip压缩包并导出
            ExportUtil.downFileByStream(response, excels);
        } catch (Exception e) {
            logger.error("IOException:", e);
        }
    }

    /**
     * 填充教师页信息
     * @param wb wb
     * @param bodyData bodyData
     */
    private void buildTeacherSheetParams(Workbook wb, List<Teacher> bodyData){
        int teacherColumnCount = wb.getSheetAt(1).getRow(0).getPhysicalNumberOfCells();
        Sheet sheet = wb.getSheetAt(1);
        // build data
        for(int j=0; j<bodyData.size(); j++){
            Teacher itm = bodyData.get(j);
            Row rowData = sheet.createRow(j+1);
            for(int k=0;k<teacherColumnCount; k++){
                Cell cell = rowData.createCell(k);
                cell.setCellValue(getValueByTeacher(k, itm));
            }
        }
    }
    private String getValueByTeacher(int columnIndex,Teacher itm){
        String cellValue;
        switch (columnIndex){
            case 0:cellValue = itm.getName(); break;
            case 1:cellValue = itm.getClasses()+""; break;
            case 2:cellValue = itm.getCollege(); break;
            case 3:cellValue = itm.getAlias(); break;
            default:cellValue=""; break;
        }
        return cellValue;
    }
    /**
     * 填充分数页信息
     * @param wb wb
     * @param bodyData bodyData
     */
    private void buildScoreSheetParams(Workbook wb, List<Score> bodyData){
        int scoreColumnCount = wb.getSheetAt(0).getRow(0).getPhysicalNumberOfCells();
        Sheet sheet = wb.getSheetAt(0);
        // build data
        for(int j=0; j<bodyData.size(); j++){
            Score itm = bodyData.get(j);
            Row rowData = sheet.createRow(j+1);
            for(int k=0;k<scoreColumnCount; k++){
                Cell cell = rowData.createCell(k);
                cell.setCellValue(getValueByScore(k, itm));
            }
        }
    }
    private String getValueByScore(int columnIndex,Score itm){
        String cellValue;
        switch (columnIndex){
            case 0:cellValue = itm.getName(); break;
            case 1:cellValue = itm.getClasses()+""; break;
            case 2:cellValue = itm.getWriteScore(); break;
            case 3:cellValue = itm.getComputerScore(); break;
            default:cellValue=""; break;
        }
        return cellValue;
    }

    /**
     * 构建分数表excel的标头
     * @Author 211145187
     * @Date 2022/2/22 20:20
     * @Param wb wb
     **/
    private void buildScoreSheetTitle(XSSFWorkbook wb) {
        //建立新的sheet对象（excel的表单）
        XSSFSheet sheet=wb.createSheet("成绩表");
        XSSFRow row=sheet.createRow(0);
        //创建单元格并设置单元格内容
        XSSFCell cell0 = row.createCell(0);
        cell0.setCellValue("姓名");
        cell0.setCellStyle(getHeadStyle(wb));
        XSSFCell cell1 = row.createCell(1);
        cell1.setCellValue("班级");
        cell1.setCellStyle(getHeadStyle(wb));
        XSSFCell cell2 = row.createCell(2);
        cell2.setCellValue("笔试成绩");
        cell2.setCellStyle(getHeadStyle(wb));
        XSSFCell cell3 = row.createCell(3);
        cell3.setCellValue("机试成绩");
        cell3.setCellStyle(getHeadStyle(wb));
    }
    /**
     * 构建教师表excel的标头
     * @Author 211145187
     * @Date 2022/2/22 20:20
     * @Param wb wb
     **/
    private void buildTeacherSheetTitle(XSSFWorkbook wb) {
        //建立新的sheet对象（excel的表单）
        XSSFSheet sheet=wb.createSheet("教师表");
        XSSFRow row=sheet.createRow(0);
        //创建单元格并设置单元格内容
        XSSFCell cell0 = row.createCell(0);
        cell0.setCellValue("姓名");
        cell0.setCellStyle(getHeadStyle(wb));
        XSSFCell cell1 = row.createCell(1);
        cell1.setCellValue("班级");
        cell1.setCellStyle(getHeadStyle(wb));
        XSSFCell cell2 = row.createCell(2);
        cell2.setCellValue("所属学院");
        cell2.setCellStyle(getHeadStyle(wb));
        XSSFCell cell3 = row.createCell(3);
        cell3.setCellValue("别名");
        cell3.setCellStyle(getHeadStyle(wb));
    }

    /**
     * 设置样式
     * @Author 211145187
     * @Date 2022/2/22 20:15
     * @Param wb wb
     * @Return CellStyle
     **/
    private CellStyle getHeadStyle(Workbook wb) {
        CellStyle cellStyle = wb.createCellStyle();
        //用于设置前景颜色
        cellStyle.setFillForegroundColor(IndexedColors.SKY_BLUE.getIndex());
        /**
         * setFillPattern用于设置单元格填充样式
         * 注意：
         *      1）setFillPattern必须设置否则光设置setFillForegroundColor无效
         *      2）3.10.1版本支持short类型参数，而3.17版本支持FillPatternType类型参数
         */
        cellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
        return cellStyle;
    }
}

四、可能遇到的问题

错误场景1：java.io.IOException: Stream closed

原因分析：

我这里导致流关闭会有2种场景触发：
场景1：工具类方法downFileByStream()中的for循环执行write()方法。
场景2：wb = new XSSFWorkbook(io);通过IO流初始化wb对象时。

解决方案：

针对场景1中的解决方案就是：Workbook的write()方法最终会关闭它写入的输出流。如果只是一次性全部输出那就不会碰到这种问题，但是现在的场景是工具类方法downFileByStream()中的for循环执行write()方法，所以解决方案就是用一个ByteArrayOutputStream去接收存储当前Workbook的内容，这样哪怕Workbook关闭了，但是内容已经提前存入了ByteArrayOutputStream中，只要读取了就可以继续使用。因此才有这样的如下写法：

/**
     * 直接下载zip包
     * @param response response
     * @param excels wb集合
     */
    public static void downFileByStream(HttpServletResponse response, List<XSSFWorkbook> excels){
        try {
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            ZipOutputStream zipOutputStream = new ZipOutputStream(toClient);
            for(int i=0; i<excels.size(); i++){
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                // 将Workbook写入内存流
                excels.get(i).write(baos);
                ZipEntry zipEntry = new ZipEntry("data" + i + ".xlsx");
                zipOutputStream.putNextEntry(zipEntry);
                // 将内存流写入Zip文件
                zipOutputStream.write(baos.toByteArray());
            }
            zipOutputStream.closeEntry();
            zipOutputStream.flush();
            zipOutputStream.close();
        }catch (Exception e){
            logger.error("downFileByStream==========fail:{}", e.getMessage());
        }
    }

针对场景2中的解决方案就是：把IO流初始化提到for循环里面，如实有了如下写法：

for(Integer pageNum = 1; pageNum < pageCount + 1; pageNum++) {
                //注意：每次循环遍历前都需要初始化新的wb对象
                //注意情况1：如果是初始化wb空对象然后手动添加title，下方三行代码不会报错
//                wb = new XSSFWorkbook();
//                buildScoreSheetTitle(wb);
//                buildTeacherSheetTitle(wb);

                //注意情况2：如果是初始化wb对象，并且以流的形式初始化，那么io流必须放在里面才行，如果放在for循环外面会报“Stream Closed”错误
                InputStream io = new FileInputStream(templateFile);
                wb = new XSSFWorkbook(io);
                ...
            }

错误场景2：调用接口没有另存为弹窗，但是F12查看接口结果返回一堆乱码

错误原因分析：可能是返回结果HttpServletResponse设置的setContentType格式不对。

正确的应该设置为如下，一定要设置为application/zip：

response.setHeader("Content-disposition", "attachment; filename=" + "test.zip");
response.setContentType("application/zip; charset=utf-8");