用jsp+struts2框架代码实现以下功能:导出千万级数据量，要求每50000笔数据导入到excel表格直到导完为止，再讲得到的多个excel表格压缩成zip包，最后导出为一个压缩包

以下是jsp+struts2框架代码实现的示例：

1. 创建一个DownloadAction类，用于处理下载请求：

public class DownloadAction extends ActionSupport {
    private static final long serialVersionUID = 1L;
    
    private String fileName;
    private String contentType;
    private InputStream inputStream;
    private int bufferSize = 1024;
    
    public String execute() throws Exception {
        // 获取数据列表
        List<Data> dataList = getDataList();
        
        // 按照50000笔数据分批导出到excel表格
        int batchCount = (dataList.size() + 49999) / 50000;
        for (int i = 0; i < batchCount; i++) {
            int start = i * 50000;
            int end = Math.min(start + 50000, dataList.size());
            List<Data> batchList = dataList.subList(start, end);
            
            // 生成excel表格并写入数据
            Workbook workbook = createWorkbook(batchList);
            
            // 把excel表格写入输出流
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            workbook.write(baos);
            baos.flush();
            baos.close();
            ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
            
            // 把输出流赋值给inputStream
            inputStream = bais;
            
            // 设置文件名和Content-Type
            fileName = "data_" + (i+1) + ".xls";
            contentType = "application/vnd.ms-excel";
            
            // 返回下载结果
            if (i == batchCount - 1) {
                return "zip";
            } else {
                return "excel";
            }
        }
        
        return null;
    }
    
    // 获取数据列表
    private List<Data> getDataList() {
        // TODO: 获取数据列表的代码
        return null;
    }
    
    // 生成excel表格
    private Workbook createWorkbook(List<Data> dataList) {
        // TODO: 生成excel表格的代码
        return null;
    }

    // Getters and Setters
}

2. 创建一个excel.jsp页面，用于导出单个excel表格：

<%@ page contentType="text/html;charset=UTF-8" %>

<%@ taglib prefix="s" uri="/struts-tags" %>

<s:actionerror />
<s:actionmessage />

<s:form action="download">
    <s:submit value="导出到Excel" />
</s:form>

<%-- 定义下载链接 --%>
<a href="<s:url action='download'/>" target="_blank">下载Excel文件</a>

3. 创建一个zip.jsp页面，用于导出多个excel表格的压缩包：

<%@ page contentType="text/html;charset=UTF-8" %>

<%@ taglib prefix="s" uri="/struts-tags" %>

<s:actionerror />
<s:actionmessage />

<s:form action="download">
    <s:submit value="导出到Excel" />
</s:form>

<%-- 定义下载链接 --%>
<a href="<s:url action='download'/>" target="_blank">下载Zip文件</a>

4. 在struts.xml文件中配置DownloadAction类和对应的结果：

<struts>
    <package name="default" extends="struts-default">
        <action name="download" class="com.example.DownloadAction">
            <result name="excel" type="stream">
                <param name="contentType">${contentType}</param>
                <param name="inputName">inputStream</param>
                <param name="bufferSize">${bufferSize}</param>
                <param name="contentDisposition">attachment;filename="${fileName}"</param>
            </result>
            <result name="zip" type="stream">
                <param name="contentType">application/zip</param>
                <param name="inputName">inputStream</param>
                <<param name="bufferSize">${bufferSize}</param>
                <param name="contentDisposition">attachment;filename="data.zip"</param>
            </result>
        </action>
    </package>
</struts>

5. 编写一个压缩文件的工具类：

public class ZipUtils {
    public static void zipFiles(List<File> fileList, String zipFilePath) throws IOException {
        // 创建ZipOutputStream对象
        ZipOutputStream zipOutputStream = new ZipOutputStream(new FileOutputStream(zipFilePath));
        
        // 遍历文件列表并添加到zip文件中
        for (File file : fileList) {
            // 创建ZipEntry对象
            ZipEntry zipEntry = new ZipEntry(file.getName());
            zipOutputStream.putNextEntry(zipEntry);
            
            // 读取文件并写入ZipOutputStream
            FileInputStream fileInputStream = new FileInputStream(file);
            byte[] buffer = new byte[1024];
            int length = 0;
            while ((length = fileInputStream.read(buffer)) > 0) {
                zipOutputStream.write(buffer, 0, length);
            }
            
            // 关闭ZipEntry和FileInputStream
            zipOutputStream.closeEntry();
            fileInputStream.close();
        }
        
        // 关闭ZipOutputStream
        zipOutputStream.close();
    }
}

6. 在DownloadAction类中调用ZipUtils类生成压缩包：

public class DownloadAction extends ActionSupport {
    private static final long serialVersionUID = 1L;
    
    private String fileName;
    private String contentType;
    private InputStream inputStream;
    private int bufferSize = 1024;
    
    public String execute() throws Exception {
        // 获取数据列表
        List<Data> dataList = getDataList();
        
        // 按照50000笔数据分批导出到excel表格
        List<File> fileList = new ArrayList<>();
        int batchCount = (dataList.size() + 49999) / 50000;
        for (int i = 0; i < batchCount; i++) {
            int start = i * 50000;
            int end = Math.min(start + 50000, dataList.size());
            List<Data> batchList = dataList.subList(start, end);
            
            // 生成excel表格并写入数据
            Workbook workbook = createWorkbook(batchList);
            
            // 把excel表格写入文件
            File file = new File("data_" + (i+1) + ".xls");
            FileOutputStream fileOutputStream = new FileOutputStream(file);
            workbook.write(fileOutputStream);
            fileOutputStream.flush();
            fileOutputStream.close();
            
            // 把文件添加到文件列表中
            fileList.add(file);
        }
        
        // 生成压缩包并赋值给inputStream
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ZipUtils.zipFiles(fileList, baos);
        baos.flush();
        baos.close();
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        inputStream = bais;
        
        // 设置文件名和Content-Type
        fileName = "data.zip";
        contentType = "application/zip";
        
        // 返回下载结果
        return "zip";
    }
    
    // 获取数据列表
    private List<Data> getDataList() {
        // TODO: 获取数据列表的代码
        return null;
    }
    
    // 生成excel表格
    private Workbook createWorkbook(List<Data> dataList) {
        // TODO: 生成excel表格的代码
        return null;
    }

    // Getters and Setters
}

这样就完成了导出千万级数据量、分批导入到excel表格、压缩多个excel表格为zip包、最后导出为一个压缩包的功能。