JAVA实现在数据库导出到EXCEL并下载

package basedao;

import jxl.*;
import jxl.write.*;
import java.io.*;
import java.util.Iterator;
import java.util.Collection;
import vo.studentVo;
import database.GeneralDAO;
import database.Database;

/**
 * <p>导出学生的用户名和密码到EXCEL表: </p>
 *
 * <p>使用JXL包,实现对EXCEL文件的导出: </p>
 *
 * <p>Copyright: Copyright (c) 2008</p>
 *
 * <p>e21: </p>
 *
 * @author 胡保林
 * @version 1.0
 */
public class importtoExcelDao {
    private String zkStuTable = "xs_2008";
    Database db = new Database("");
    private GeneralDAO dao = null;
    public importtoExcelDao() {
        dao = new GeneralDAO(db, zkStuTable);
    }

    public Collection getStudents(String xxcode) { //取学校的学生姓名，用户名，密码;
        Collection col = null;
        try {
            col = dao.findDatas("XH,XM,MM", "xx=" + xxcode, null, studentVo.class);
            return col;
        } catch (Exception ex) {

        }
        return col;
    }

    public void importUserPwd(String filename, Iterator it) { //filename是生成文件的路径及用户名;it是内容, Iterator it;
        try {
            //open file.
            WritableWorkbook book = Workbook.createWorkbook(new File(filename));
            WritableSheet sheet = book.createSheet("学生用户名及密码表", 0);
            Label label = new Label(0, 0, "姓名");
            sheet.addCell(label);
            label = new Label(1, 0, "用户名");
            sheet.addCell(label);
            label = new Label(2, 0, "密码");
            sheet.addCell(label);
            int row = 1;
            for (; it.hasNext(); ) {
                studentVo vo = (studentVo) it.next();
                Label xm = new Label(0, row, vo.getXm());
                sheet.addCell(xm);
                Label username = new Label(1, row, vo.getXh());
                sheet.addCell(username);
                Label pwd = new Label(2, row, vo.getMm());
                sheet.addCell(pwd);
                // LabelCell label=new jxl.write.Label(0,row,vo.getXm());
                // jxl.write.Number number = new jxl.write.Number(0, row,xm);
                //add defined cell above to sheet instance.
                // sheet.addCell(number);
                //add defined all cell above to case.
                row++;
            }
            book.write();
            book.close();

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

    }

}

package action.importdb;

import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionForm;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.Action;
import basedao.importtoExcelDao;
import java.util.Collection;
import java.util.Iterator;
import java.io.IOException;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import util.*;
import java.io.InputStream;

public class importUserPwdAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request,
                                 HttpServletResponse response) throws
            IOException {
        importtoExcelDao dao = new importtoExcelDao();
        String schoolcode = "420902026006"; //学校代码;
        Collection col = dao.getStudents(schoolcode); //取学校的学生;
        if (col != null) {
            System.out.println("col is " + col.size());
            Iterator it = col.iterator();
            //dao.importUserPwd("d:/Test.xls",it);
            String filename = schoolcode + ".xls"; //学校代码命名的excel表;
            config con = new config();
            String filepath = servlet.getServletContext().getRealPath("/") +
                              con.downloadPath + filename; //生成excel文件的路径;
            dao.importUserPwd(filepath, it);
            InputStream inStream = new FileInputStream(filepath);
            response.reset();
            response.setContentType("bin");
            response.addHeader("Content-Disposition",
                               "attachment;   filename=\"" + filename + "\"");
            byte[] b = new byte[100];
            int len;
            while ((len = inStream.read(b)) > 0) {
                response.getOutputStream().write(b, 0, len);
            }
            inStream.close();
        }
        return null;
    }
}