使用servlet导出和下载excel文件

Question

我正在使用GWT应用程序。当我单击按钮时，我将请求参数传递给数据库并获取结果。使用此结果集我想创建excel并且必须为用户提供下载弹出窗口。 Excel文件正在创建但不是弹出窗口 代码如下：

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import com.excelexporter.shared.ResponseObj;

public class ExportExcel extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static ObjectInputStream inObj;;
    private String encoding = "ISO-8859-1";
    List<ResponseObj> implRes = new ArrayList<ResponseObj>();

    @SuppressWarnings("unchecked")
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        inObj = new ObjectInputStream(req.getInputStream());

        try {
            HSSFWorkbook workbook = new HSSFWorkbook(); 

            //Create a blank sheet
            HSSFSheet sheet = workbook.createSheet("Employee Data");
            implRes = (List<ResponseObj>)inObj.readObject();
            Map<Integer, Object[]> data = new TreeMap<Integer, Object[]>();
            data.put(1, new Object[] {"ID", "Mark_1", "Mark_2", "Mark_3","Mark_4", "Mark_5"});

            String html = "html";
            String fileName = "Export.xls";
            if (!fileName.endsWith(".xls")) {
                fileName = fileName + ".xls";
            }
            resp.setContentType("application/vnd.ms-excel");// magic is here
            resp.setHeader("Content-Disposition", "attachment; filename=test.xls");

            if(implRes!=null){
                for(int i=0;i<implRes.size();i++){
                    data.put(i+2, new Object[] {i+1, implRes.get(i).getMark_1(),
                        implRes.get(i).getMark_1(),
                        implRes.get(i).getMark_1(),
                        implRes.get(i).getMark_1(),
                        implRes.get(i).getMark_1()});
                }
            }

            Set<Integer> keyset = data.keySet();
            int rownum = 0;
            for (int key : keyset)
            {
                Row row = sheet.createRow(rownum++);
                Object [] objArr = data.get(key);
                int cellnum = 0;
                for (Object obj : objArr)
                {
                   Cell cell = row.createCell(cellnum++);
                   if(obj instanceof String)
                        cell.setCellValue((String)obj);
                    else if(obj instanceof Integer)
                        cell.setCellValue((Integer)obj);
                }
            }

             //FileOutputStream out = new FileOutputStream(new File("howtodoinjava_demo.xlsx"));
            OutputStream out = resp.getOutputStream();
            workbook.write(out);    
                out.close();
             workbook.close();
                System.out.println("howtodoinjava_demo.xlsx written successfully on disk.");

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


    }
}

我正在使用以下代码调用上面的servlet：

public List<ResponseObj> greetServer(Requester myReq) throws IllegalArgumentException {

        if(myReq.getUserName().equalsIgnoreCase("Admin")){
            for(int i =1;i<=100;i++){
                myRes = new ResponseObj();
                myRes.setMark_1(new Integer(10*i).toString());
                myRes.setMark_2(new Integer(30*i).toString());
                myRes.setMark_3(new Integer(50*i).toString());
                myRes.setMark_4(new Integer(70*i).toString());
                myRes.setMark_5(new Integer(90*i).toString());
                res.add(myRes);
            }

        }
        try {
             url = new URL("http://127.0.0.1:8888/excelexporter/excel?a=res");
            con = (HttpURLConnection)url.openConnection();
            con.setRequestMethod("POST");
            con.setDoInput(true);
            con.setDoOutput(true);
            con.setUseCaches(false);
            con.setDefaultUseCaches(false);
            con.setRequestProperty("Content-Type", "application/octet-stream");
            objOut = new ObjectOutputStream(con.getOutputStream());
            objOut.writeObject(res);
            objIn = new ObjectInputStream(con.getInputStream());
            String status = (String)objIn.readObject();
            System.out.println("Hello Status   " +status);          
            objIn.close();
            objOut.flush();
            objOut.close();


        } catch (Exception e) {
            GWT.log("Warn#####");
        } 

        return res;
    }