使用Apache POI創建和下載使用ahref鏈接的excel文件

我有一個JSP頁面上的Excel文件列表，這些文件以表格形式存儲在數據庫中。他們是超鏈接。我需要下載文件，只要用戶點擊一個特定的文件。使用Apache POI創建和下載使用ahref鏈接的excel文件

我對它有以下代碼。

JSP頁面

<html> 
<head> 
    <title></title> 
</head> 
<body> 
<% 
    List<String> encrypted = (List<String>)session.getAttribute("encryptedlist"); 
    List<String> original = (List<String>)session.getAttribute("originallist"); 
    List<String> decrypted = (List<String>)session.getAttribute("decryptedlist"); 

%> 

<table> 
    <tr> 
    <td style="font-weight: bold">Original Files</td> 
    <td style="font-weight: bold">Encrypted Files</td> 
    <td style="font-weight: bold">Decrypted Files</td> 
    </tr> 
    <%for(int i=0;i<size;i++) {%> 
    <tr> 
    <td><a href="DownloadServlet1?file=<%=original.get(i)%>"><%=original.get(i)%></a></td> 
    <td><a href="DownloadServlet1?file=<%=encrypted.get(i)%>"><%=encrypted.get(i)%></a></td> 
    <td><a href="DownloadServlet2?file=<%=decrypted.get(i)%>"><%=decrypted.get(i)%></a></td> 
    </tr> 
    <%}%> 
</table> 
</body> 
</html>

SERVLET

public class DownloadServlet1 extends HttpServlet { 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 

    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 

     String file = request.getParameter("file"); 
     System.out.println(file); 
     int columns = getCount(file); 
     System.out.println(columns); 
     List<String> columnNames = getColumnNames(file,columns); 
     System.out.println(columnNames); 
     saveFile(columnNames,columns,file,response); 
     response.sendRedirect("Login.jsp"); 
    } 

    protected int getCount(String file){ 
     //String sql = "select * from " + "`" + file + "`"; 
     int col=0; 
     try { 
      Connection con = DBOperations.getConnection(); 
      Statement st = con.createStatement(); 
      ResultSet rs = st.executeQuery("SELECT * FROM " + file); 
      System.out.println("SELECT * FROM " + file); 
      ResultSetMetaData md = rs.getMetaData(); 
      col = md.getColumnCount(); 
     }catch (Exception ex) 
     { 
      System.out.println("getcount" + ex); 
     } 
     return col; 
    } 

    protected List<String> getColumnNames(String file, int columns) 
    { 
     List<String> columnNames = new ArrayList<>(); 
     try { 
      Connection con = DBOperations.getConnection(); 
      Statement st = con.createStatement(); 
      String sql = "Select * from " + file; 
      System.out.println("getcolumnnames " + sql); 
      ResultSet rs = st.executeQuery(sql); 
      System.out.println("SELECT * FROM " + file); 
      ResultSetMetaData md = rs.getMetaData(); 
      for (int i = 1; i <= columns; i++){ 
       String col_name = md.getColumnName(i); 
       columnNames.add(col_name); 
       //System.out.println(col_name); 
      } 
     }catch (Exception ex) 
     { 
      System.out.println("get column names"+ex); 
     } 
     return columnNames; 
    } 
    protected void saveFile(List<String> columnNames,int columns,String file,HttpServletResponse response) 
    { 
     Connection con = DBOperations.getConnection(); 

     response.setContentType("application/vnd.ms-excel"); 
     response.setHeader("Content-Disposition", "attachment; filename="+file+".xls"); 
     String excelFileName = file; 

     String sheetName = "Sheet1";//name o sheet 

     XSSFWorkbook wb = new XSSFWorkbook(); 
     XSSFSheet sheet = wb.createSheet(sheetName) ; 

     //iterating r number of rows 
     for (int r=0;r < 1; r++) 
     { 
      XSSFRow row = sheet.createRow(r); 

      //iterating c number of columns 
      for (int c=0;c < columns; c++) 
      { 
       XSSFCell cell = row.createCell(c); 

       cell.setCellValue(columnNames.get(c)); 
      } 
     } 

     try 
     { 
      String sql = "Select * from " + file; 
      System.out.println(sql); 
      Statement st = con.createStatement(); 
      ResultSet rs = st.executeQuery(sql); 
      int r=1; 
      while(rs.next()) 
      { 
       XSSFRow row = sheet.createRow(r); 
       for(int c=1;c<columns;c++) 
       { 
        XSSFCell cell = row.createCell(c); 

        cell.setCellValue(rs.getString(c)); 
       } 
       r=r+1; 
      } 

     }catch (Exception ex) 
     { 
      System.out.println(ex); 
     } 

     try { 
      FileOutputStream fileOut = new FileOutputStream(excelFileName); 
      //write this workbook to an Outputstream. 
      wb.write(fileOut); 
      fileOut.flush(); 
      fileOut.close(); 
     }catch (Exception ex) 
     { 
      System.out.println(ex); 
     } 

    } 
}

利用getCount函數返回的列數從數據庫的文件。 getColumnNames獲取所有列的名稱。

這兩個函數返回正確的值，這表明在訪問數據庫表

的saveFile的功能應該下載Excel文件沒有問題。

我得到這個錯誤在瀏覽器上的網頁

The webpage at http://localhost:8084/DownloadServlet1?file=Hil_1566869_27_08_17_20_24_18 might be temporarily down or it may have moved permanently to a new web address.

可能是什麼問題呢？

來源

2017-08-27 user3508140

直接寫入Excel文檔到HTTP響應：

wb.write(response.getOutputStream());

有一個在本地保存在服務器上的Excel文件沒有意義的。

另外，不要重定向到Login.jsp，這可能是導致錯誤的原因。

來源

2017-08-27 21:12:16 r0the

我在刪除Login.jsp和wb.write（response.getOutpurStream（））後得到相同的錯誤; – user3508140

使用Apache POI創建和下載使用ahref鏈接的excel文件

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