java 通用檔案下載 excel,pdf,word,jpg

<%@ page contentType="text/html; charset=GBK" %>
  <%@ page autoFlush="false" %>
  <%@ page import="java.sql.*" %>
  <%@ page import="java.io.*" %>
  <%@ page import="java.util.*" %>
  <%@ page import="java.awt.*" %>
  <%@ page import="java.awt.image.*" %>
  <%@ page import="com.sun.image.codec.jpeg.*" %>
  <%@ page import="com.sun.image.codec.jpeg.*" %>
  <%!
    public static String getcontentType(String pextFileName)  //獲得副檔名，by gisoracle

   {
      String pext=pextFileName.toLowerCase();
      if (pext.equals(".xls"))
      {
        return "application/vnd.ms-excel";
      }
      if (pext.equals(".doc"))
      {
        return "application/msword";
      }
      if (pext.equals(".txt"))
      {
        return "text/plain";
      }
      if (pext.equals(".pdf"))
      {
        return "application/pdf";
      }
      if (pext.equals(".jpg")||pext.equals(".jpeg"))
      {
        return "image/jpeg";
      }
      if (pext.equals(".ppt"))
      {
        return "application/vnd.ms-powerpoint";
      }
      if (pext.equals(".gif"))
      {
        return "image/gif";
      }
      return "text/html";
    }
%>
<%
  String filename =request.getParameter("filename");
  File downFile = new File(filename);
  String fileext=FileOper.getFiletype(downFile);
  System.out.println("fileext="+fileext);
  String contentType1 =getcontentType(fileext);
  System.out.println("contentType1="+contentType1);
  try {
  out.clear();
  response.setContentType(contentType1);
  filename = new String(filename.getBytes("GBK"), "ISO-8859-1");
  response.setHeader("Content-Disposition","attachment; filename=" +downFile.getName());
  response.addHeader("Cache-Control", "no-cache");
  InputStream blobStream = new FileInputStream(downFile);
  ServletOutputStream outStream = response.getOutputStream();
  byte[] buffer = new byte[10 * 1024];
  int nbytes = 0;
  while ( (nbytes = blobStream.read(buffer)) != -1) {
  outStream.write(buffer, 0, nbytes);
  }
  outStream.flush();
  outStream.close();
  blobStream.close();
  }
  catch (Exception e) {
  System.out.println(e);
  }
%>

調用方法:location.href="downfile.jsp?filename="+str;