如何实现下载PDF时弹出下载对话框？

需要两个链接，一个实现PDF在线打开，一个实现PDF下载。
在线打开
请问PDF下载该如何实现？
百度文库里的PDF是可以弹出下载对话框的。

首先给你之前我写的代码 自己改改吧。

重点是 设置contentType为下载 否则如pdf默认是打开的
response.setContentType("application/x-download");
response.setHeader("Content-Disposition", "attachment;filename=\"" + displayFilename + "\"");

[code="java"]package cn.javass.ssonline.upload.web.servlet;

import cn.javass.ssonline.upload.util.UploadUtils;

import java.io.*;
import java.net.URLDecoder;
import java.net.URLEncoder;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends HttpServlet
{
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
doPost(req, resp);
}

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
{
//只允许有一个参数 filename

String filename = new String(req.getQueryString().getBytes("ISO-8859-1"), "UTF-8").substring(9);
if ((filename == null) || (filename.trim().length() == 0) || (filename.contains("\\.\\."))) {
  resp.setContentType("text/html;charset=utf-8");
  resp.getWriter().write("您下载的文件不存在！");
  return;
}
download(req, resp, filename);

}

private void download(HttpServletRequest request, HttpServletResponse response, String filename)
{
String userAgent = request.getHeader("User-Agent");
boolean isIE = (userAgent != null) && (userAgent.toLowerCase().indexOf("msie") != -1);
try
{
filename = URLDecoder.decode(filename, "UTF-8");

  String filePath = UploadUtils.getUploadDir(request) + filename;

  File file = new File(filePath);
  if ((!(file.exists())) || (!(file.canRead()))) {
    response.setContentType("text/html;charset=utf-8");
    response.getWriter().write("您下载的文件不存在！");
    return;
  }
  byte[] buf = new byte[1024];
  int len = 0;
  BufferedInputStream br = null;
  OutputStream ut = null;
  response.reset();

  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "must-revalidate, no-transform");
  response.setDateHeader("Expires", 0L);

  String displayFilename = filename.substring(filename.lastIndexOf("_") + 1);
  displayFilename = displayFilename.replace(" ", "_");
  response.setContentType("application/x-download");

  displayFilename = "[私塾在线学习网]"+displayFilename;
  if (isIE) {
    displayFilename = URLEncoder.encode(displayFilename, "UTF-8");
    response.setHeader("Content-Disposition", "attachment;filename=\"" + displayFilename + "\"");
  } else {
    displayFilename = new String(displayFilename.getBytes("UTF-8"), "ISO8859-1");
    response.setHeader("Content-Disposition", "attachment;filename=" + displayFilename);
  }

  br = new BufferedInputStream(new FileInputStream(file));
  ut = response.getOutputStream();
  while ((len = br.read(buf)) != -1)
    ut.write(buf, 0, len);
}
catch (Exception e) {
  e.printStackTrace();
}

}
}[/code]