jsp文件下载功能实现代码

本文实例为大家分享了jsp实现文件下载功能的3种方法，供大家参考，具体内容如下

第一种、采用转发的方式：

package cn.jbit.download.servlet; 

import java.io.IOException; 

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 

public class DownloadServlet extends HttpServlet { 

  private static final long serialVersionUID = 6765085208899952414L; 

  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  } 

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    String filedownload = "/upload/1/10213.jpg";//即将下载的文件的相对路径
    String filedisplay = "10213.jpg";//下载文件时显示的文件保存名称
    response.setContentType("application/x-download");//设置为下载application/x-download
    //response.setContentType("application/x-msdownload");//设置为下载application/x-msdownload
    //response.setContentType("application/octet-stream");//设置为下载application/octet-stream
    response.addHeader("Content-Disposition", "attachment;filename="
        + filedisplay); 

    try {
      RequestDispatcher rd = request.getRequestDispatcher(filedownload);
      if(rd != null)
      {
        rd.forward(request,response);
      }
      response.flushBuffer();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

二、通过输出流的方式：

package cn.jbit.download.servlet; 

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream; 

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 

public class DownloadOfIOServlet extends HttpServlet {
 public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  } 

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    String basePath = request.getSession().getServletContext().getRealPath("/upload"); 

    String filedisplay = "helloworld.jpg";
    String filedownload = basePath + File.separator + "helloworld.jpg";
    response.setContentType("applicaiton/x-download");
    response.addHeader("Content-Disposition", "attachment;filename="+filedisplay); 

    InputStream is = null;
    OutputStream os = null;
    BufferedInputStream bis = null;
    BufferedOutputStream bos = null; 

    is = new FileInputStream(new File(filedownload));
    bis = new BufferedInputStream(is);
    os = response.getOutputStream();
    bos = new BufferedOutputStream(os); 

    byte[] b = new byte[1024];
    int len = 0;
    while((len = bis.read(b)) != -1){
      bos.write(b,0,len);
    } 

    bis.close();
    is.close();
    bos.close();
    os.close();
  }
}

第三种、通过超链接的方式(注意不推荐，因为会暴露下载文件的位置)

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。