Java文件下载的几种方式

public HttpServletResponse download(String path, HttpServletResponse response) {try {// path是指欲下载的文件的路径。File file = new File(path);// 取得文件名。String filename = file.getName();// 取得文件的后缀名。String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();// 以流的形式下载文件。InputStream fis = new BufferedInputStream(new FileInputStream(path));byte[] buffer = new byte[fis.available()];fis.read(buffer);fis.close();// 清空responseresponse.reset();// 设置response的Headerresponse.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));response.addHeader("Content-Length", "" + file.length());OutputStream toClient = new BufferedOutputStream(response.getOutputStream());response.setContentType("application/octet-stream");toClient.write(buffer);toClient.flush();toClient.close();} catch (IOException ex) {ex.printStackTrace();}return response;}public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {// 下载本地文件String fileName = "Operator.doc".toString(); // 文件的默认保存名// 读到流中InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径// 设置输出的格式response.reset();response.setContentType("bin");response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");// 循环取出流中的数据byte[] b = new byte[100];int len;try {while ((len = inStream.read(b)) > 0)response.getOutputStream().write(b, 0, len);inStream.close();} catch (IOException e) {e.printStackTrace();}}public void downloadNet(HttpServletResponse response) throws MalformedURLException {// 下载网络文件int bytesum = 0;int byteread = 0;URL url = new URL("windine.blogdriver.com/logo.gif");try {URLConnection conn = url.openConnection();InputStream inStream = conn.getInputStream();FileOutputStream fs = new FileOutputStream("c:/abc.gif");byte[] buffer = new byte[1204];int length;while ((byteread = inStream.read(buffer)) != -1) {bytesum += byteread;System.out.println(bytesum);fs.write(buffer, 0, byteread);}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}  //支持在线打开文件的一种方式public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception {File f = new File(filePath);if (!f.exists()) {response.sendError(404, "File not found!");return;}BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));byte[] buf = new byte[1024];int len = 0;response.reset(); // 非常重要if (isOnLine) { // 在线打开方式URL u = new URL("file:///" + filePath);response.setContentType(u.openConnection().getContentType());response.setHeader("Content-Disposition", "inline; filename=" + f.getName());// 文件名应该编码成UTF-8} else { // 纯下载方式response.setContentType("application/x-msdownload");response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());}OutputStream out = response.getOutputStream();while ((len = br.read(buf)) > 0)out.write(buf, 0, len);br.close();out.close();}

Java的servlet实现文件下载
实现文件下载的java代码

//这是实现下载类（servlet），具体思路代码如下：//也可连接数据库package com.message;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;public class FileDownServlet extends HttpServlet {    private static final String CONTENT_TYPE = "text/html; charset=GBK";    //Initialize global variables    public void init() throws ServletException {    }    //Process the HTTP Get request    public void doGet(HttpServletRequest request, HttpServletResponse response) throws            ServletException, IOException {        response.setContentType(CONTENT_TYPE);        //得到下载文件的名字        //String filename=request.getParameter("filename");                //解决中文乱码问题        String filename=new String(request.getParameter("filename").getBytes("iso-8859-1"),"gbk");        //创建file对象        File file=new File("F://book//WebRoot//"+filename);        //设置response的编码方式        response.setContentType("application/x-msdownload");        //写明要下载的文件的大小        response.setContentLength((int)file.length());        //设置附加文件名       // response.setHeader("Content-Disposition","attachment;filename="+filename);                //解决中文乱码    response.setHeader("Content-Disposition","attachment;filename="+new String(filename.getBytes("gbk"),"iso-8859-1"));               //读出文件到i/o流        FileInputStream fis=new FileInputStream(file);        BufferedInputStream buff=new BufferedInputStream(fis);        byte [] b=new byte[1024];//相当于我们的缓存        long k=0;//该值用于计算当前实际下载了多少字节        //从response对象中得到输出流,准备下载        OutputStream myout=response.getOutputStream();        //开始循环下载        while(k<file.length()){            int j=buff.read(b,0,1024);            k+=j;            //将b中的数据写到客户端的内存            myout.write(b,0,j);        }        //将写入到客户端的内存的数据,刷新到磁盘        myout.flush();    }    //Process the HTTP Post request    public void doPost(HttpServletRequest request, HttpServletResponse response) throws            ServletException, IOException {        doGet(request, response);    }    //Clean up resources    public void destroy() {    }}

//这是javabean写法 ，主要是实现和数据库连接的，如果没有连接数据库，就可直接不要这package com;public class MessageBean { private String Message; public String getMessage() {  return Message; } public void setMessage(String message) {  Message = message; }}

//HTML页面载入写发，也可连接数据库（案例代码也在）<%@ page language="java" import="java.util.*,com.message.*" pageEncoding="gbk"%><jsp:directive.page import="com.MessageBean;"/><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>My JSP 'book.jsp' starting page</title>     <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0">     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> -->  </head>    <body>    <!--  <a href="java.rar">5.1下载书--java</a> <br>-->    <%  //Vector vv=(Vector)session.getAttribute("message");  //for(int i=0;i<vv.size();i++){   // MessagesBean mb=(MessagesBean)vv.get(i);   // out.println("<tr>");   // out.println("<td>"+mb.getSender()+"</td>");   // out.println("<td>"+mb.getMess_time()+"</td>");   // out.println("<td>"+mb.getGeter()+"</td>");   // out.println("<td>"+mb.getMess_content()+"</td>");String filename=null;session.setAttribute("java.rar",filename);    //取得文件名   // filename=getFilepath().substring(mb.getFilepath().lastIndexOf("/")+1);    out.println("<td><a href=FileDownServlet?filename=java.rar>5.1下载书--java</a></td>");//java.rar这个可以改成变量    out.println("<td><a href=FileDownServlet?filename=dos.rar>dos视频教程</a></td>");    out.println("<td><a href=FileDownServlet?filename=常用DOS命令.rar>常用DOS命令</a></td>");    out.println("</tr>"); // }  %>  </body></html>

//这是web.xml配置文件，这很重要，不然，很难实现哦<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4"  xmlns="http://java.sun.com/xml/ns/j2ee"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee  http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>FileDownServlet</servlet-name>    <servlet-class>com.message.FileDownServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>FileDownServlet</servlet-name>    <url-pattern>/FileDownServlet</url-pattern>  </servlet-mapping></web-app>