实现文件下载的java代码

//这是实现下载类(servlet)，详细思路代码例如以下：

//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());

//设置附加文件名称

// 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();

//開始循环下载

while(k

int j=buff.read(b,0,1024);

k+=j;

//将b中的数据写到client的内存

myout.write(b,0,j);

}

//将写入到client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，假设没有连接数据库，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页面加载写发，也可连接数据库(案例代码也在)

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

My JSP 'book.jsp' starting page

//Vector vv=(Vector)session.getAttribute("message");

//for(int i=0;i

// MessagesBean mb=(MessagesBean)vv.get(i);

// out.println("

");

// out.println("

"+mb.getSender()+"");

// out.println("

"+mb.getMess_time()+"");

// out.println("

"+mb.getGeter()+"");

// out.println("

"+mb.getMess_content()+"");

String filename=null;

session.setAttribute("java.rar",filename);

//取得文件名称

// filename=getFilepath().substring(mb.getFilepath().lastIndexOf("/")+1);

out.println("

5.1下载书--java");//java.rar这个能够改成变量

out.println("

dos视频教程");

out.println("

经常使用DOS命令");

out.println("

");

// }

%>

//这是web.xml配置文件，这非常重要，不然，非常难实现哦

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">

This is the description of my J2EE component

This is the display name of my J2EE component

FileDownServlet

com.message.FileDownServlet

FileDownServlet

/FileDownServlet