http上载小实例 _Web前端

http下载小实例
前端download.jsp

 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>   
 <%  
 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">  
   
   </head>  
     <%=path %>
   <body>
     <p><a href=DownFileServlet?filename=java.rar>java</a></p>
     <p><a href=DownFileServlet?filename=dos.rar>dos</a></p> 
     <p><a href=DownFileServlet?filename=com.rar>com</a></p>
   </body>  
 </html>

后台servlet:


package com.guohui.test.file;

import java.io.BufferedInputStream;
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;

/**
 * Servlet implementation class DownFileServlet
 */
public class DownFileServlet extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 7627015152811667298L;
	private static final String CONTENT_TYPE = "text/html; charset=utf-8";

	// 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
		//String fileDir = System.getProperty("user.dir",".")+"/dos.rar";// + File.separator + filename;
		//File file = new File(fileDir);
		
		InputStream is=getServletContext().getResourceAsStream( "resource"+File.pathSeparator+filename );
		
		String fileDir2 = this.getServletContext().getRealPath("resource");
		
		File file = new File(fileDir2+"/"+filename);
		System.out.println(fileDir2+"/"+filename);
		
		System.out.println(File.separator);
		//File.pathSeparator// :
		//File.separator // /
		

		// 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() {
	}
}