基于Servlet的基本下载代码示例

package com.itheima.content;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

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

public class DownloadServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//获得要下载的文件的名称
		String filename = request.getParameter("filename");//a.flv

		//要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
		response.setContentType(this.getServletContext().getMimeType(filename));
		//告诉客户端该文件不是直接解析 而是以附件形式打开(下载)
		response.setHeader("Content-Disposition", "attachment;filename="+filename);

		//获取文件的绝对路径
		String path = this.getServletContext().getRealPath("download/"+filename);
		//获得该文件的输入流
		InputStream in = new FileInputStream(path);
		//获得输出流---通过response获得的输出流 用于向客户端写内容
		ServletOutputStream out = response.getOutputStream();
		//文件拷贝的模板代码
		int len = 0;
		byte[] buffer = new byte[1024];
		while((len=in.read(buffer))>0){
			out.write(buffer, 0, len);
		}

		in.close();
		//out.close();

	}

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

增强

package com.itheima.content;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;

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

import sun.misc.BASE64Encoder;

public class DownLoadServlet2 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//*******文件名称是中文的下载*******


		//获得要下载的文件的名称
		String filename = request.getParameter("filename");//????.jpg
		//解决获得中文参数的乱码----下节课讲
		filename = new String(filename.getBytes("ISO8859-1"),"UTF-8");//美女.jpg

		
		//获得请求头中的User-Agent
		String agent = request.getHeader("User-Agent");
		//根据不同浏览器进行不同的编码
		String filenameEncoder = "";
		if (agent.contains("MSIE")) {
			// IE浏览器
			filenameEncoder = URLEncoder.encode(filename, "utf-8");
			filenameEncoder = filenameEncoder.replace("+", " ");
		} else if (agent.contains("Firefox")) {
			// 火狐浏览器
			BASE64Encoder base64Encoder = new BASE64Encoder();
			filenameEncoder = "=?utf-8?B?"
					+ base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
		} else {
			// 其它浏览器
			filenameEncoder = URLEncoder.encode(filename, "utf-8");				
		}



		//要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
		response.setContentType(this.getServletContext().getMimeType(filename));
		//告诉客户端该文件不是直接解析 而是以附件形式打开(下载)----filename="+filename 客户端默认对名字进行解码
		response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);

		//获取文件的绝对路径
		String path = this.getServletContext().getRealPath("download/"+filename);
		//获得该文件的输入流
		InputStream in = new FileInputStream(path);
		//获得输出流---通过response获得的输出流 用于向客户端写内容
		ServletOutputStream out = response.getOutputStream();
		//文件拷贝的模板代码
		int len = 0;
		byte[] buffer = new byte[1024];
		while((len=in.read(buffer))>0){
			out.write(buffer, 0, len);
		}

		in.close();
		//out.close();

	}

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