1 代码实现
1 index.jsp代码
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>文件下载演示</title>
</head>
<body>
<h1>使用a标签直接指向服务器上的资源</h1>
<a href="${pageContext.request.contextPath }/download/a.flv">a.flv</a><br/>
<a href="${pageContext.request.contextPath }/download/a.jpg">a.jpg</a><br/>
<a href="${pageContext.request.contextPath }/download/a.mp3">a.mp3</a><br/>
<a href="${pageContext.request.contextPath }/download/a.mp4">a.mp4</a><br/>
<a href="${pageContext.request.contextPath }/download/a.txt">a.txt</a><br/>
<a href="${pageContext.request.contextPath }/download/a.zip">a.zip</a>
<h1>使用服务器端编码的方式实现文件下载</h1>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.flv">a.flv</a><br/>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.jpg">a.jpg</a><br/>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.mp3">a.mp3</a><br/>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.mp4">a.mp4</a><br/>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.txt">a.txt</a><br/>
<a href="${pageContext.request.contextPath }/downloadServlet?filename=a.zip">a.zip</a>
</body>
</html>
2 downloadServlet入门代码
package www.test.web.servlet;
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 {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1 获取要下载的文件的名称
String filename = request.getParameter("filename"); //a.jpg
// 2 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));
// 3 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);
// 4 获取文件的绝对路径
String realPath = this.getServletContext().getRealPath("download/"+filename);
// 5 获得该文件的输入流
InputStream in = new FileInputStream(realPath);
// 6 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();
// 7 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);
}
// 8 关闭资源
in.close();
//out.close(); //respone 获得的流可以不用手动关闭, 会自动关闭。
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
3 downloadServlet2详细代码
package www.test.web.servlet;
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 {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1 获取要下载的文件的名称
String filename = request.getParameter("filename"); // 这里获取到的中文是乱码
// ???.jpg
// 解决获取到的中文名乱码问题
filename = new String(filename.getBytes("ISO8859-1"), "UTF-8");
// 2 获得请求头中的 User-Agent
String agent = request.getHeader("User-Agent");
// 3 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");
}
// 4 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));
// 5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);
// 6 获取文件的绝对路径
String realPath = this.getServletContext().getRealPath("download/"+filename);
// 7用一个输入流和文件相关联
InputStream in = new FileInputStream(realPath);
// 8 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();
// 9 文件拷贝的模板代码
int len =0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))!=-1){
out.write(buffer, 0, len);
}
//10 关闭资源
in.close();
//out.close();//respone 获得的流可以不用手动关闭,会自动关闭。但是自己 new 的流一定要关闭
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}