文件下载需求：
1. 页面显示超链接
2. 点击超链接后弹出下载提示框
3. 完成图片文件下载
分析：
1. 超链接指向的资源如果能够被浏览器解析，则在浏览器中展示，
如果不能解析，则弹出下载提示框。不满足需求。
2. 任何资源都必须弹出下载提示框。
3. 使用响应头设置资源的打开方式：
*content-disposition：attename；filename=xxx;
步骤
1. 定义页面，编辑超链接href属性，属性值指向Servlet，
传递资源名称filename
2. 定义Servlet
1. 获取文件的名称
2. 使用字节输入流去加载文件进去内存（涉及真实路径）
3. 指定response响应头：
*content-disposition：attename；filename=xxx;
4. 将数据写出到response输出流即可
问题
中文文件名的问题
解决思路：
1. 获取客户端浏览器使用的版本信息
2. 根据不同的版本信息，我们设置filename的编码方式不同
代码
结构
DownloadServlet
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| package com.web.download;
import com.web.utils.DownLoadUtils;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
@WebServlet(urlPatterns = "/downLoad")
public class DownloadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getParameter("filename");
ServletContext servletContext = this.getServletContext();
String realPath = servletContext.getRealPath("/img/"+filename);
FileInputStream fis = new FileInputStream(realPath);
String mimeType = servletContext.getMimeType(filename);
response.setHeader("content-type",mimeType);
String agent = request.getHeader("user-agent");
filename = DownLoadUtils.getFileName(agent, filename);
response.setHeader("content-disposition","attachment;filename="+filename);
ServletOutputStream sos = response.getOutputStream();
byte[] buff = new byte[1024*8];
int len = 0;
while((len=fis.read(buff))!=-1){
sos.write(buff,0,len);
}
fis.close();
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
|
中文编码类
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| package com.web.utils;
import sun.misc.BASE64Encoder;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
public class DownLoadUtils {
public static String getFileName(String agent, String filename) throws UnsupportedEncodingException {
if (agent.contains("MSIE")) {
filename = URLEncoder.encode(filename, "utf-8");
filename = filename.replace("+", " ");
} else if (agent.contains("Firefox")) {
BASE64Encoder base64Encoder = new BASE64Encoder();
filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
filename = URLEncoder.encode(filename, "utf-8");
}
return filename;
}
}
|
下载HTML页面
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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>下载</title>
</head>
<body>
<a href="/3_response_war_exploded/img/1.jpg">图片1</a>
<a href="/3_response_war_exploded/img/2.jpg">图片2</a>
<hr/>
<a href="/3_response_war_exploded/downLoad?filename=1.jpg">图片1</a>
<a href="/3_response_war_exploded/downLoad?filename=九尾.jpg">图片1（中文）</a>
<a href="/3_response_war_exploded/downLoad?filename=2.jpg">图片2</a>
</body>
</html>
|