IDEA激活码
文件下载案例
需求：
1.页面显示超链接
2.点解超链接后弹出下载提示框
3.完成图片下载
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，如果不能够解析就会弹出下载提示框，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：attachment;filename=xxx
步骤：
1.定义页面，编辑超链接href属性，指向servlet，传递资源名称filename
2.定义Servlet
1.获取文件名称
2.使用字节输入流加载文件进内存
3.指定response响应头：content-disposition：attachment;filename=xxx
4.将数据写到response输出流
<html>
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/18-Http-Response/img/c.jpg">图片1</a>
<a href="/18-Http-Response/img/1.mp3">音乐</a>
<a href="/18-Http-Response/img/2.avi">视频</a>
<a href="/18-Http-Response/DownLoadServlet?filename=c.jpg">图片1</a>
<a href="/18-Http-Response/DownLoadServlet?filename=2.avi">视频</a>
<a href="/18-Http-Response/DownLoadServlet?filename=1.mp3">音乐</a>
</body>
</html>
package download;
import javax.servlet.Servlet;
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("/DownLoadServlet")
public class DownLoadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取请求参数，文件民称
String filename = request.getParameter("filename");
//使用字节输入流加载文件进内存
//找到文件的真实路径
ServletContext context = this.getServletContext();
String realPath = context.getRealPath("/img/"+filename);
//用字节流关联
FileInputStream fis = new FileInputStream(realPath);
//设置response的响应头
//设置响应头的类型
String mimeType = context.getMimeType(filename);
response.setHeader("content-type",mimeType);
//设置响应头的打开方式
response.setHeader("content-disposition","attachment;filename"+filename);
//将输入流的数据写出到输出流中
ServletOutputStream sos = response.getOutputStream();
byte[] buff = new byte[1024];
int len = 0;
while((len=fis.read(buff))!=-1){
sos.write(buff,0,len);
}
fis.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
中文文件名称问题
因为IE浏览器的版本较低，当文件名为中文时直接报了异常
高级的火狐浏览器下：
解决思路：
1.获取客户端使用的浏览器版本信息
2.根据不同的版本信息，设置filename的编码方式不同
package util;
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")) {
// IE浏览器
filename = URLEncoder.encode(filename, "utf-8");
filename = filename.replace("+", " ");
} else if (agent.contains("Firefox")) {
// 火狐浏览器
BASE64Encoder base64Encoder = new BASE64Encoder();
filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
// 其它浏览器
filename = URLEncoder.encode(filename, "utf-8");
}
return filename;
}
}
package download;
import util.DownLoadUtils;
import javax.servlet.Servlet;
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("/DownLoadServlet")
public class DownLoadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取请求参数，文件民称
String filename = request.getParameter("filename");
//使用字节输入流加载文件进内存
//找到文件的真实路径
ServletContext context = this.getServletContext();
String realPath = context.getRealPath("/img/"+filename);
//用字节流关联
FileInputStream fis = new FileInputStream(realPath);
//设置response的响应头
//设置响应头的类型
String mimeType = context.getMimeType(filename);
response.setHeader("content-type",mimeType);
//解決中文文件名問題
//获取user-agent请求头
String agent = request.getHeader("user-agent");
//使用工具类方法编码文件名即可
filename = DownLoadUtils.getFileName(agent,filename);
//设置响应头的打开方式
response.setHeader("content-disposition","attachment;filename="+filename);
//将输入流的数据写出到输出流中
ServletOutputStream sos = response.getOutputStream();
byte[] buff = new byte[1024];
int len = 0;
while((len=fis.read(buff))!=-1){
sos.write(buff,0,len);
}
fis.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
<html>
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/18-Http-Response/img/猫咪.jpg">图片1</a>
<a href="/18-Http-Response/img/1.mp3">音乐</a>
<a href="/18-Http-Response/img/2.avi">视频</a>
<a href="/18-Http-Response/DownLoadServlet?filename=猫咪.jpg">图片1</a>
<a href="/18-Http-Response/DownLoadServlet?filename=2.avi">视频</a>
<a href="/18-Http-Response/DownLoadServlet?filename=1.mp3">音乐</a>
</body>
</html>
