1、html网页，超链接交由Servlet处理
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<h1>实现文件的下载功能</h1>
<a href="ImgServlet?filename=a.jpg">aa</a><br>
<a href="ImgServlet?filename=b.jpg">bb </a><br>
<a href="ImgServlet?filename=图片.png">图片</a><br>
</body>
</body>
</html>
2.web.xml----Servlet的注册
<servlet>
<servlet-name>DownLoadImgServlet</servlet-name>。--1
<servlet-class>nee.DownLoadImgServlet</servlet-class> --这是我自己的路径
</servlet>
<servlet-mapping>
<servlet-name>DownLoadImgServlet</servlet-name>--2
<url-pattern>/ImgServlet</url-pattern>--网页的映射，对应html上a的超链接
</servlet-mapping>
--1 2 处名字必须相同
3.Servlet的实现
package nee;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;
@WebServlet(name = "DownLoadImgServlet")
public class DownLoadImgServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
用字节输出流向文件写资源
资源需要从输入流中读入
输入流为图片构成的输入流
*/
String filename=request.getParameter("filename");
//解决中文找不到资源路径的问题
filename = new String(filename.getBytes("ISO-8859-1"),"UTF-8");
//将文件转化为输入流
InputStream is=getServletContext().getResourceAsStream("download/"+filename);
//解决文件名不显示中文的问题
filename=URLEncoder.encode(filename,"UTF-8");
//声明这是一个下载的文件
response.setHeader("Content-Disposition","attachment;filename="+filename);
OutputStream os=response.getOutputStream();
int len=0;
byte[] buffer = new byte[1024];
while ((len=is.read(buffer) )!= -1){
os.write(buffer,0,len);
}
}
}