protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取请求参数，文件名称
String filename = request.getParameter("filename");
//2.使用字节输入流加载文件
//2.1找到文件服务器路径
ServletContext sc = this.getServletContext();
String realPath = sc.getRealPath("/img/"+filename);
System.out.println(realPath);
//2.2用字节流关联
FileInputStream is = new FileInputStream(realPath);
//3.定义输出流
ServletOutputStream sos = response.getOutputStream();
//4.1获取响应头response
//4.1.1获取文件的类型，使用servletcontext.getMimeType
String mimeType = sc.getMimeType(filename);
//4.2设置响应头类型：content-type
response.setHeader("content-type",mimeType);
//4.3设置响应头content-disposition
response.setHeader("content-disposition","attachment;filename="+filename);
//4.定义缓冲区
byte[] bytes = new byte[1024];
int len = 0;
while ((len = is.read(bytes)) != -1){
sos.write(bytes);
}
is.close();
}
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/day15/img/1.jpg">图片1</a>
<a href="/day15/img/2.jpg">图片2</a>
<hr/>
<a href="/day15/downServlet?filename=1.jpg">图片1</a>
<a href="/day15/downServlet?filename=2.jpg">图片2</a>
</body>
</html>
