文件下载案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a id="tu" href="/img/3.jpg">图片</a>
<hr>
<a id="tu2" href="/downloadServlet?filename=3.jpg">图片2</a>
<script>
window.onload = function () {
var tu = document.getElementById("tu");
tu.onclick = function () {
}
}
</script>
</body>
</html>
@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
String contextPath = req.getContextPath();
//1、获取请求参数，文件名
String filename = req.getParameter("filename");
System.out.println("filename---"+filename);
//2使用字节输入流加载文件进内存
//2.1 找到文件服务器路径
ServletContext servletContext = this.getServletContext();
String realPath = servletContext.getRealPath("/img/" + filename);
System.out.println("realPath--"+realPath);
//2.2使用字节流关联
FileInputStream fis = new FileInputStream(realPath);
//3设置response响应头
//3.1设置相应头类型，content-type
String mimeType = servletContext.getMimeType(filename);
System.out.println("mimeType---"+mimeType);
resp.setHeader("content-type",mimeType);
//3.2设置响应头打开方式content-disposition
resp.setHeader("content-disposition","attachment;finame="+filename);
//4将输入流的数据写入到输出流
ServletOutputStream sos = resp.getOutputStream();
byte[] bytes = new byte[1024 * 8];
int len = 0;
while ((len = fis.read(bytes)) != -1){
sos.write(bytes,0,len);
}
if (fis != null){
fis.close();
}
}
}