Servlet文件上传

@WebServlet(name = "DownloadServlet", value = "/DownloadServlet")
public class DownloadServlet extends HttpServlet {
    //如何将服务器上的资源返回给浏览器
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String filename = request.getParameter("filename");
        //如何通知浏览器不要预览，而是下载文件
        String mimeType = this.getServletContext().getMimeType(filename);//得到mime类型
        response.setContentType(mimeType);
        response.setHeader("Content-Disposition","attachment;filename=" + filename);

        //通过ServletContext对象获取文件的绝对路径
        String realPath = this.getServletContext().getRealPath("download/" + filename);
        InputStream in = new FileInputStream(realPath);
        ServletOutputStream outputStream = response.getOutputStream();

        //文件拷贝
        int len = 0;
        byte[] buffer = new byte[1024];
        while((len = in.read(buffer)) > 0){
            outputStream.write(buffer,0,len);
        }
        in.close();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
}