Java实现文件的上传和下载

文件的上传

@WebServlet("/up")
@MultipartConfig  //使用MultipartConfig注解标注改servlet能够接受文件上传的请求
public class UploadServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        Part part = req.getPart("myfile");
        String disposition = part.getHeader("Content-Disposition");
        String suffix = disposition.substring(disposition.lastIndexOf("."),disposition.length()-1);
          //随机的生存一个32的字符串
        String filename = UUID.randomUUID()+suffix;
          //获取上传的文件名
        InputStream is = part.getInputStream();
        //动态获取服务器的路径
        String serverpath = req.getServletContext().getRealPath("upload");
        FileOutputStream fos = new FileOutputStream(serverpath+"/"+filename);
        byte[] bty = new byte[1024];
        int length =0;
        while((length=is.read(bty))!=-1){
            fos.write(bty,0,length);
        }
        fos.close();
        is.close();
    }
}

文件的下载

public class DownServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String file = request.getParameter("file"); //客户端传递的需要下载的文件名
        String path = request.getServletContext().getRealPath("")+"/"+file; //默认认为文件在当前项目的根目录
        FileInputStream fis = new FileInputStream(path);
        response.setCharacterEncoding("utf-8");
        response.setHeader("Content-Disposition", "attachment; filename="+file);
        ServletOutputStream out = response.getOutputStream();
        byte[] bt = new byte[1024];
        int length = 0;
        while((length=fis.read(bt))!=-1){
            out.write(bt,0,length);
        }
        out.close();
    }
}