jsp文件上传下载

<form action="upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file" />
    <input type="submit" value="Upload" />
</form>

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class FileUploadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        if (ServletFileUpload.isMultipartContent(request)) {
            try {
                List<FileItem> multiparts = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
                for (FileItem item : multiparts) {
                    if (!item.isFormField()) {
                        String name = new File(item.getName()).getName();
                        item.write(new File("/path/to/upload/directory/" + name));
                    }
                }
                response.sendRedirect("success.jsp");
            } catch (Exception ex) {
                request.setAttribute("message", "File Upload Failed due to " + ex);
                request.getRequestDispatcher("/result.jsp").forward(request, response);
            }
        } else {
            request.setAttribute("message", "Sorry this Servlet only handles file upload request");
            request.getRequestDispatcher("/result.jsp").forward(request, response);
        }
    }
}

<a href="download?file=path/to/file">Download File</a>

public class FileDownloadServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String filePath = request.getParameter("file");
        File file = new File(filePath);
        if (file.exists()) {
            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"");
            Files.copy(file.toPath(), response.getOutputStream());
        } else {
            response.sendError(HttpServletResponse.SC_NOT_FOUND);
        }
    }
}