jsp上传与下载

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

<%@ page import="java.io.*, java.util.*, javax.servlet.http.*" %>
<%@ page import="org.apache.commons.fileupload.*, org.apache.commons.fileupload.disk.*, org.apache.commons.fileupload.servlet.*" %>
<%@ page import="org.apache.commons.io.output.*" %>

<%
    boolean isMultipart = ServletFileUpload.isMultipartContent(request);
    if (!isMultipart) {
        out.println("No file uploaded");
        return;
    }

    DiskFileItemFactory factory = new DiskFileItemFactory();
    ServletFileUpload upload = new ServletFileUpload(factory);

    List<FileItem> items = upload.parseRequest(request);
    for (FileItem item : items) {
        if (!item.isFormField()) {
            String fileName = item.getName();
            File uploadedFile = new File(application.getRealPath("/uploads") + "/" + fileName);
            item.write(uploadedFile);
            out.println("File uploaded successfully: " + fileName);
        }
    }
%>

<%@ page import="java.io.*" %>
<%
    String filePath = application.getRealPath("/uploads") + "/" + request.getParameter("filename");
    File file = new File(filePath);

    if (file.exists()) {
        response.setContentType("application/octet-stream");
        response.setHeader("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"");

        try (InputStream in = new FileInputStream(file);
             OutputStream outStream = response.getOutputStream()) {

            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = in.read(buffer)) != -1) {
                outStream.write(buffer, 0, bytesRead);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    } else {
        out.println("File not found");
    }
%>