javaweb文件上传下载

JavaWeb 文件上传下载可以通过以下步骤实现：

1. 文件上传

1.1 在表单中添加文件选择框

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

1.2 编写上传文件的 Servlet

@WebServlet("/upload")
@MultipartConfig
public class UploadServlet extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        Part filePart = request.getPart("file");
        String fileName = filePart.getSubmittedFileName();
        InputStream fileContent = filePart.getInputStream();
        // 处理上传的文件
    }
}

2. 文件下载

2.1 在页面中添加下载链接

<a href="download?fileName=example.txt">下载</a>

2.2 编写下载文件的 Servlet

@WebServlet("/download")
public class DownloadServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String fileName = request.getParameter("fileName");
        File file = new File("path/to/files/" + fileName);
        response.setContentType("application/octet-stream");
        response.setContentLength((int) file.length());
        response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        try (InputStream in = new FileInputStream(file); OutputStream out = response.getOutputStream()) {
            byte[] buffer = new byte[1024];
            int length;
            while ((length = in.read(buffer)) > 0) {
                out.write(buffer, 0, length);
            }
        }
    }
}

以上就是 JavaWeb 文件上传下载的实现方法。