java目录里上传的代码

以下是 Java 中实现服务器目录上传文件的示例代码：

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@WebServlet("/upload")
@MultipartConfig(
    fileSizeThreshold = 1024 * 1024 * 2, // 2 MB
    maxFileSize = 1024 * 1024 * 10, // 10 MB
    maxRequestSize = 1024 * 1024 * 50 // 50 MB
)
public class FileUploadServlet extends HttpServlet {
    private static final String UPLOAD_DIRECTORY = "uploads";

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 创建上传文件夹
        String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY;
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        // 处理上传的文件
        for (Part part : request.getParts()) {
            String fileName = extractFileName(part);
            if (fileName != null && !fileName.isEmpty()) {
                String filePath = uploadPath + File.separator + fileName;
                File file = new File(filePath);
                try (InputStream inputStream = part.getInputStream()) {
                    Files.copy(inputStream, file.toPath());
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }

        response.sendRedirect(request.getContextPath() + "/success.jsp");
    }

    private String extractFileName(Part part) {
        String contentDisposition = part.getHeader("content-disposition");
        String[] items = contentDisposition.split(";");
        for (String item : items) {
            if (item.trim().startsWith("filename")) {
                return item.substring(item.indexOf("=") + 2, item.length() - 1);
            }
        }
        return null;
    }
}

这段代码实现了在服务器上创建名为 "uploads" 的上传文件夹，将用户上传的文件保存到该文件夹中。该代码使用了 Java Servlet 3.0 提供的 `@MultipartConfig` 注解，用于指定上传文件的大小限制。在上传文件时，该代码会遍历所有上传的文件，将每个文件保存到上传文件夹中。其中，`extractFileName` 方法用于从 HTTP 请求头中获取上传文件的文件名。