就是那个3e5d开头的怎么回事

代码贴在下面了

package fun.nicely.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.List;
import java.util.UUID;

public class FileUploadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        resp.setCharacterEncoding("utf-8");
        PrintWriter out = resp.getWriter();
        File file = new File(req.getContextPath()+"\\TempFolder");
        if (!file.exists()) {
            file.mkdirs();
        }
        DiskFileItemFactory factory = new DiskFileItemFactory(1024*1024*10,file);

        ServletFileUpload upload = new ServletFileUpload(factory);
//        设置上传所有文件大小
        upload.setSizeMax(1024*1024*6);
//        设置上传单个文件大小
        upload.setFileSizeMax(1024*1024*4);
        List<FileItem> fileItems = null;
        try {
//            解析请求
            fileItems = upload.parseRequest(req);
        } catch (FileUploadException e) {
            e.printStackTrace();
        }
        for (FileItem fileItem : fileItems) {
            //判断是否是文件
            if (fileItem.isFormField()) {
                String name = fileItem.getFieldName();
                if (name.equals("username")) {
                    if (!fileItem.getString().equals("")) {
                        String value = fileItem.getString("UTF-8");
                        out.write("上传者"+value+"<br>");
                    }
                }
            }else {
                String fileName = fileItem.getName();
                if (!fileName.equals("")&& fileName!=null) {
                    out.write("上传的文件名是:"+fileName+"<br>");
                }
                fileName = fileName.substring(fileName.lastIndexOf("/")+1);
                String uploadPath = req.getServletContext().getRealPath("/upload/");
                File uploadPathFolder = new File(uploadPath);
                if (!uploadPathFolder.exists()) {
                    uploadPathFolder.mkdir();
                }
                File uploadFile = new File(uploadPath +UUID.randomUUID()+ fileName);
                if (!uploadFile.exists()) {
                    uploadFile.createNewFile();
                }
                InputStream is = fileItem.getInputStream();
                FileOutputStream fos = new FileOutputStream(uploadFile);
                int len = 0;
                byte[] buffer = new byte[1024];
                while ((len = is.read(buffer))!=-1){
                    fos.write(buffer,0,len);
                }
                fos.close();
                is.close();
                out.write("文件"+fileName+"上传成功!<br>");
            }
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}