Java文件上传与文件下载实现方法详解

 public class RegisterServlet extends HttpServlet { private static final long serialVersionUID = 1L; public RegisterServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().append("Served at: ").append(request.getContextPath()); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //第一步、判断请求是否为multipart请求 if(!ServletFileUpload.isMultipartContent(request)) { throw new RuntimeException("当前请求只支持文件上传"); } try { //第二步、创建FileItem工厂 DiskFileItemFactory factory = new DiskFileItemFactory(); //设置临时文件存储目录 String path = this.getServletContext().getRealPath("/Temp"); File temp = new File(path); factory.setRepository(temp); //单位：字节。本例设置边界值为2MB，超过该值会创建临时文件 factory.setSizeThreshold(1024*1024*2); //第三步、创建文件上传核心组件 ServletFileUpload upload = new ServletFileUpload(factory); //设置item的头部字符编码，解决中文乱码问题 upload.setHeaderEncoding("utf-8"); //设置单个上传文件的最大值为5MB upload.setFileSizeMax(1024*1024*5); //设置一次上传所有文件总和的最大值为10MB（上传多个文件时起作用） upload.setFileSizeMax(1024*1024*10); //第四步、解析请求获取所有的item List items = upload.parseRequest(request); //第五步、遍历item for(FileItem item:items) { if (item.isFormField()) { processFormField(item); } else { processUploadedFile(item); } } } catch (FileUploadException e) { e.printStackTrace(); } } private void processFormField(FileItem item) { try { String name = item.getFieldName(); //解决中文乱码问题 String value = item.getString("utf-8"); System.out.println(name+"="+value); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } } private void processUploadedFile(FileItem item) { try { InputStream inputStream = item.getInputStream(); String fieldName = item.getFieldName(); //获取上传文件原始名称 String fileName = item.getName(); //解决文件同名问题 fileName = System.currentTimeMillis()+fileName; String contentType = item.getContentType(); boolean isInMemory = item.isInMemory(); long sizeInBytes = item.getSize(); String path = this.getServletContext().getRealPath("/UploadContent"); //Date now = new Date(); Calendar now = Calendar.getInstance(); //对上传的文件进行分类管理 path += "/"+now.get(Calendar.YEAR)+"/"+(now.get(Calendar.MONTH)+1)+"/"+now.get(Calendar.DAY_OF_MONTH); //若目录不存在，则创建该目录 File directory = new File(path); if(!directory.exists()) { directory.mkdirs(); } File descFile = new File(path,fileName); OutputStream outputStream = new FileOutputStream(descFile); int length = -1; byte[] buffer = new byte[1024]; while((length=inputStream.read(buffer))!=-1) { outputStream.write(buffer, 0, length); } outputStream.close(); inputStream.close(); //删除临时文件 item.delete(); } catch (IOException e) { e.printStackTrace(); } } } 

 public class DownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; public DownloadServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //设置响应的头部属性content-disposition值为attachment //使用filename来指定文件名 String filename = "超跑.png-600"; byte[] bytes = filename.getBytes("utf-8"); //http协议规定浏览器只能接受ISO8859-1类型的字节数据 filename = new String(bytes,"ISO8859-1"); response.setHeader("content-disposition", "attachment;filename="+filename); //获取连接服务器资源文件的输入流 InputStream is = request.getServletContext().getResourceAsStream("/Resources/BS架构原理图1.png-600"); //获取输出流 ServletOutputStream os = response.getOutputStream(); //将输入流中的数据写到输出流中 int length = -1; byte[] buffer = new byte[1024]; while((length=is.read(buffer))!=-1) { os.write(buffer,0,length); } os.close(); is.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }