文件上传案例

• 朋友圈 ,邮箱上传附件.百度云盘 360云盘. 
• 代码实现过程: 
• 客户端要求: 
  • 要求form表单必须有一个文件上传项 
  • 请求的方式必须为post 因为get提交数据有大小的限制 
  • 必须加上一个enctype = multipart/form-data 否则请求体里面没有内容
• 服务器逻辑:

@MultipartConfig@WebServlet("/uploads")public class Upload extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        req.setCharacterEncoding("utf-8");        Part part = req.getPart("file");        String realPath = getServletContext().getRealPath("fileUpload");        System.out.println(realPath);        String header = part.getHeader("Content-Disposition");        String[] array = header.split(";");        String filename = array[array.length - 1];        String[] arr = filename.split("=");        String filerealname = arr[arr.length - 1];        String file = filerealname.substring(1, filerealname.length() - 1);        System.out.println(file);        System.out.println(realPath + "\\" + file);        part.write(realPath + "\\" + file);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}