The Servlet and JSP specs do not make any special provisions for multipart requests (file uploads).
Servlet and JSP developers either have to depend on third party libraries or make their own framework for this. Fabricating own framework is just like re-inventing the wheel. Fortunately, there are several, very good, open source ones out there; with clear instructions and code examples.
The two most popular are Jakarta Commons FileUpload and com.oreilly.servlet
(Note: request.getParameter() would always return null when dealing with multipart/form-data.)