public class UploadServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	public int generateRandomNumber(int start, int end) {
		Random random = new Random();
		long fraction = (long) ((end - start + 1) * random.nextDouble());
		return ((int) (fraction + start));
	}

	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// gets values of text fields
		String id_Przedmiotu = request.getParameter("ID");

		InputStream inputStream = null; // input stream of the upload file
		int liczba = generateRandomNumber(1000, 8888);
		// obtains the upload file part in this multipart request
		Part filePart = request.getPart("photo");
		if (filePart != null) {
			// prints out some information for debugging
			System.out.println(filePart.getName());
			System.out.println(filePart.getSize());
			System.out.println(filePart.getContentType());

			// obtains input stream of the upload file
			inputStream = filePart.getInputStream();
		}

		Connection conn = null; // connection to the database
		String message = null; // message will be sent back to client

		try {
			// connects to the database
			DriverManager.registerDriver(new com.mysql.jdbc.Driver());
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/elearning", "root", "");
			// constructs SQL statement

			String sql = "INSERT INTO dokumentyprzedmiotu (ID_Dokumentu, ID_Przedmiotu, adress) values (?, ?, ?)";
			PreparedStatement statement = conn.prepareStatement(sql);
			statement.setInt(1, liczba);
			statement.setString(2, id_Przedmiotu);

			statement.setBlob(3, inputStream);

			int row = statement.executeUpdate();
			if (row > 0) {
				System.out.println("A contact was inserted with photo image.");
			}
			conn.close();
		} catch (SQLException ex) {
			ex.printStackTrace();
		} finally {
			if (conn != null) {
				// closes the database connection
				try {
					conn.close();
				} catch (SQLException ex) {
					ex.printStackTrace();
				}
			}
			System.out.println(message);
			response.sendRedirect("success.jsp");
		}
	}
}