在JSP中,pageContext、request、session、application均提供了存取数据的通用方法,假设已经在session中存入了名为"currentUser"的User对象, 则取出该数据的正确语句是( ) A. User user = session.getAttribute("currentUser"); B. User user = (User)session.getAttribute("currentUser"); C. Object user = session.getAttribute("currentUser"); D. String user = (String)session.getAttribute("currentUser");