scope=  "request"   "page"  "session"  "application"   (对应四个隐含对象)

<jsp:userBean id="user"

　　　　　　scope="request"

　　　　　　　　class=""/>

<%= user%><br>

<%= request.getAttribute("user")%>

和下面等价

User user = null;

user=request.getAttribute("user");

if(user==null){

user = new User();

request.setAttribute("user",user);

}

<%= user%><br>

<%= request.getAttribute("user")%>