anchor.diff:            displayName = ((QQUser)user).getNickname();
         }
   %>
  +    <td> | </td>
       <td>
         Welcome【<%=displayName%>】
       </td>
  +    <td> | </td>
       <td>
         <a href="<%=request.getContextPath()+"/system/logout.jsp"%>">Sign out</a>
       </td>
  
positive.code:   User user = (User)session.getAttribute("user");
    if(user==null){
  %>
      <td>
        <a href="<%=request.getContextPath()%>/system/register.jsp">Sign up</a>
      </td>
      <td>
        <a href="<%=request.getContextPath()%>/system/login.jsp">Sign in</a>
      </td>
  
negative.code:   }
  %>
    </tr>
  </table>
  </h3>