yelu cas 在cas服务器视图(jsp页面)中获取登陆名

<%
org.jasig.cas.authentication.principal.UsernamePasswordCredentials a=(org.jasig.cas.authentication.principal.UsernamePasswordCredentials)request.getAttribute("credentials");
if (a==null){
    out.print("null");
}else{
    out.print("not  null："+a.getClass().getName());
    out.print("帐号："+a.getUsername()); 
}
 %>