1.在session中取得spring security的登录用户名如下：

${session.SPRING_SECURITY_CONTEXT.authentication.principal.username}

       spring security 把SPRING_SECURITY_CONTEXT 放入了session 没有直接把username 放进去。下面一段代码主要描述的是session中的存的变量，

存跳转时候的URLsession {SPRING_SECURITY_SAVED_REQUEST_KEY=SavedRequest[http://localhost:8080/AVerPortal/resourceAction/resourceIndex.action]}
存的是登录成功时候session中存的信息：

        session {SPRING_SECURITY_CONTEXT=org.springframework.security.context.SecurityContextImpl@87b16984: Authentication: org.springframework.security.providers.cas.CasAuthenticationToken@87b16984:Principal: com.avi.casExtends.UserInfo@ff631d80: Username: test; Password: [PROTECTED]; Enabled: true; AccountNonExpired: true; credentialsNonExpired: true; AccountNonLocked: true; Granted Authorities: ROLE_ADMIN; Password: [PROTECTED]; Authenticated: true;Details: org.springframework.security.ui.WebAuthenticationDetails@12afc: RemoteIpAddress: 127.0.0.1; SessionId: AE56E8925195DFF4C50ABD384574CCEA; Granted Authorities: ROLE_ADMIN Assertion: org.jasig.cas.client.validation.AssertionImpl@661a11 Credentials (Service/ProxyTicket): ST-3-1lX3acgZ6HNgmhvjXuxB-cas, userId=2, userName=test}

2.在页面端用tag获取：

<%@ taglib prefix='security' uri='http://www.springframework.org/security/tags'%><security:authentication property="principal.username"></security:authentication> 

或者

<security:authorize ifAllGranted="ROLE_ADMIN"><security:authentication property="principal.username"></security:authentication> </security:authorize>

或者取session中的值：

${session.SPRING_SECURITY_CONTEXT.authentication.principal.username}

3.在后台获取

UserDetails userDetails = (UserDetails) SecurityContextHolder.getContext().getAuthentication().getPrincipal();userDetails.getUsername()

      如果想要获取更多的信息：得扩展userDetails的默认实现类user类和UserDetailsService接口

     由于springsecurity是把整个user信息放入session中的即：session.SPRING_SECURITY_CONTEXT.authentication.principal。这个就是代表着user对象。