Spring Security3.0怎么用js获得是否已经登录了而且获得登录数据

Java code

  Level: DEBUG   Time: 2011-01-29 20:46:38,140 Method: org.springframework.security.access.intercept.AbstractSecurityInterceptor.authenticateIfRequired(AbstractSecurityInterceptor.java:292)Message: Previously Authenticated: org.springframework.security.authentication.UsernamePasswordAuthenticationToken@65acf777: Principal: org.springframework.security.core.userdetails.User@0: Username: admin; Password: [PROTECTED]; Enabled: true; AccountNonExpired: true; credentialsNonExpired: true; AccountNonLocked: true; Granted Authorities: Admin_role; Password: [PROTECTED]; Authenticated: true; Details: org.springframework.security.web.authentication.WebAuthenticationDetails@1c07a: RemoteIpAddress: 127.0.0.1; SessionId: 4DA3893BAD3E43930D5FDCDF790E763C; Granted Authorities: Admin_roleObject:FilterInvocation: URL: //index.jsp

我用log4j记录日志文件的时候发现security中可以获得IP而且我想做个用js判断是不是已经登录了！问下大家这个该怎么弄？
能不能讲详细点。

[解决办法]
唉悲哀啊