Error CAS Liferay integration

[marco romero romero，修改在15 年前。]

Hi!
First of all, sorry, but my english is not very well.
I'm having problems before the integration of liferay 5.1 with CAS.

The sign in and sign out functions work ok, but when the sign in is made the initial page is loaded without any style (it seems that
the page has not loaded CSS styles).

I paste here the error:

ERROR [CASFilter:60] java.lang.NullPointerException
java.lang.NullPointerException
at com.liferay.portal.servlet.filters.sso.cas.CASFilter.processFilter(CA
SFilter.java:121)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java
:71)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:188)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter
.java:132)
at com.liferay.portal.servlet.filters.virtualhost.VirtualHostFilter.doFi
lter(VirtualHostFilter.java:185)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:188)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter
.java:132)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java
:74)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:188)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewrit
eFilter.java:738)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:174)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(Authentica
torBase.java:433)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:174)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:874)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.p
rocessConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpo
int.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFol
lowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP
ool.java:689)
at java.lang.Thread.run(Unknown Source)

Please, can anyone help me with this? I have been working at this for about two days and I can't find where could be the problem!!

Best regards and thanks in advance!!