我有时间从liferay获得此异常，这里是stacktrace：
07:45:02,033 ERROR [BasePersistenceImpl:186] Caught unexpected exception java.lang.NullPointerException
07:45:02,035 ERROR [BasePersistenceImpl:186] Caught unexpected exception com.liferay.portal.kernel.exception.SystemException
07:45:02,040 ERROR [MainServlet:1184] com.liferay.portal.kernel.events.ActionException: com.liferay.portal.kernel.exception.SystemException: com.liferay.portal.kernel.exception.SystemException: java.la
com.liferay.portal.kernel.events.ActionException: com.liferay.portal.kernel.exception.SystemException: com.liferay.portal.kernel.exception.SystemException: java.lang.NullPointerException
at com.liferay.portal.events.ServicePreAction.run(ServicePreAction.java:1241)
at com.liferay.portal.events.EventsProcessorImpl.processEvent(EventsProcessorImpl.java:81)
at com.liferay.portal.events.EventsProcessorImpl.process(EventsProcessorImpl.java:58)
at com.liferay.portal.events.EventsProcessorUtil.process(EventsProcessorUtil.java:53)
at com.liferay.portal.servlet.MainServlet.processServicePre(MainServlet.java:1164)
at com.liferay.portal.servlet.MainServlet.service(MainServlet.java:474)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:113)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:113)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:113)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:199)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.autologin.AutoLoginFilter.processFilter(AutoLoginFilter.java:240)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:71)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
at com.liferay.portal.servlet.FriendlyURLServlet.service(FriendlyURLServlet.java:135)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.strip.StripFilter.processFilter(StripFilter.java:304)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:113)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.gzip.GZipFilter.processFilter(GZipFilter.java:123)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:199)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:113)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.etag.ETagFilter.processFilter(ETagFilter.java:55)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.autologin.AutoLoginFilter.processFilter(AutoLoginFilter.java:240)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:71)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
at com.liferay.portal.servlet.I18nServlet.service(I18nServlet.java:102)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.sso.ntlm.NtlmPostFilter.processFilter(NtlmPostFilter.java:83)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.sharepoint.SharepointFilter.processFilter(SharepointFilter.java:80)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:121)
at com.liferay.portal.servlet.filters.virtualhost.VirtualHostFilter.processFilter(VirtualHostFilter.java:208)
at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:48)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:184)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:92)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:738)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:203)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:105)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:164)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:92)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:164)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:92)
at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:71)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:169)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:168)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:928)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:539)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:298)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: com.liferay.portal.kernel.exception.SystemException: com.liferay.portal.kernel.exception.SystemException: java.lang.NullPointerException
at com.liferay.portal.service.persistence.impl.BasePersistenceImpl.processException(BasePersistenceImpl.java:193)
at com.liferay.counter.service.persistence.CounterFinderImpl._competeIncrement(CounterFinderImpl.java:360)
at com.liferay.counter.service.persistence.CounterFinderImpl.increment(CounterFinderImpl.java:109)
at com.liferay.counter.service.persistence.CounterFinderImpl.increment(CounterFinderImpl.java:99)
at com.liferay.counter.service.impl.CounterLocalServiceImpl.increment(CounterLocalServiceImpl.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:112)
at com.liferay.portal.spring.transaction.TransactionInterceptor.invoke(TransactionInterceptor.java:71)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:108)
at com.liferay.portal.spring.aop.ServiceBeanAopProxy.invoke(ServiceBeanAopProxy.java:211)
at $Proxy114.increment(Unknown Source)
at com.liferay.portal.service.impl.LayoutLocalServiceImpl.getNextLayoutId(LayoutLocalServiceImpl.java:1161)
at com.liferay.portal.service.impl.LayoutLocalServiceImpl.addLayout(LayoutLocalServiceImpl.java:196)
at com.liferay.portal.service.impl.LayoutLocalServiceImpl.addLayout(LayoutLocalServiceImpl.java:393)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:112)
at com.liferay.portal.service.impl.LayoutLocalServiceVirtualLayoutsAdvice.invoke(LayoutLocalServiceVirtualLayoutsAdvice.java:144)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:108)
at com.liferay.portal.service.impl.LayoutLocalServiceStagingAdvice.invoke(LayoutLocalServiceStagingAdvice.java:90)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:108)
at com.liferay.portal.spring.transaction.TransactionInterceptor.invoke(TransactionInterceptor.java:71)
at com.liferay.portal.spring.aop.ServiceBeanMethodInvocation.proceed(ServiceBeanMethodInvocation.java:108)
at com.liferay.portal.spring.aop.ServiceBeanAopProxy.invoke(ServiceBeanAopProxy.java:211)
at $Proxy26.addLayout(Unknown Source)
at com.liferay.portal.service.LayoutLocalServiceUtil.addLayout(LayoutLocalServiceUtil.java:410)
at com.liferay.portal.events.ServicePreAction.addDefaultUserPrivateLayoutByProperties(ServicePreAction.java:1284)
at com.liferay.portal.events.ServicePreAction.addDefaultUserPrivateLayouts(ServicePreAction.java:1368)
at com.liferay.portal.events.ServicePreAction.updateUserLayouts(ServicePreAction.java:1979)
at com.liferay.portal.events.ServicePreAction.initThemeDisplay(ServicePreAction.java:371)
at com.liferay.portal.events.ServicePreAction.servicePre(ServicePreAction.java:1885)
at com.liferay.portal.events.ServicePreAction.run(ServicePreAction.java:1238)
... 116 more
Caused by: com.liferay.portal.kernel.exception.SystemException: java.lang.NullPointerException
at com.liferay.portal.service.persistence.impl.BasePersistenceImpl.processException(BasePersistenceImpl.java:193)
at com.liferay.counter.service.persistence.CounterFinderImpl._obtainIncrement(CounterFinderImpl.java:403)
at com.liferay.counter.service.persistence.CounterFinderImpl._competeIncrement(CounterFinderImpl.java:350)
... 151 more
Caused by: java.lang.NullPointerException
at com.liferay.counter.service.persistence.CounterFinderImpl._obtainIncrement(CounterFinderImpl.java:384)
... 152 more
在浏览器中：
an-unexpected-system-error-occurred
com.liferay.portal.kernel.exception.SystemException: com.liferay.portal.kernel.exception.SystemException: java.lang.NullPointerException
我找不到理由。此错误随机发生。有谁能够帮我？