从AEM6.0升级到AEM6.1后，ACS Not Found页面不再有效。如果我专门访问错误页面（/content/PROJECT/en/errors/404.html），那么它呈现并且一切正常。我不确定应采取哪些措施来解决这个问题。
28.10.2015 15:43:42.247 *ERROR* [10.43.32.4 [1446061422243] GET /notapage HTTP/1.1] org.apache.sling.engine.impl.DefaultErrorHandler Error handler failed:java.io.IOException
java.io.IOException: Error handler failed: java.lang.Error
at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:771)
at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:442)
at org.apache.sling.engine.impl.DefaultErrorHandler.handleError(DefaultErrorHandler.java:96)
at org.apache.sling.engine.impl.SlingRequestProcessorImpl$1.render(SlingRequestProcessorImpl.java:345)
at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:77)
at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
at org.apache.sling.rewriter.impl.RewriterFilter.doFilter(RewriterFilter.java:83)
at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
at org.apache.sling.engine.impl.SlingRequestProcessorImpl.handleError(SlingRequestProcessorImpl.java:352)
at org.apache.sling.engine.impl.SlingRequestProcessorImpl.doProcessRequest(SlingRequestProcessorImpl.java:167)
at org.apache.sling.engine.impl.SlingMainServlet.service(SlingMainServlet.java:217)
at org.apache.felix.http.base.internal.handler.ServletHandler.doHandle(ServletHandler.java:336)
at org.apache.felix.http.base.internal.handler.ServletHandler.handle(ServletHandler.java:297)
at org.apache.felix.http.base.internal.dispatch.ServletPipeline.handle(ServletPipeline.java:93)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:50)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at com.adobe.granite.license.impl.LicenseCheckFilter.doFilter(LicenseCheckFilter.java:308)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.sling.security.impl.ReferrerFilter.doFilter(ReferrerFilter.java:290)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.felix.http.sslfilter.internal.SslFilter.doFilter(SslFilter.java:89)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.sling.featureflags.impl.FeatureManager.doFilter(FeatureManager.java:115)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.sling.engine.impl.log.RequestLoggerFilter.doFilter(RequestLoggerFilter.java:75)
at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
at org.apache.felix.http.base.internal.dispatch.FilterPipeline.dispatch(FilterPipeline.java:76)
at org.apache.felix.http.base.internal.dispatch.Dispatcher.dispatch(Dispatcher.java:49)
at org.apache.felix.http.base.internal.DispatcherServlet.service(DispatcherServlet.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:497)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.Error: Unresolved compilation problems:
The type com.day.cq.wcm.api.Page cannot be resolved. It is indirectly referenced from required .class files
The type com.day.cq.wcm.api.designer.Style cannot be resolved. It is indirectly referenced from required .class files
The type com.day.cq.wcm.api.components.ComponentContext cannot be resolved. It is indirectly referenced from required .class files
The type com.day.cq.wcm.api.components.Component cannot be resolved. It is indirectly referenced from required .class files
Only a type can be imported. com.day.cq.wcm.api.Page resolves to a package
Only a type can be imported. com.day.cq.wcm.api.NameConstants resolves to a package
Only a type can be imported. com.day.cq.wcm.api.PageManager resolves to a package
Only a type can be imported. com.day.cq.wcm.api.designer.Designer resolves to a package
Only a type can be imported. com.day.cq.wcm.api.designer.Design resolves to a package
Only a type can be imported. com.day.cq.wcm.api.designer.Style resolves to a package
Only a type can be imported. com.day.cq.wcm.api.components.ComponentContext resolves to a package
Only a type can be imported. com.day.cq.wcm.api.components.EditContext resolves to a package
Only a type can be imported. com.day.cq.wcm.api.WCMMode resolves to a package
com.day.cq.wcm.api.components.ComponentContext cannot be resolved to a type
com.day.cq.wcm.api.components.EditContext cannot be resolved to a type
com.day.cq.wcm.api.PageManager cannot be resolved to a type
com.day.cq.wcm.api.Page cannot be resolved to a type
com.day.cq.wcm.api.Page cannot be resolved to a type
com.day.cq.wcm.api.components.Component cannot be resolved to a type
com.day.cq.wcm.api.designer.Designer cannot be resolved to a type
com.day.cq.wcm.api.designer.Design cannot be resolved to a type
com.day.cq.wcm.api.designer.Design cannot be resolved to a type
com.day.cq.wcm.api.designer.Style cannot be resolved to a type
com.day.cq.wcm.api.components.ComponentContext cannot be resolved to a type
com.day.cq.wcm.api.components.EditContext cannot be resolved to a type
com.day.cq.wcm.api.PageManager cannot be resolved to a type
com.day.cq.wcm.api.Page cannot be resolved to a type
com.day.cq.wcm.api.Page cannot be resolved to a type
com.day.cq.wcm.api.components.Component cannot be resolved to a type
com.day.cq.wcm.api.designer.Designer cannot be resolved to a type
com.day.cq.wcm.api.designer.Design cannot be resolved to a type
com.day.cq.wcm.api.designer.Design cannot be resolved to a type
com.day.cq.wcm.api.designer.Style cannot be resolved to a type
WCMMode cannot be resolved
WCMMode.DISABLED cannot be resolved to a type
at org.apache.jsp.apps.sling.servlet.errorhandler._404_jsp.<init>(_404_jsp.java:1)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at java.lang.Class.newInstance(Class.java:379)
at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.loadServlet(JspServletWrapper.java:165)
at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.prepareServlet(JspServletWrapper.java:434)
at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:486)
at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:449)
at org.apache.sling.scripting.jsp.JspScriptEngineFactory.callJsp(JspScriptEngineFactory.java:284)
at org.apache.sling.scripting.jsp.JspScriptEngineFactory.access$100(JspScriptEngineFactory.java:102)
at org.apache.sling.scripting.jsp.JspScriptEngineFactory$JspScriptEngine.eval(JspScriptEngineFactory.java:536)
at org.apache.sling.scripting.core.impl.DefaultSlingScript.call(DefaultSlingScript.java:361)
at org.apache.sling.scripting.core.impl.DefaultSlingScript.eval(DefaultSlingScript.java:171)
at org.apache.sling.scripting.core.impl.DefaultSlingScript.service(DefaultSlingScript.java:463)
at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:762)
... 67 common frames omitted