1
2<h:selectManyCheckbox    value="#{quizController.selectedMultipleAnswerIds[question.id]}">
3    <f:selectItems value="#{question.answers}" var="answer" itemLabel="#{answer.answerText}"
4        itemValue="#{answer.id}" />
5</h:selectManyCheckbox>
6<p:commandButton styleClass="redButton" value="Quiz auswerten!"
7                actionListener="#{quizController.evaluateQuiz}"
8                update="frontendForm" />

1
2private Map<Integer, List<String>> selectedMultipleAnswerIds;
3...
4for(List<String> list:selectedMultipleAnswerIds.values()) {
5    list.size();
6}

  1
  22012-08-15 08:23:16,852 ERROR [com.liferay.faces.bridge.context.ExceptionHandlerAjaxImpl] - java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
  3javax.faces.event.AbortProcessingException: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
  4    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:182)
  5    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
  6    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)
  7    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
  8    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
  9    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
 10    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
 11    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
 12    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
 13    at com.liferay.faces.bridge.lifecycle.LifecycleWrapper.execute(LifecycleWrapper.java:35)
 14    at com.liferay.faces.bridge.BridgePhaseResourceImpl.execute(BridgePhaseResourceImpl.java:99)
 15    at com.liferay.faces.bridge.BridgeImpl.doFacesRequest(BridgeImpl.java:116)
 16    at javax.portlet.faces.GenericFacesPortlet.serveResource(GenericFacesPortlet.java:178)
 17    at com.liferay.portlet.FilterChainImpl.doFilter(FilterChainImpl.java:118)
 18    at com.liferay.portal.kernel.portlet.PortletFilterUtil.doFilter(PortletFilterUtil.java:71)
 19    at com.liferay.portal.kernel.servlet.PortletServlet.service(PortletServlet.java:111)
 20    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 21    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
 22    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 23    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
 24    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73)
 25    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 26    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 27    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
 28    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)
 29    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)
 30    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
 31    at com.liferay.portlet.InvokerPortletImpl.invoke(InvokerPortletImpl.java:531)
 32    at com.liferay.portlet.InvokerPortletImpl.invokeResource(InvokerPortletImpl.java:626)
 33    at com.liferay.portlet.InvokerPortletImpl.serveResource(InvokerPortletImpl.java:436)
 34    at com.liferay.portal.action.LayoutAction.processPortletRequest(LayoutAction.java:1075)
 35    at com.liferay.portal.action.LayoutAction.processLayout(LayoutAction.java:719)
 36    at com.liferay.portal.action.LayoutAction.execute(LayoutAction.java:249)
 37    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
 38    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
 39    at com.liferay.portal.struts.PortalRequestProcessor.process(PortalRequestProcessor.java:176)
 40    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
 41    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
 42    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
 43    at com.liferay.portal.servlet.MainServlet.callParentService(MainServlet.java:560)
 44    at com.liferay.portal.servlet.MainServlet.service(MainServlet.java:537)
 45    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 46    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
 47    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 48    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
 49    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 50    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 51    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 52    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 53    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 54    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 55    at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:294)
 56    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
 57    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
 58    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
 59    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73)
 60    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 61    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 62    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
 63    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)
 64    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)
 65    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
 66    at com.liferay.portal.servlet.FriendlyURLServlet.service(FriendlyURLServlet.java:138)
 67    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 68    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
 69    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 70    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72)
 71    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 72    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 73    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 74    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 75    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 76    at com.liferay.portal.servlet.filters.gzip.GZipFilter.processFilter(GZipFilter.java:123)
 77    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
 78    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
 79    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
 80    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 81    at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:294)
 82    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
 83    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
 84    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
 85    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 86    at com.liferay.portal.servlet.filters.i18n.I18nFilter.processFilter(I18nFilter.java:241)
 87    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
 88    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
 89    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
 90    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 91    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 92    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
 93    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 94    at com.liferay.portal.servlet.filters.autologin.AutoLoginFilter.processFilter(AutoLoginFilter.java:246)
 95    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
 96    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
 97    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
 98    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
 99    at com.liferay.portal.servlet.filters.sso.ntlm.NtlmPostFilter.processFilter(NtlmPostFilter.java:83)
100    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
101    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
102    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
103    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
104    at com.liferay.portal.sharepoint.SharepointFilter.processFilter(SharepointFilter.java:80)
105    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
106    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
107    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
108    at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163)
109    at com.liferay.portal.servlet.filters.virtualhost.VirtualHostFilter.processFilter(VirtualHostFilter.java:216)
110    at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57)
111    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
112    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
113    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:187)
114    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95)
115    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
116    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
117    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
118    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
119    at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:738)
120    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206)
121    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108)
122    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:167)
123    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95)
124    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
125    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:167)
126    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95)
127    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116)
128    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:187)
129    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95)
130    at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73)
131    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
132    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
133    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
134    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
135    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
136    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
137    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
138    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
139    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
140    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
141    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
142    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
143    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
144    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
145    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
146    at java.lang.Thread.run(Thread.java:662)
147Caused by: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
148    at de.planetic.customer.d11503.liferay.portlet.quiz_portlet.controller.frontend.QuizController.evaluateQuiz(QuizController.java:156)
149    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
150    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
151    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
152    at java.lang.reflect.Method.invoke(Method.java:597)
153    at org.jboss.el.util.ReflectionUtil.invokeMethod(ReflectionUtil.java:328)
154    at org.jboss.el.util.ReflectionUtil.invokeMethod(ReflectionUtil.java:341)
155    at org.jboss.el.parser.AstPropertySuffix.invoke(AstPropertySuffix.java:58)
156    at org.jboss.el.parser.AstValue.invoke(AstValue.java:96)
157    at org.jboss.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
158    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:153)
159    ... 142 more

 1  // prepare list
 2  List<String> _list = new ArrayList<String>();
 3  _list.add("a");
 4  _list.add("b");
 5
 6  // convert list to array (dynamic way)
 7  String[] _array = (String[]) _list.toArray(new String[0]);
 8       
 9  // re-convert array to list (dynamic way)
10  _list = java.util.Arrays.asList(_array);