Root cause:

java.lang.IllegalArgumentException: Can not set java.lang.Long field its.fractal.entity.Project.idProject to java.util.ArrayList
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:146)
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:150)
at java.lang.reflect.Field.get(Field.java:358)
at org.hibernate.property.DirectPropertyAccessor$DirectGetter.get(DirectPropertyAccessor.java:32)
at org.hibernate.tuple.entity.AbstractEntityTuplizer.getIdentifier(AbstractEntityTuplizer.java:183)
at org.hibernate.persister.entity.AbstractEntityPersister.getIdentifier(AbstractEntityPersister.java:3539)
at org.hibernate.persister.entity.AbstractEntityPersister.isTransient(AbstractEntityPersister.java:3255)
at org.hibernate.engine.ForeignKeys.isTransient(ForeignKeys.java:181)
at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:218)
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:397)
at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:87)
at org.hibernate.param.PositionalParameterSpecification.bind(PositionalParameterSpecification.java:39)
at org.hibernate.loader.hql.QueryLoader.bindParameterValues(QueryLoader.java:503)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1554)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.doList(Loader.java:2211)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2095)
at org.hibernate.loader.Loader.list(Loader.java:2090)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:388)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:338)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:172)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1121)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
at org.springframework.orm.hibernate3.HibernateTemplate$33.doInHibernate(HibernateTemplate.java:948)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:374)
at org.springframework.orm.hibernate3.HibernateTemplate.findByNamedQuery(HibernateTemplate.java:939)
at its.fractal.hibernate.UserHibernateDao.getActivityByUserAndDateInterval(UserHibernateDao.java:148)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy27.getActivityByUserAndDateInterval(Unknown Source)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.proxy.LazyInitProxyFactory$JdkHandler.invoke(LazyInitProxyFactory.java:416)
at org.apache.wicket.proxy.$Proxy78.getActivityByUserAndDateInterval(Unknown Source)
at its.fractal.admin.StatisticUsers$SubmitCalendarButton.onSubmit(StatisticUsers.java:203)
at org.apache.wicket.markup.html.form.Form.delegateSubmit(Form.java:1561)
at org.apache.wicket.markup.html.form.Form.process(Form.java:958)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:920)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:319)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:244)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:383)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:288)
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:662)

Complete stack:

org.apache.wicket.WicketRuntimeException: Method onFormSubmitted of interface org.apache.wicket.markup.html.form.IFormSubmitListener targeted at component [MarkupContainer [Component id = formDate]] threw an exception
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:193)
at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)

org.springframework.orm.hibernate3.HibernateSystemException: could not get a field value by reflection getter of its.fractal.entity.Project.idProject; nested exception is org.hibernate.PropertyAccessException: could not get a field value by reflection getter of its.fractal.entity.Project.idProject
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:661)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:379)
at org.springframework.orm.hibernate3.HibernateTemplate.findByNamedQuery(HibernateTemplate.java:939)
at its.fractal.hibernate.UserHibernateDao.getActivityByUserAndDateInterval(UserHibernateDao.java:148)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy27.getActivityByUserAndDateInterval(Unknown Source)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.proxy.LazyInitProxyFactory$JdkHandler.invoke(LazyInitProxyFactory.java:416)
at org.apache.wicket.proxy.$Proxy78.getActivityByUserAndDateInterval(Unknown Source)
at its.fractal.admin.StatisticUsers$SubmitCalendarButton.onSubmit(StatisticUsers.java:203)
at org.apache.wicket.markup.html.form.Form.delegateSubmit(Form.java:1561)
at org.apache.wicket.markup.html.form.Form.process(Form.java:958)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:920)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)

org.hibernate.PropertyAccessException: could not get a field value by reflection getter of its.fractal.entity.Project.idProject
at org.hibernate.property.DirectPropertyAccessor$DirectGetter.get(DirectPropertyAccessor.java:35)
at org.hibernate.tuple.entity.AbstractEntityTuplizer.getIdentifier(AbstractEntityTuplizer.java:183)
at org.hibernate.persister.entity.AbstractEntityPersister.getIdentifier(AbstractEntityPersister.java:3539)
at org.hibernate.persister.entity.AbstractEntityPersister.isTransient(AbstractEntityPersister.java:3255)
at org.hibernate.engine.ForeignKeys.isTransient(ForeignKeys.java:181)
at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:218)
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:397)
at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:87)
at org.hibernate.param.PositionalParameterSpecification.bind(PositionalParameterSpecification.java:39)
at org.hibernate.loader.hql.QueryLoader.bindParameterValues(QueryLoader.java:503)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1554)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.doList(Loader.java:2211)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2095)
at org.hibernate.loader.Loader.list(Loader.java:2090)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:388)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:338)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:172)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1121)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
at org.springframework.orm.hibernate3.HibernateTemplate$33.doInHibernate(HibernateTemplate.java:948)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:374)
at org.springframework.orm.hibernate3.HibernateTemplate.findByNamedQuery(HibernateTemplate.java:939)
at its.fractal.hibernate.UserHibernateDao.getActivityByUserAndDateInterval(UserHibernateDao.java:148)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy27.getActivityByUserAndDateInterval(Unknown Source)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.proxy.LazyInitProxyFactory$JdkHandler.invoke(LazyInitProxyFactory.java:416)
at org.apache.wicket.proxy.$Proxy78.getActivityByUserAndDateInterval(Unknown Source)
at its.fractal.admin.StatisticUsers$SubmitCalendarButton.onSubmit(StatisticUsers.java:203)
at org.apache.wicket.markup.html.form.Form.delegateSubmit(Form.java:1561)
at org.apache.wicket.markup.html.form.Form.process(Form.java:958)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:920)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)