[hibernate-users] Problem persisting a set of object

I have two questions: 1) I thought the entity at the source end of a OneToMany defined by annotations didn't care about it's collection and would ignore updates to the collection? (this is the first problem, I got around it by settings cascade = CascadeType.ALL because if it does persist it's list that's not a bad thing, it's just not what I was expecting) 2) After doing that, I get the following error. As far as I can tell all my Entities have generated ids, so I don't really undefrstand how I could have an object with a null id other than the fact that it's null because it has yet to be populated with a generated id. 00:41:15:ERROR org.hibernate.AssertionFailure (AssertionFailure.java:22) - an assertion failure occured (this may indicate a bug in Hibernate, but is more likely due to unsafe use of the session) org.hibernate.AssertionFailure: cannot copy a reference to an object with a null id at org.hibernate.type.EntityType.replace(EntityType.java:255) at org.hibernate.type.AbstractType.replace(AbstractType.java:153) at org.hibernate.type.TypeFactory.replaceAssociations(TypeFactory.java:564) at org.hibernate.event.def.DefaultMergeEventListener.copyValues(DefaultMergeEventListener.java:366) at org.hibernate.event.def.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:195) at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:123) at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:53) at org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:677) at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:661) at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:665) at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:228) at com.tmdworldwide.projectmanager.persist.BaseDao.save(BaseDao.java:37) at com.tmdworldwide.projectmanager.web.product.ProductActionBean.createProject(ProductActionBean.java:49) at com.tmdworldwide.projectmanager.web.product.CreateTrifoldBrochureActionBean.createProject(CreateTrifoldBrochureActionBean.java:60) 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 net.sourceforge.stripes.controller.DispatcherHelper$6.intercept(DispatcherHelper.java:442) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:158) at org.stripesstuff.plugin.security.SecurityInterceptor.interceptEventHandling(SecurityInterceptor.java:191) at org.stripesstuff.plugin.security.SecurityInterceptor.intercept(SecurityInterceptor.java:123) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.ExecutionContext.wrap(ExecutionContext.java:74) at net.sourceforge.stripes.controller.DispatcherHelper.invokeEventHandler(DispatcherHelper.java:440) at net.sourceforge.stripes.controller.DispatcherServlet.invokeEventHandler(DispatcherServlet.java:285) at net.sourceforge.stripes.controller.DispatcherServlet.doPost(DispatcherServlet.java:167) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at net.sourceforge.stripes.controller.StripesFilter.doFilter(StripesFilter.java:246) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:637) 00:41:15: WARN net.sourceforge.stripes.exception.DefaultExceptionHandler (Log.java:90) - Unhandled exception caught by the Stripes default exception handler. org.hibernate.AssertionFailure: cannot copy a reference to an object with a null id at org.hibernate.type.EntityType.replace(EntityType.java:255) at org.hibernate.type.AbstractType.replace(AbstractType.java:153) at org.hibernate.type.TypeFactory.replaceAssociations(TypeFactory.java:564) at org.hibernate.event.def.DefaultMergeEventListener.copyValues(DefaultMergeEventListener.java:366) at org.hibernate.event.def.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:195) at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:123) at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:53) at org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:677) at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:661) at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:665) at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:228) at com.tmdworldwide.projectmanager.persist.BaseDao.save(BaseDao.java:37) at com.tmdworldwide.projectmanager.web.product.ProductActionBean.createProject(ProductActionBean.java:49) at com.tmdworldwide.projectmanager.web.product.CreateTrifoldBrochureActionBean.createProject(CreateTrifoldBrochureActionBean.java:60) 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 net.sourceforge.stripes.controller.DispatcherHelper$6.intercept(DispatcherHelper.java:442) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:158) at org.stripesstuff.plugin.security.SecurityInterceptor.interceptEventHandling(SecurityInterceptor.java:191) at org.stripesstuff.plugin.security.SecurityInterceptor.intercept(SecurityInterceptor.java:123) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113) at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155) at net.sourceforge.stripes.controller.ExecutionContext.wrap(ExecutionContext.java:74) at net.sourceforge.stripes.controller.DispatcherHelper.invokeEventHandler(DispatcherHelper.java:440) at net.sourceforge.stripes.controller.DispatcherServlet.invokeEventHandler(DispatcherServlet.java:285) at net.sourceforge.stripes.controller.DispatcherServlet.doPost(DispatcherServlet.java:167) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at net.sourceforge.stripes.controller.StripesFilter.doFilter(StripesFilter.java:246) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:637)