java Hibernate NullPointerException第二次合并

Question

合并对象时遇到问题，然后使用更多更新重新合并（在不同事务中）。获取以下堆栈跟踪：

Caused by: java.lang.NullPointerException at sun.reflect.GeneratedMethodAccessor63.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.hibernate.property.BasicPropertyAccessor$BasicGetter.get(BasicPropertyAccessor.java:169) at org.hibernate.tuple.component.AbstractComponentTuplizer.getPropertyValue(AbstractComponentTuplizer.java:76) at org.hibernate.type.ComponentType.getPropertyValue(ComponentType.java:414) at org.hibernate.type.ComponentType.getHashCode(ComponentType.java:255) at org.hibernate.engine.spi.CollectionKey.generateHashCode(CollectionKey.java:81) at org.hibernate.engine.spi.CollectionKey.<init>(CollectionKey.java:75) at org.hibernate.engine.spi.CollectionKey.<init>(CollectionKey.java:50) at org.hibernate.event.internal.AbstractFlushingEventListener.postFlush(AbstractFlushingEventListener.java:391) at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:57) at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1222) at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:425) at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101) at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:177) at org.hibernate.jpa.internal.TransactionImpl.commit(TransactionImpl.java:77) ... 149 more

我试图跟踪错误，并认为这可能与包含零项的OneToMany列表有关，但经过数小时的搜索，我没有发现有关此问题的任何信息

非常感谢您的帮助