在我们的应用程序中,我想生成一份报告。因此 Foo
和关联的 Bar
实体的多个实例被加载(但未更改)。相关数据取自实体并存储在报告 bean 中以用于实际报告生成。当事务关闭并发生 Hibernate 刷新错误时(见下文)。
除了其他属性,Foo
还持有对Bar
的引用。这是两个类的摘录:
@Entity
@Table(name = "FOO")
public class Foo {
@Column(name = "BAR_ID")
private Long barId;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(insertable = false, updatable = false)
private Bar bar;
public Long getBarId() {
return barId;
}
public void setBarId(Long barId) {
this.barId = barId;
}
public Bar getBar() {
return bar;
}
// no setter for "bar"
// other attributes
}
@Entity
@Table(name = "BAR")
public class Bar {
@OneToMany(mappedBy = "bar", fetch = LAZY)
private List<Foo> foos;
// no getter/setter for "foos"
// other attributes
}
具有各种其他操作(包括创建、编辑、删除上述实体)的整个应用程序完美无缺,但在创建报告时出现奇怪的错误:
1)
org.springframework.orm.hibernate4.HibernateSystemException: Found two representations of same collection: Bar.foos; nested exception is org.hibernate.HibernateException: Found two representations of same collection: Bar.foos
at org.springframework.orm.hibernate4.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:216)
at org.springframework.orm.hibernate4.HibernateTransactionManager.convertHibernateAccessException(HibernateTransactionManager.java:681)
at org.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:563)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:757)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:726)
at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:478)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:272)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85)
at de.ba.wws.aop.TransactionTimeAspect.setTransactionTime(TransactionTimeAspect.java:20)
[...]
Caused by: org.hibernate.HibernateException: Found two representations of same collection: Bar.foos
at org.hibernate.engine.internal.Collections.processReachableCollection(Collections.java:170)
at org.hibernate.event.internal.FlushVisitor.processCollection(FlushVisitor.java:59)
at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:121)
at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:82)
at org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:76)
at org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:172)
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:231)
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:102)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:55)
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.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:555)
... 119 more
2)
java.lang.NullPointerException
at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:155)
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:91)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:55)
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.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:555)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:757)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:726)
at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:478)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:272)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85)
at de.ba.wws.aop.TransactionTimeAspect.setTransactionTime(TransactionTimeAspect.java:20)
[...]
3) org.hibernate.internal.util.compare.ComparableComparator.compare(Comparable, Comparable)
中的 NullPointerException
(两个参数 null
). (我无法为此提供堆栈跟踪,因为在撰写本文时我无法生成它。)
我在执行报告时遇到上述三个错误之一(或根本没有错误)。有时我需要多次调用报告才能产生错误,有时第一次运行就已经产生错误。我无法弄清楚是什么导致了这种行为。
我发现的唯一解决方法是将显示的both 属性的获取类型切换为EAGER
。然后一切正常,但由于预取的数据量很大,所以并不理想。
欢迎任何提示,如果您需要任何进一步的详细信息,请告诉我。
我们目前使用的是 Hibernate 4.3.8。我在本地尝试了较新的版本(4.3.11 显示了相同的问题),但是升级到 5.x 是一项主要任务,并且只有在有人可以向我们保证问题已解决(如果它实际上是 Hibernate)的情况下才能在短时间内完成问题)在 5.x 中。
最佳答案
好吧,我终于明白问题是什么了:
由于数据量巨大,报告生成需要花费大量时间,因此生成并行。在执行程序线程的处理部分中,一些对象从 bean
中引用——它们实际上仍然是 Hibernate
管理的实体——和 Hibernate
无法解析那些 proxies
(因为 session
在 threads
中无效)。
奇怪的是,当将 Hibernate
日志记录设置为 trace
时,这些问题(实际上是真正的异常!)才可见,并且由此产生的异常并不像底层的!
这也解释了为什么当获取模式设置为 EAGER
时报告生成工作正常。
我目前的解决方案是确保在实际多线程处理之前从实体(在 beans
中)获取所有需要的数据。
关于java - 带有 Hibernate 和获取类型 LAZY 的奇怪 NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55969440/