为什么Hibernate在字段上 updatable=false 时确实是相等的

Question

我有一个blob字段，当我保存表中的其他字段时，它不希望被更新。尽管我已经将该字段指定为updatable=false，Hibernate似乎正在进行areEqual检查。因为该字段是延迟加载的，所以它是null，当它在保存时进行areEqual检查时，我得到了一个ClassCastException。当它不可更新时，为什么要在那个字段上进行比较？

因此，我的字段被指定为：

@Basic(fetch = FetchType.LAZY)
@Column(
    insertable = true,
    updatable = false,
    name = "documentData"
)
@Lob private Blob documentData;

在org.springframework.data.repository.CrudRepository.save（）上，我得到以下错误：

java.lang.ClassCastException: org.hibernate.bytecode.instrumentation.spi.LazyPropertyInitializer$1 cannot be cast to java.sql.Blob
    at org.hibernate.type.descriptor.java.BlobTypeDescriptor.areEqual(BlobTypeDescriptor.java:45)
    at org.hibernate.type.AbstractStandardBasicType.isEqual(AbstractStandardBasicType.java:196)
    at org.hibernate.ejb.event.EJB3FlushEntityEventListener.copyState(EJB3FlushEntityEventListener.java:79)
    at org.hibernate.ejb.event.EJB3FlushEntityEventListener.invokeInterceptor(EJB3FlushEntityEventListener.java:66)
    at org.hibernate.event.internal.DefaultFlushEntityEventListener.handleInterception(DefaultFlushEntityEventListener.java:334)
    at org.hibernate.event.internal.DefaultFlushEntityEventListener.scheduleUpdate(DefaultFlushEntityEventListener.java:285)
    at org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:164)
    at org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:225)
    at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:99)
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1214)
    at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:403)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175)
    at org.hibernate.ejb.TransactionImpl.commit(TransactionImpl.java:75)
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:512)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:754)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:723)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:394)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:120)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:155)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.data.jpa.repository.support.LockModeRepositoryPostProcessor$LockModePopulatingMethodIntercceptor.invoke(LockModeRepositoryPostProcessor.java:91)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    at $Proxy216.save(Unknown Source)

Answer 1

您可以使@PreUpdate方法，即在更新之前加载延迟加载字段

  @PreUpdate
  private void loadField()
  {
     getDocumentData();  
  }