爲什麼hibernate在域updatable = false時執行isEqual

Question

我有一個blob字段，當我在表中的其他字段上進行保存時，不希望更新的blob字段。儘管我已經將字段指定爲updatable = false，但Hibernate似乎正在執行areEqual檢查。由於該字段是惰性加載，因此它爲空，並且在保存時執行areEqual檢查時，我得到一個ClassCastException。當它不可更新時，爲什麼它會在該字段上進行比較？

所以我的字段指定爲：

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

在org.springframework.data.repository.CrudRepository.save（）我收到以下錯誤：

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

可以使​​方法，這將是更新之前加載惰性加載字段

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