Spring Data Hibernate Cascade

Question

我在使用Spring Data时遇到了与hibernates级联操作有关的一些问题。 起初我的实体类：

@Entity
public class EntityOne {

    @Id
    private String code;

    @ManyToOne(optional = false, cascade = { CascadeType.REFRESH, CascadeType.MERGE, CascadeType.PERSIST })
    private EntityTwo entityTwo;

}


@Entity
public class EntityTwo {

    @Id
    private String code;


    @OneToMany(mappedBy = "entityTwo")
    private Set<EntityOne> entitiesOne;
}

我已经编写了一个基于Spring Batch的EntityImport，它使用了一个Processer，它通过Repository.findOne(example)检查是否已有现有实体（并进行一些深度属性合并）和RepositoryItemWriter来写“创建”实体进入数据库。

现在我的问题：如果数据库中没有现有的ParentData，一切正常。导入会创建一个EntityOne，其链接为EntityTwo。使用保存后，两个实体都保留在数据库中。 但是当我尝试重复这个过程时，我得到一个DataIntegrityViolationException

Caused by: javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [EntityTwo#EntityTwoCode]
        at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1735)
        at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
        at org.hibernate.jpa.internal.QueryImpl.getSingleResult(QueryImpl.java:524)
        at org.hibernate.jpa.criteria.compile.CriteriaQueryTypeQueryAdapter.getSingleResult(CriteriaQueryTypeQueryAdapter.java:71)
        at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findOne(SimpleJpaRepository.java:425)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:497)
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:503)
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:488)
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:460)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
        at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
        at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
        at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)

奇怪的是，我在Repository.save(EntityOne)调用时没有得到这个，但在Repository.findOne(example.of(EntityOne))调用之前，这导致了hibernate的自动刷新导致上面的异常。