错误原因
A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2]; nested exception is org.hibernate.NonUniqueObjectException: A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2]] with root cause
org.hibernate.NonUniqueObjectException: A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2]
大意可以理解成在hibernate的更新操作时发生了主键冲突；我这里是由于多对多的关系导致的。因为Privilege和Role之间我的更新是直接 new 多个Privilege然后赋值给Role的Set，这是最根本的原因。要知道hibernate在session中判别实体是通过该实体的主键唯一性判别的。我的错误dao层方法：
public void updateRole(Role role) {
getHibernateTemplate().update(role);
}
service层方法：
public void editRole(Role role, String[] privilege_ids) {
Set<Privilege>set=new HashSet<>();
for (String id : privilege_ids) {
Privilege privilege=new Privilege();
privilege.setPrivilege_id((long) Integer.parseInt(id));
set.add(privilege);
}
role.setPrivileges(set);
roleDao.updateRole(role);
如果犯了和我相同的错误的话可以尝试使用
getHibernateTemplate().merge(role);
如果是操纵session操作的话使用
session.merge(role);
下面是hibernate的merge方法的具体实现
@Override
public <T> T merge(final T entity) throws DataAccessException {
return executeWithNativeSession(new HibernateCallback<T>() {
@Override
@SuppressWarnings("unchecked")
public T doInHibernate(Session session) throws HibernateException {
checkWriteOperationAllowed(session);
return (T) session.merge(entity);
}
});
}
hibernate有关merge官方解释：
<T> T org.springframework.orm.hibernate5.HibernateTemplate.merge(T entity) throws DataAccessException
Copy the state of the given object onto the persistent objectwith the same identifier. Follows JSR-220 semantics.
Similar to saveOrUpdate, but never associates the givenobject with the current Hibernate Session. In case of a new entity,the state will be copied over as well.
Note that merge will not update the identifiersin the passed-in object graph (in contrast to TopLink)! Considerregistering Spring's IdTransferringMergeEventListener ifyou would like to have newly assigned ids transferred to the originalobject graph too.
参照某位大佬的解释：
session.merge()方法会首先发送一句select语句，去数据库端获取UserInfo持久化标识所对应的表记录；然后自动生成一个持久化状态的UserInfo实体，与脱管状态的UserInfo实体做比较是否有所改变；一旦发生了改变，才会发送update语句执行更新。而按执行顺序，若两句session.merge()方法针对同一个脱管状态的UserInfo实体，那其结果只会执行最后一个session.merge()方法所发出的update语句。即使执行了session.merge()方法，UserInfo实体依然是脱管状态，
错误日志
严重: Servlet.service() for servlet [my-one] in context with path [/myone-web] threw exception [Request processing failed; nested exception is org.springframework.dao.DuplicateKeyException: A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2]; nested exception is org.hibernate.NonUniqueObjectException: A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2]] with root cause org.hibernate.NonUniqueObjectException: A different object with the same identifier value was already associated with the session : [com.dabai.pojo.Privilege#2] at org.hibernate.engine.internal.StatefulPersistenceContext.checkUniqueness(StatefulPersistenceContext.java:648) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:284) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:227) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:92) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73) at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:648) at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:640) at org.hibernate.engine.spi.CascadingActions$5.cascade(CascadingActions.java:218) at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:398) at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:323) at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:162) at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:431) at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:363) at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:326) at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:162) at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:111) at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:150) at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:141) at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:74) at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:38) at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1282) at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:465) at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:2963) at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2339) at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:485) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:147) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$100(JdbcResourceLocalTransactionCoordinatorImpl.java:38) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:231) at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:65) at org.springframework.orm.hibernate5.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:581) at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761) at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730) at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:485) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:291) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208) at com.sun.proxy.$Proxy46.editRole(Unknown Source)