Hibernate 常见错误

[main] ERROR org.hibernate.LazyInitializationException - could not initialize proxy - no Sessionorg.hibernate.LazyInitializationException : could not initialize proxy - no Session       at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:132)       at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174)       at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)       at cn.codemonkey.usermanagement.domain.Department_$$_javassist_2.getName(Department_$$_javassist_2.java)       at cn.codemonkey.usermanagement.ui.test.Base.main( Base.java:114)

无法初始化代理 - 没有会话

情景描述

使用HibernateUtil.selectObject(Employee.class, conditions)查询Employee对象完成后方法退出、会话关闭，使用employee.getDepartment().getName()查询Department对象属性时报错。

解决方法

将查询Employee对象和查询Department对象的语句放在同一会话中。

Exception in thread "main" org.hibernate.PropertyValueException : not-null property references a null or transient value: cn.codemonkey.usermanagement.domain.Employee.department       at org.hibernate.engine.Nullability.checkNullability( Nullability.java:95)       at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:313)       at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)       at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)       at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)       at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)       at org.hibernate.impl.SessionImpl.fireSave( SessionImpl.java:563)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:551)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:547)       at cn.codemonkey.usermanagement.hibernate.HibernateUtil.insertObject(HibernateUtil.java:200)       at cn.codemonkey.usermanagement.ui.test.Base.main( Base.java:110)

非空属性引用空值或暂态值

情景描述

<class name="Employee" table="T_Employee"><id name="id" column="eId"><generator class="native" /></id><property name="name" column="employeeName" /><many-to-one name="department" column="dId" not-null="true" /></class>

1) Not-null property references a null value

使用HibernateUtil.insertObject(employee)插入Employee对象之前没有为department字段赋值，department字段有非空约束，插入Employee对象时报错。

2) Not-null property references a transient value

使用HibernateUtil.insertObject(employee)插入Employee对象之前已经为department字段赋值，插入Employee对象之后插入Department对象，department字段有非空约束，插入Employee对象时报错。

解决方法

依赖字段赋值，使用HibernateUtil.insertObject(employee)插入Employee对象之前为department字段赋值；调整插入顺序，插入Employee对象之前插入Department对象。

[main] ERROR org.hibernate.event.def.AbstractFlushingEventListener - Could not synchronize database state with sessionorg.hibernate.TransientObjectException : object references an unsaved transient instance - save the transient instance before flushing: cn.codemonkey.usermanagement.domain.Employee       at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:242)       at org.hibernate.type.EntityType.getIdentifier( EntityType.java:430)       at org.hibernate.type.ManyToOneType.nullSafeSet( ManyToOneType.java:101)       at org.hibernate.persister.collection.AbstractCollectionPersister.writeElement(AbstractCollectionPersister.java:777)       at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1165)       at org.hibernate.action.CollectionRecreateAction.execute(CollectionRecreateAction.java:58)       at org.hibernate.engine.ActionQueue.execute( ActionQueue.java:279)       at org.hibernate.engine.ActionQueue.executeActions( ActionQueue.java:263)       at org.hibernate.engine.ActionQueue.executeActions( ActionQueue.java:171)       at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)       at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50)       at org.hibernate.impl.SessionImpl.flush( SessionImpl.java:1028)       at org.hibernate.impl.SessionImpl.managedFlush( SessionImpl.java:366)       at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:137)       at cn.codemonkey.usermanagement.hibernate.HibernateUtil.insertObject(HibernateUtil.java:201)       at cn.codemonkey.usermanagement.ui.test.Base.main( Base.java:118)

无法同步数据库和会话状态

对象引用未保存的暂态实例 - 清空前保存暂态实例

情景描述

<class name="Department" table="T_Department"><id name="id" column="dId"><generator class="native" /></id><property name="name" column="departName" /><set name="employees"><key column="dId"></key><one-to-many class="Employee" /></set></class>

使用HibernateUtil.insertObject(department)插入Department对象之前已经为employees字段赋值，插入Department对象之后插入Employee对象，插入Department对象时报错。

解决方法

依赖字段赋值，使用HibernateUtil.insertObject(department)插入Department对象之前为employees字段赋值；调整插入顺序，插入Department对象之前插入Employee对象。

Exception in thread "main" org.hibernate.MappingException: Unknown entity: cn.codemonkey.usermanagement.domain.IdCard       at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:628)       at org.hibernate.impl.SessionImpl.getEntityPersister( SessionImpl.java:1366)       at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:121)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)       at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)       at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)       at org.hibernate.impl.SessionImpl.fireSave( SessionImpl.java:563)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:551)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:547)       at cn.codemonkey.usermanagement.hibernate.HibernateUtil.insertObject(HibernateUtil.java:200)       at cn.codemonkey.usermanagement.ui.test.Base.main( Base.java:143)

未知实体 - cn.codemonkey.usermanagement.domain.IdCard

情景描述

使用HibernateUtil操作IdCard对象之前没有在Hibernate配置文件中引入对象映射文件，操作IdCard对象时报错。

解决方法

引入映射文件，使用HibernateUtil操作IdCard对象之前在Hibernate配置文件中引入对象映射文件。

<mapping resource="cn/codemonkey/usermanagement/domain/Person-IdCard.hbm.xml"/>

Exception in thread "main" org.hibernate.id.IdentifierGenerationException : attempted to assign id from null one-to-one property: person       at org.hibernate.id.ForeignGenerator.generate( ForeignGenerator.java:68)       at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:122)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)       at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)       at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)       at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)       at org.hibernate.impl.SessionImpl.fireSave( SessionImpl.java:563)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:551)       at org.hibernate.impl.SessionImpl.save( SessionImpl.java:547)       at cn.codemonkey.usermanagement.hibernate.HibernateUtil.insertObject(HibernateUtil.java:200)       at cn.codemonkey.usermanagement.ui.test.Base.main( Base.java:144)

尝试使用空值一对一属性为id赋值

情景描述

使用HibernateUtil.insertObject(idCard)插入IdCard对象之前没有为person字段赋值，插入IdCard对象时报错。

解决方法

为从对象的依赖字段赋值，使用HibernateUtil.insertObject(idCard)插入IdCard对象之前为person字段赋值。