初学Hibernate,让人抓狂
2011-07-27 23:09
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Hibernate是个强大,开发效率高的开源框架—这已是行业所公认的事实.
对于初接触Hibernate的我来说,却因为他强大的封装能力,出现问题时,完成不知从何处下手.
信手写了个Person类:package com.wls.domain; import java.util.Date; public class Person { private Integer personId; private String name; private Date birthday; private Address address; public Person(){ } public Integer getPersonId() { return personId; } public void setPersonId(Integer personId) { this.personId = personId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } @Override public String toString() { return "Person [personId=" + personId + ", name=" + name + ", birthday=" + birthday + ", address=" + address + "]"; } }
再写一个Address类:package com.wls.domain; import java.util.Date; public class Address { private Integer addressId; private String addressDetail; private Person person; public Address(){ } public Address(String addressDetail){ this.addressDetail=addressDetail; } public Integer getAddressId() { return addressId; } public void setAddressId(Integer addressId) { this.addressId = addressId; } public String getAddressDetail() { return addressDetail; } public void setAddressDetail(String addressDetail) { this.addressDetail = addressDetail; } public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } @Override public String toString() { return "Address [addressId=" + addressId + ", addressDetail=" + addressDetail +"]"; }}
这个两Pojo对应的映射文件为:<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.wls.domain"> <class name="Person"> <id name="personId" type="java.lang.Integer"> <generator class="native"></generator> </id> <property name="name" type="java.lang.String"></property> <property name="birthday" type="java.util.Date"></property> <one-to-one name="address" class="Address" property-ref="addressId" cascade="save-update" > </one-to-one> </class> <class name="Address"> <id name="addressId" type="java.lang.Integer"> <generator class="native"></generator> </id> <property name="addressDetail" type="java.lang.String"></property> <many-to-one name="person" class="Person" unique="true" not-null="true"></many-to-one> </class>
</hibernate-mapping>
前奏写好了,之后写了个DAO--UserManagerDao:package com.wls.dao; import java.util.ArrayList;import[/b] java.util.List; import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction; import com.wls.domain.Address;import com.wls.domain.Person; public class UserManagerDao { private SessionFactory sessionFactory; private Session session; public void setSessionFactory(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory; } public Session getSession() { if(session==null){ session=sessionFactory.openSession(); } return session; } public Integer addAddress(Address address){ Transaction tx=getSession().beginTransaction(); Integer AddressId=(Integer)getSession().save(address); tx.commit(); return AddressId; } public Integer addPerson(Person person){ Transaction tx=getSession().beginTransaction(); Integer personId=(Integer)getSession().save(person); tx.commit(); return personId; } public Person getPerson(Integer personId){ Transaction tx=getSession().beginTransaction(); Person person=(Person) getSession().get(Person.class, personId); tx.commit(); return person; } public List<Person> getAllPerons(){ Transaction tx=getSession().beginTransaction(); Query query=getSession().createQuery("select person from Person person"); if(query==null){ System.out.println("query is null"); return new ArrayList<Person>(); }else{ System.out.println("query is not null"); } List<Person> persons=query.list(); tx.commit(); return persons; } public List<Address> getAllAddresses(){ Transaction tx=getSession().beginTransaction(); Query query=getSession().createQuery("select person from Address person"); if(query==null){ System.out.println("query is null"); return new ArrayList<Address>(); }else{ System.out.println("query is not null"); } List<Address> addresses=query.list(); tx.commit(); return addresses; } }
最后,就只差用于测试的类了—MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); address.setPerson(person); userManagerDao.addAddress(address); System.out.println("Main Mehtod End!"); }}
随手点了下运行按钮,却出现了如下错误:Hibernate: select hibernate_sequence.nextval from dualException in thread "main" org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.wls.domain.Person at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:243) at org.hibernate.type.EntityType.getIdentifier(EntityType.java:456) at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:265) at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:275) at org.hibernate.type.TypeHelper.findDirty(TypeHelper.java:295) at org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:3403) at org.hibernate.event.def.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:520) at org.hibernate.event.def.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:230) at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:154) at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:219) at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:99) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133) at com.wls.dao.UserManagerDao.addAddress(UserManagerDao.java:33)
at com.wls.test.MainTest.main(MainTest.java:33)
再次确认映射文件,我已经写了cascade=save-update为什么会出现如此问题?
思考了半个小时,头疼,放弃了.
然后改了一下MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); Integer personId=userManagerDao.addPerson(person); address.setPerson(person); userManagerDao.addAddress(address); List<Address> addresses=userManagerDao.getAllAddresses(); for(Address a:addresses){ System.out.println(a); } System.out.println("Main Mehtod End!"); }}
运行结果如春风吹过,舒畅的感觉:Hibernate: select hibernate_sequence.nextval from dualHibernate: insert into Person (name, birthday, personId) values (?, ?, ?)Hibernate: select hibernate_sequence.nextval from dualHibernate: insert into Address (addressDetail, person, addressId) values (?, ?, ?)query is not nullHibernate: select address0_.addressId as addressId1_, address0_.addressDetail as addressD2_1_, address0_.person as person1_ from Address address0_Address [addressId=42, addressDetail=广东广州]Address [addressId=44, addressDetail=广东广州]Address [addressId=46, addressDetail=广东广州]Address [addressId=48, addressDetail=广东广州]Address [addressId=50, addressDetail=广东广州]Address [addressId=52, addressDetail=广东广州]Address [addressId=55, addressDetail=广东广州]Main Mehtod End!
再改MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); Integer personId=userManagerDao.addPerson(person); address.setPerson(person); userManagerDao.addAddress(address); List<Person> persons=userManagerDao.getAllPerons(); for(Person p:persons){ System.out.println(p); } System.out.println("Main Mehtod End!"); }}
想不到冬天来得这么快:Exception in thread "main" java.lang.NullPointerException at org.hibernate.persister.entity.AbstractEntityPersister.loadByUniqueKey(AbstractEntityPersister.java:1791) at org.hibernate.type.EntityType.loadByUniqueKey(EntityType.java:681) at org.hibernate.type.EntityType.resolve(EntityType.java:441) at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139) at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:982) at org.hibernate.loader.Loader.doQuery(Loader.java:857) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274) at org.hibernate.loader.Loader.doList(Loader.java:2533) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276) at org.hibernate.loader.Loader.list(Loader.java:2271) at org.hibernate.loader.hql.QueryLoader.list(
91ff
QueryLoader.java:452) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1268) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at com.wls.dao.UserManagerDao.getAllPerons(UserManagerDao.java:60) at com.wls.test.MainTest.main(MainTest.java:35)
想了半天,还是不明白为什么是java.lang.NullPointerException想经过测试, com.wls.dao.UserManagerDao.getAllPerons(UserManagerDao.java:60)中的query并不是null.看来问题是出在Peson对象上面了.
那是不是说我不用Address的话永远就取不了Peson了.
解决方案在哪里,又是仰望星空半天.
嗯,解决方案不在今天.
对于初接触Hibernate的我来说,却因为他强大的封装能力,出现问题时,完成不知从何处下手.
信手写了个Person类:package com.wls.domain; import java.util.Date; public class Person { private Integer personId; private String name; private Date birthday; private Address address; public Person(){ } public Integer getPersonId() { return personId; } public void setPersonId(Integer personId) { this.personId = personId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } @Override public String toString() { return "Person [personId=" + personId + ", name=" + name + ", birthday=" + birthday + ", address=" + address + "]"; } }
再写一个Address类:package com.wls.domain; import java.util.Date; public class Address { private Integer addressId; private String addressDetail; private Person person; public Address(){ } public Address(String addressDetail){ this.addressDetail=addressDetail; } public Integer getAddressId() { return addressId; } public void setAddressId(Integer addressId) { this.addressId = addressId; } public String getAddressDetail() { return addressDetail; } public void setAddressDetail(String addressDetail) { this.addressDetail = addressDetail; } public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } @Override public String toString() { return "Address [addressId=" + addressId + ", addressDetail=" + addressDetail +"]"; }}
这个两Pojo对应的映射文件为:<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.wls.domain"> <class name="Person"> <id name="personId" type="java.lang.Integer"> <generator class="native"></generator> </id> <property name="name" type="java.lang.String"></property> <property name="birthday" type="java.util.Date"></property> <one-to-one name="address" class="Address" property-ref="addressId" cascade="save-update" > </one-to-one> </class> <class name="Address"> <id name="addressId" type="java.lang.Integer"> <generator class="native"></generator> </id> <property name="addressDetail" type="java.lang.String"></property> <many-to-one name="person" class="Person" unique="true" not-null="true"></many-to-one> </class>
</hibernate-mapping>
前奏写好了,之后写了个DAO--UserManagerDao:package com.wls.dao; import java.util.ArrayList;import[/b] java.util.List; import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction; import com.wls.domain.Address;import com.wls.domain.Person; public class UserManagerDao { private SessionFactory sessionFactory; private Session session; public void setSessionFactory(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory; } public Session getSession() { if(session==null){ session=sessionFactory.openSession(); } return session; } public Integer addAddress(Address address){ Transaction tx=getSession().beginTransaction(); Integer AddressId=(Integer)getSession().save(address); tx.commit(); return AddressId; } public Integer addPerson(Person person){ Transaction tx=getSession().beginTransaction(); Integer personId=(Integer)getSession().save(person); tx.commit(); return personId; } public Person getPerson(Integer personId){ Transaction tx=getSession().beginTransaction(); Person person=(Person) getSession().get(Person.class, personId); tx.commit(); return person; } public List<Person> getAllPerons(){ Transaction tx=getSession().beginTransaction(); Query query=getSession().createQuery("select person from Person person"); if(query==null){ System.out.println("query is null"); return new ArrayList<Person>(); }else{ System.out.println("query is not null"); } List<Person> persons=query.list(); tx.commit(); return persons; } public List<Address> getAllAddresses(){ Transaction tx=getSession().beginTransaction(); Query query=getSession().createQuery("select person from Address person"); if(query==null){ System.out.println("query is null"); return new ArrayList<Address>(); }else{ System.out.println("query is not null"); } List<Address> addresses=query.list(); tx.commit(); return addresses; } }
最后,就只差用于测试的类了—MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); address.setPerson(person); userManagerDao.addAddress(address); System.out.println("Main Mehtod End!"); }}
随手点了下运行按钮,却出现了如下错误:Hibernate: select hibernate_sequence.nextval from dualException in thread "main" org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.wls.domain.Person at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:243) at org.hibernate.type.EntityType.getIdentifier(EntityType.java:456) at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:265) at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:275) at org.hibernate.type.TypeHelper.findDirty(TypeHelper.java:295) at org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:3403) at org.hibernate.event.def.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:520) at org.hibernate.event.def.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:230) at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:154) at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:219) at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:99) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133) at com.wls.dao.UserManagerDao.addAddress(UserManagerDao.java:33)
at com.wls.test.MainTest.main(MainTest.java:33)
再次确认映射文件,我已经写了cascade=save-update为什么会出现如此问题?
思考了半个小时,头疼,放弃了.
然后改了一下MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); Integer personId=userManagerDao.addPerson(person); address.setPerson(person); userManagerDao.addAddress(address); List<Address> addresses=userManagerDao.getAllAddresses(); for(Address a:addresses){ System.out.println(a); } System.out.println("Main Mehtod End!"); }}
运行结果如春风吹过,舒畅的感觉:Hibernate: select hibernate_sequence.nextval from dualHibernate: insert into Person (name, birthday, personId) values (?, ?, ?)Hibernate: select hibernate_sequence.nextval from dualHibernate: insert into Address (addressDetail, person, addressId) values (?, ?, ?)query is not nullHibernate: select address0_.addressId as addressId1_, address0_.addressDetail as addressD2_1_, address0_.person as person1_ from Address address0_Address [addressId=42, addressDetail=广东广州]Address [addressId=44, addressDetail=广东广州]Address [addressId=46, addressDetail=广东广州]Address [addressId=48, addressDetail=广东广州]Address [addressId=50, addressDetail=广东广州]Address [addressId=52, addressDetail=广东广州]Address [addressId=55, addressDetail=广东广州]Main Mehtod End!
再改MainTest:package com.wls.test; import java.util.Date;import java.util.List; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.wls.dao.UserManagerDao;import com.wls.domain.Address;import com.wls.domain.Person; public class MainTest { public static void main(String[] args){ System.out.println("Main Method!"); ApplicationContext context=new ClassPathXmlApplicationContext("SpringConfig.xml"); UserManagerDao userManagerDao=context.getBean("userManagerDao", UserManagerDao.class); Address address=new Address("广东广州"); Person person=new Person(); person.setBirthday(new Date()); person.setName("佢顺"); Integer personId=userManagerDao.addPerson(person); address.setPerson(person); userManagerDao.addAddress(address); List<Person> persons=userManagerDao.getAllPerons(); for(Person p:persons){ System.out.println(p); } System.out.println("Main Mehtod End!"); }}
想不到冬天来得这么快:Exception in thread "main" java.lang.NullPointerException at org.hibernate.persister.entity.AbstractEntityPersister.loadByUniqueKey(AbstractEntityPersister.java:1791) at org.hibernate.type.EntityType.loadByUniqueKey(EntityType.java:681) at org.hibernate.type.EntityType.resolve(EntityType.java:441) at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139) at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:982) at org.hibernate.loader.Loader.doQuery(Loader.java:857) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274) at org.hibernate.loader.Loader.doList(Loader.java:2533) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276) at org.hibernate.loader.Loader.list(Loader.java:2271) at org.hibernate.loader.hql.QueryLoader.list(
91ff
QueryLoader.java:452) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1268) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at com.wls.dao.UserManagerDao.getAllPerons(UserManagerDao.java:60) at com.wls.test.MainTest.main(MainTest.java:35)
想了半天,还是不明白为什么是java.lang.NullPointerException想经过测试, com.wls.dao.UserManagerDao.getAllPerons(UserManagerDao.java:60)中的query并不是null.看来问题是出在Peson对象上面了.
那是不是说我不用Address的话永远就取不了Peson了.
解决方案在哪里,又是仰望星空半天.
嗯,解决方案不在今天.
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