尝试持久化和具有主键唯一约束的实体时出错

Posted 2023-04-18

【中文标题】尝试持久化和具有主键唯一约束的实体时出错

【英文标题】：Error while trying to persist and entity with unique constraint for primary key

【发布时间】：2013-11-12 04:46:18

【问题描述】：

我正在使用休眠和内存数据库 (hsqldb) 来保存数据。基本上我正在为该层编写Junit。 我在使用指定为@Id 的列的唯一属性时收到错误（用户缺少权限或找不到对象：CITY）。我想确保 cityId 和 cityName 都是唯一的。

@Entity
@Table(name="CITY")
public class City 
@Id
@GeneratedValue
@Column(name="CITY_ID",unique= true)
private long id;
@Column(name="CITY_NAME", nullable=false, unique= true)
private String name;

PFB 错误信息

org.hibernate.exception.SQLGrammarException: could not insert: [model.City]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2836)
    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
    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:705)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689)
    at com.loiane.dao.CityDAO.saveCity(CityDAO.java:39)
    at com.loiane.main.Main.main(Main.java:18)
Caused by: java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: CITY
    at org.hsqldb.jdbc.JDBCUtil.sqlException(Unknown Source)
    at org.hsqldb.jdbc.JDBCUtil.sqlException(Unknown Source)
    at org.hsqldb.jdbc.JDBCPreparedStatement.<init>(Unknown Source)
    at org.hsqldb.jdbc.JDBCConnection.prepareStatement(Unknown Source)
    at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:524)
    at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:116)
    at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.prepare(IdentityGenerator.java:90)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:54)
    ... 17 more

当我删除 cityId 的 unique 属性（@ Column）时，值会正确保留。

请让我知道您的 cmets 或任何相关链接，以帮助我了解其背后的原因。

【参考方案1】：

当您在 Hibernate 中将列声明为 @Id 时，它已被假定为唯一的。所以根据我的说法，你不需要唯一属性。

你可以看看Hibernate Docs

此外，由于您使用的是@GeneratedValue，请确保您已正确处理密钥的创建

如果你想将它设置为自动，你可以这样做

@GeneratedValue(strategy = GenerationType.AUTO)

如果你有一个想要使用的数据库序列，那么你可以这样设置它

@Entity
// Define a sequence - might also be in another class:
@SequenceGenerator(name="seq", initialValue=1, allocationSize=100)
public class EntityWithSequenceId 
// Use the sequence that is defined above:
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="seq")
@Id long id;

请参考以下link