休眠/JPA2 重复记录

Question

我正在尝试为一个项目学习 JPA 2 的基础知识，使用 Hibernate。我不确定的一件事是如何正确执行复合键。出于某种原因，当我简单地打印出表格的值时，我得到了两次。

表格本身是：

表格：Anim_Type

CrashNumber RecordNumber AnimalType
1000        1            2
1000        1            10

在我的主课中，我在它（Crash）和 AnimalTypes 之间有一个@OneToMany 关系：

@OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL)
@JoinColumn(name = "CRASH_NUMBER")
public List<AnimalType> getAnimalTypes() {
    return animalTypes;
}

AnimalType @Entity 应该具有所有 3 列的主键。这是 AnimalType 类：

@Entity
@Table(name = "ANIM_TYPE")
public class AnimalType {

private AnimalTypePK pk;

@EmbeddedId
@AttributeOverrides( {
    @AttributeOverride(name = "crashNum", column = @Column(name = "CRASH_NUMBER")),
    @AttributeOverride(name = "recordNum", column = @Column(name = "RECORD_NUMBER")),
    @AttributeOverride(name = "animalType", column = @Column(name = "ANIMAL_TYPE"))
})
public AnimalTypePK getPk() {
    return pk;
}

public void setPk(AnimalTypePK pk) {
    this.pk = pk;
}

public void print() {
    System.out.println("AnimalType: " + pk.getCrashNum() + " " + pk.getRecordNum() + " " + pk.getAnimalType());
}


}

我的 AnimalTypePK 类是：

@Embeddable
public class AnimalTypePK implements Serializable {

private static final long serialVersionUID = 1L;
private int crashNum;
private int recordNum;
private int animalType;

// getters and setters, plus hashCode() and equals(Object).
// no other JPA annotations in this class

}

当我使用上面的代码时，一切正常，但是当我打印 AnimalTypes 时，表中的 2 行重复：

动物种类

AnimalType: 1000 1 10
AnimalType: 1000 1 2
AnimalType: 1000 1 10
AnimalType: 1000 1 2

我不明白为什么？

谁能帮忙？

其次，我使用 AnimalType 中的 @AttributeOverrides 注解来告诉 Hibernate 列名。这是正确的方法吗？

谢谢！

克里斯

编辑： 我之前确实看到了标记的帖子，并按照接受的答案的方法，并将@Column 放入AnimalTypePK（取出AnimalType 中的@AttributeOverrides）。 但是当我尝试它时，我得到了一个例外：

Exception in thread "main"      org.springframework.dao.InvalidDataAccessResourceUsageException: could not extract ResultSet; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:242)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:225)
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:417)
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:131)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy34.findOne(Unknown Source)
at com.dbprototype.services.CrashService.readCrash(CrashService.java:28)
at com.dbprototype.services.CrashService$$FastClassBySpringCGLIB$$473ea387.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:718)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:654)
at com.dbprototype.services.CrashService$$EnhancerBySpringCGLIB$$a311f3d6.readCrash(<generated>)
at com.dbprototype.main.DBTest.main(DBTest.java:20)
Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:109)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:95)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:79)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.getResultSet(AbstractLoadPlanBasedLoader.java:434)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:186)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:121)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:86)
at org.hibernate.loader.entity.plan.AbstractLoadPlanBasedEntityLoader.load(AbstractLoadPlanBasedEntityLoader.java:167)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3955)
at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:508)
at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:478)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:219)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:278)
at org.hibernate.event.internal.DefaultLoadEventListener.doOnLoad(DefaultLoadEventListener.java:121)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:89)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1129)
at org.hibernate.internal.SessionImpl.access$2600(SessionImpl.java:164)
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2696)
at org.hibernate.internal.SessionImpl.get(SessionImpl.java:975)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:1075)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:1039)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:293)
at com.sun.proxy.$Proxy29.find(Unknown Source)
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findOne(SimpleJpaRepository.java:235)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:483)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:468)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:440)
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)
... 19 more
Caused by: java.sql.SQLSyntaxErrorException: ORA-00904: "ANIMALTYPE1_"."RECORDNUM": invalid identifier

at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:450)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:399)
at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:1017)
at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:655)
at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:249)
at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:566)
at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:215)
at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:58)
at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:776)
at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:897)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1034)
at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3820)
at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3867)
at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeQuery(OraclePreparedStatementWrapper.java:1502)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:70)
... 59 more

Answer 1

该问题与您在协会中使用 EAGER 的事实无关。

您可以在此处找到进一步的讨论。

https://howtoprogramwithjava.com/how-to-fix-duplicate-data-from-hibernate-queries/

Hibernate Criteria returns children multiple times with FetchType.EAGER

然后可能的修复是删除 Eager Fetch 或使用 Set 而不是 List 映射此关联。

关于您关于为什么使用 SET 已修复它的后续问题....

好吧，如果我们考虑以下几点：

持久化上下文的主要作用是确保一个 数据库实体对象由不超过一个内存中表示 同一 EntityManager 中的实体对象。每个 EntityManager 管理自己的持久性上下文。因此，数据库对象可以 由不同的内存实体对象表示 EntityManager 实例。 但检索相同的数据库对象更多 不止一次使用相同的 EntityManager 应该总是导致 相同的内存中实体对象。

http://www.objectdb.com/java/jpa/persistence/managed

鉴于上述陈述，如果我们考虑您原来的重复列表：

• 动物类型：1000 1 10
• 动物类型：1000 1 2
• 动物类型：1000 1 10
• 动物类型：1000 1 2

我们期望（假设 AnimalType 具有默认的 equals 方法或正确实现的自定义 equals 方法）

list.get(0).equals(list.get(2)) == true 

和

list.get(1).equals(list.get(3)) == true

当然，由于 Set 不能包含重复项，因此作为使用 Set 的副作用，重复记录会被过滤掉。

https://docs.oracle.com/javase/7/docs/api/java/util/Set.html

不包含重复元素的集合。更正式地说，集合 不包含元素对 e1 和 e2 使得 e1.equals(e2)...