数据传输对象（dto）：Hibernate重复表映射

Question

我想在一个大清单中显示一些大型JPA（Hibernate）实体。为了获得合理的效果，并避免大量的＆＃39;加入，我想为我的实体创建一些DTO。

实体有一个超类，所以我使用＆＃34;表每个类继承映射＆＃34; ：

@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)

对于DTO，我使用了相同的JPA映射注释，排除了较大的字段。但这导致了一个例外：

org.hibernate.DuplicateMappingException: Duplicate table mapping

完整的堆栈跟踪：

java.lang.IllegalStateException: Failed to load ApplicationContext
    at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:91)
    at org.springframework.test.context.DefaultTestContext.getApplicationContext(DefaultTestContext.java:74)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:116)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:82)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:212)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:199)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:251)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:253)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:216)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:82)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:60)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:67)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:162)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
    at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
    at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class org.nuytsm.HibernateDtoDuplicateTableMapping.springconfig.SpringOrmConfig: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: PU] Unable to build Hibernate SessionFactory
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1568)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:540)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:229)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:956)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:747)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:125)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:108)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:260)
    at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:63)
    at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:83)
    ... 31 more
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: PU] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:1239)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.access$600(EntityManagerFactoryBuilderImpl.java:120)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:855)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:845)
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:398)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:844)
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:341)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:318)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1627)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1564)
    ... 46 more
Caused by: org.hibernate.DuplicateMappingException: Duplicate table mapping SubClass1
    at org.hibernate.cfg.Configuration$MappingsImpl.addDenormalizedTable(Configuration.java:2965)
    at org.hibernate.cfg.annotations.TableBinder.buildAndFillTable(TableBinder.java:289)
    at org.hibernate.cfg.annotations.TableBinder.buildAndFillTable(TableBinder.java:339)
    at org.hibernate.cfg.annotations.EntityBinder.bindTable(EntityBinder.java:594)
    at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:677)
    at org.hibernate.cfg.Configuration$MetadataSourceQueue.processAnnotatedClassesQueue(Configuration.java:3845)
    at org.hibernate.cfg.Configuration$MetadataSourceQueue.processMetadata(Configuration.java:3799)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1412)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1846)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:852)
    ... 54 more

所以是的，异常说明了我想要实现的目标： - ）。

实体：

超类：

    @Entity

    @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
    public class SuperClass {

        @Id
        @GeneratedValue(strategy = GenerationType.TABLE)
        @Column(name = "SID", nullable = false)
        private Long id;

        @Column(name = "NAME")
        private String name;

Subclass1：

@Entity
@Table(name = "SubClass1")
public class SubClass1 extends SuperClass{

    @Column(name="LONGSTRING")
    @Lob
    private String tooLongStringSoINeedDTO;

Subclass2：

@Entity
@Table(name = "SubClass2")
public class SubClass2 extends SuperClass{

    @Column(name="BYTEARRAY")
    @Lob
    private byte[] someBigArray;

SuperclassDTO：

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class SuperClassDto {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    @Column(name = "SID", nullable = false)
    private Long id;

    @Column(name = "NAME")
    private String name;

SubClass1DTO：

@Entity
@Table(name = "SubClass1")
public class SubClass1Dto extends SuperClassDto{

SubClass2DTO：

@Entity
@Table(name = "SubClass2")
public class SubClass2Dto extends SuperClassDto{

我煞费苦心地制作了一个最小的github maven project来说明这个问题，请随意尝试一下。您可以运行OrmTest junit测试来获取异常。

任何建议都会受到赞赏。 感谢

Answer 1

您对两个不同的类使用相同的表名。这就是例外情况。

DTO-s不是实体。删除这些注释。我假设sudo /etc/init.d/apache2 restart 也不是实体。 （你有一个名为SuperClassDTO的桌子吗？）

我认为你应该使用SUPER_CLASS_DTO作为基本实体，@MappedSuperclass作为子类。然后，DTO-s应该扩展超类，而不需要任何注释。

要了解差异，check this answer

修改

超类：

@Entity

Subclass1：

@MappedSuperclass
public class SuperClass {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    @Column(name = "SID", nullable = false)
    private Long id;

    @Column(name = "NAME")
    private String name;

Subclass2：

@Entity
@Table(name = "SubClass1")
public class SubClass1 extends SuperClass {

    @Column(name="LONGSTRING")
    @Lob
    private String tooLongStringSoINeedDTO;

SuperclassDTO：

将其删除

SubClass1DTO：

@Entity
@Table(name = "SubClass2")
public class SubClass2 extends SuperClass {

    @Column(name="BYTEARRAY")
    @Lob
    private byte[] someBigArray;

SubClass2DTO：

public class SubClass1Dto extends SuperClass {

Answer 2

这可以通过 @ Embedded ＆amp;来实现。 @ Embeddable 注释。

例如：

@Entity
public class Employee {
    @Embedded
    private EmployeeDetails details;
}

@Embeddable
public class EmployeeDetails {
}

您还可以在超类中创建一个仅包含必填字段的嵌入类。 因此消除了创建DTO的开销。

OR

如果您更喜欢使用 XML映射，那么

<!-- Hibernate Mapping 1 -->

<class name="com.SubClass1" table="SubClass1_Table">

<!-- Hibernate Mapping 2 -->

<class name="com.SubClass1" table="SubClass1_Table">