双向OneToOne映射：从实体到子类，从超类到实体？

Question

我正在尝试在hibernate中建立一个棘手的双向OneToOne映射。我得到了以下课程：

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Parent {
     @OneToOne
     private AnotherEntity anotherEntity;
}
@Entity
public class Child1 extends Parent{}

@Entity
public class Child2 extends Parent{}

@Entity
public class AnotherEntity {

    @OneToOne(mappedBy = "anotherEntity")
    private Child1 child1;
    @OneToOne(mappedBy = "anotherEntity")
    private Child2 child2;
}

这里的问题是当我启动应用程序时：我收到以下消息：

org.hibernate.MappingException: property [anotherEntity] not found on entity [Child1]
    at org.hibernate.mapping.PersistentClass.getRecursiveProperty(PersistentClass.java:429)
    at org.hibernate.mapping.PersistentClass.getReferencedProperty(PersistentClass.java:369)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1614)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1362)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1727)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1778)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBuilder.buildSessionFactory(LocalSessionFactoryBuilder.java:189)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:350)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBean.afterPropertiesSet(LocalSessionFactoryBean.java:335)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1514)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1452)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:567)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:631)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:588)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:645)
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:508)
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:449)
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:133)
    at javax.servlet.GenericServlet.init(GenericServlet.java:160)
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1266)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1185)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1080)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5015)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5302)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:895)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:871)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:615)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:962)
    at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:536)
    at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1471)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:836)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:761)
    at org.apache.catalina.manager.ManagerServlet.check(ManagerServlet.java:1436)
    at org.apache.catalina.manager.ManagerServlet.deploy(ManagerServlet.java:673)
    at org.apache.catalina.manager.ManagerServlet.doPut(ManagerServlet.java:431)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:644)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:581)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)

一个明显的解决方案是将anotherEntity字段移至Child1和Child2，但这意味着会丢失从Parent到AnotherEntity的链接。

欢迎任何帮助。

Answer 1

简短的回答是你不能（使用Hibernate）。

首先，通过给出的示例，您要完成的是什么并不完全清楚。您已指定希望AnotherEntity具有类型Child1的两个属性。我猜你实际上想要其中一个，Child1和Child2。此外，您在两个属性上使用相同的mappedBy = "anotherEntity"，您是否真的想要在Parent上对anotherEntity进行两次引用？在任何一种情况下，这都有助于说明这种情况的问题：

您已指定InheritanceType.JOINED，这意味着Parent的外键 - ＆gt; AnotherEntity生活在Parent类映射到的任何表上。在这种情况下，Hibernate无法区分您的两个子类型，它必须完全依赖于Java类中指定的类型 - 这肯定会导致问题。

显然，其他JPA提供商可能会支持这种行为（但你可以看到为什么Hibernate选择不这样做，为什么你需要小心它）。有关参考，请参阅this类似的SO问题以及有关Hibernate论坛/ JIRA的各种讨论：

• [ANN-558] @OneToMany(mappedBy="") can not recognize properties in parent classes
• [HHH-4233] cant bind a child using mappedby relating to a parent attribute(polymorphism)
• Hibernate complains about missing property?