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我有一個袋鼠腳本行是這樣的:爲什麼需要關係表從實體到同一實體
字段設置--class會員--fieldName invitedby --type會員--cardinality ONE_TO_MANY
Hibernate的要求與列成員和invitedby一個名爲member_invitedby表:
PersistenceException: [PersistenceUnit: megaadmin] Unable to build EntityManagerFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1486)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:524)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1117)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:922)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:383)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:283)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4791)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5285)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: megaadmin] Unable to build EntityManagerFactory
at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:915)
at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890)
at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:74)
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:286)
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:310)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1545)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1483)
... 22 more
Caused by: org.hibernate.HibernateException: Missing table: member_invitedby
at org.hibernate.cfg.Configuration.validateSchema(Configuration.java:1272)
at org.hibernate.tool.hbm2ddl.SchemaValidator.validate(SchemaValidator.java:155)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:506)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1750)
at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94)
at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905)
... 28 more
如果我manualy創建一個列成員和invitedby表member_invitedby此異常消失。
我不知道爲什麼hibernate需要一個n-m表,因爲一個成員只能由一個成員邀請,它是一個1-n!
問候。
沿着我的個人概念:很少有人認爲自我1-n不是實體s.o的存在的一部分。污染兒童s.o.它是一個反模式。嘿,你可以請一個具體的例子來解釋一下當一個孩子污染了嗎? – 2013-02-25 06:44:59
假設你有一個用戶和一個地址。用戶有多個地址。但辦事處也有地址。公司也有地址。和聯繫人也有地址。地址不需要知道它們是否適用於用戶,辦公室,公司或聯繫人。所以協會在任何情況下都是單向的一對多協會。您不希望地址表中有4個外鍵來執行此操作。如果您將一個提供程序添加到具有地址的一組實體中,則不希望在地址表中添加另一個可爲空的外鍵。在這種情況下,連接表是更好的選擇。 – 2013-02-25 08:10:41
續:至少這是JPA規範認爲的,因此他們決定在單向一對多關聯的情況下將其設置爲默認值。但是,如果您更喜歡使用joi列映射關聯,則他們可以通過將JoinColumn註釋添加到關聯來讓您做出其他選擇。如果關聯是雙向的,則默認是使用連接列。 – 2013-02-25 08:12:40