我们创建一个这样的EntityManagerFactory：
<bean id="dataSource"
class="org.apache.commons.dbcp2.BasicDataSource"
destroy-method="close"
p:driverClassName="${jdbc.driver}"
p:url="${jdbc.url}"
p:username="${jdbc.username}"
p:password="${jdbc.password}"
p:initialSize="${dbcp.initialSize}"
p:maxTotal="${dbcp.maxActive}"
p:maxIdle="${dbcp.maxIdle}"
p:minIdle="${dbcp.minIdle}"
p:maxWaitMillis="${dbcp.maxWait}"
p:validationQuery="${dbcp.validationQuery}"/>
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
p:dataSource-ref="dataSource">
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
</property>
<property name="jpaProperties">
<props>
<prop key="hibernate.dialect">${hibernate.dialect}</prop>
<prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop>
<prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
<prop key="hibernate.generate_statistics">${hibernate.generate_statistics}</prop>
</props>
</property>
</bean>
<bean id="transactionManager"
class="org.springframework.orm.jpa.JpaTransactionManager"
p:entityManagerFactory-ref="entityManagerFactory"
p:dataSource-ref="dataSource"/>
这在Hibernate 4中按预期工作。我升级到Hibernate 5.1.0并开始获得此异常：
更新：这不是Hibernate 5特有的问题。这实际上只是从hiberate 4.2.5.Final升级到4.3.5.Final
WARN; May 22, 2016 9:7:34 PM; tid:17; | XmlWebApplicationContext refresh; Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationEx
ception: Error creating bean with name 'entityManagerFactory' defined in class path resource [fp-core-context.xml]: Invocation of init method failed; nested exception is javax.persistence.Persiste
nceException: [PersistenceUnit: fp] Unable to build Hibernate SessionFactory
ERROR; May 22, 2016 9:7:34 PM; tid:17; | ContextLoader initWebApplicationContext; Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [freedompop-core-context.xml]: Invocation of init method failed
; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: freedompop] Unable to build Hibernate SessionFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1578) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1054) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:829) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4811) [catalina.jar:8.0.33]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5251) [catalina.jar:8.0.33]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147) [catalina.jar:8.0.33]
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725) [catalina.jar:8.0.33]
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701) [catalina.jar:8.0.33]
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717) [catalina.jar:8.0.33]
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:587) [catalina.jar:8.0.33]
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1798) [catalina.jar:8.0.33]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_92]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_92]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_92]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_92]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_92]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: freedompop] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:884) ~[hibernate-entitymanager-5.1.0.Final.jar:5.1.0.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:343) ~[spring-orm-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:319) ~[spring-orm-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1637) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
... 25 common frames omitted
Caused by: java.lang.NullPointerException: null
at org.hibernate.loader.plan.build.internal.AbstractLoadPlanBuildingAssociationVisitationStrategy.foundCircularAssociation(AbstractLoadPlanBuildingAssociationVisitationStrategy.java:672) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitAttributeDefinition(MetamodelGraphWalker.java:146) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitAttributes(MetamodelGraphWalker.java:131) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitCompositeDefinition(MetamodelGraphWalker.java:199) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitCollectionIndex(MetamodelGraphWalker.java:230) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitCollectionDefinition(MetamodelGraphWalker.java:207) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.walking.spi.MetamodelGraphWalker.visitCollection(MetamodelGraphWalker.java:72) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.plan.build.spi.MetamodelDrivenLoadPlanBuilder.buildRootCollectionLoadPlan(MetamodelDrivenLoadPlanBuilder.java:54) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.<init>(AbstractLoadPlanBasedCollectionInitializer.java:62) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.collection.plan.CollectionLoader.<init>(CollectionLoader.java:94) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.collection.plan.CollectionLoader$Builder.byKey(CollectionLoader.java:87) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.collection.plan.AbstractBatchingCollectionInitializerBuilder.buildNonBatchingLoader(AbstractBatchingCollectionInitializerBuilder.java:28) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.loader.collection.BatchingCollectionInitializerBuilder.createBatchingOneToManyInitializer(BatchingCollectionInitializerBuilder.java:85) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.collection.OneToManyPersister.createCollectionInitializer(OneToManyPersister.java:497) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.persister.collection.AbstractCollectionPersister.postInstantiate(AbstractCollectionPersister.java:658) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:446) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:465) ~[hibernate-core-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:881) ~[hibernate-entitymanager-5.1.0.Final.jar:5.1.0.Final]
... 30 common frames omitted
Update2：这是评论中要求的persistence.xml：
<?xml version="1.0"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="companyName" transaction-type="RESOURCE_LOCAL"/>
</persistence>
问题显然是空指针异常，但什么是null？该错误没有提供导致空指针异常的详细信息。任何有关正在发生的事情的想法都将不胜感激。