Hibernate/JPA not possible to do eager loading

Question

Working with Spring MVC, Hibernate and JPA. I tried to Load some Collection from Controller and runned into an LazyLoading Exception. So i wanted to switch over to Egar loading.

I have two classes (Flightroute and Measurstations wich are in a Many to Many Realtion)

@Entity
@Table(name = "flightroutes")
public class Flightroute extends DomainObject<Integer> {

    @ManyToMany(fetch=FetchType.EAGER)
    private List<MeasureStation> measureStation;

---

@Entity
@Table(name = "measurestations")
public class MeasureStation extends DomainObject<Long> {
    @ManyToMany(mappedBy = "measureStation")
    private List<Flightroute> flightroutes;

But this seems not working, when the application start i run into following exception

Mai 03, 2013 5:58:08 PM org.apache.catalina.core.StandardContext listenerStart SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: atm] Unable to build EntityManagerFactory at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1488) 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$1.getObject(AbstractBeanFactory.java:295) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1117) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:922) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479) at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4791) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5285) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: javax.persistence.PersistenceException: [PersistenceUnit: atm] Unable to build EntityManagerFactory at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:930) at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:904) at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:92) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:288) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:310) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1547) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1485) ... 22 more Caused by: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags at org.hibernate.loader.BasicLoader.postInstantiate(BasicLoader.java:93) at org.hibernate.loader.entity.EntityLoader.(EntityLoader.java:118) at org.hibernate.loader.entity.EntityLoader.(EntityLoader.java:70) at org.hibernate.loader.entity.EntityLoader.(EntityLoader.java:53) at org.hibernate.loader.entity.BatchingEntityLoaderBuilder.buildLoader(BatchingEntityLoaderBuilder.java:75) at org.hibernate.persister.entity.AbstractEntityPersister.createEntityLoader(AbstractEntityPersister.java:2483) at org.hibernate.persister.entity.AbstractEntityPersister.createEntityLoader(AbstractEntityPersister.java:2496) at org.hibernate.persister.entity.AbstractEntityPersister.createLoaders(AbstractEntityPersister.java:3832) at org.hibernate.persister.entity.AbstractEntityPersister.postInstantiate(AbstractEntityPersister.java:3818) at org.hibernate.persister.entity.SingleTableEntityPersister.postInstantiate(SingleTableEntityPersister.java:1018) at org.hibernate.internal.SessionFactoryImpl.(SessionFactoryImpl.java:461) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1750) at org.hibernate.ejb.EntityManagerFactoryImpl.(EntityManagerFactoryImpl.java:94) at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:920) ... 28 more

I don't get it, can anyone hel me, and/or explain why this happend?

Answer 1

found out:

 @ManyToMany(fetch=FetchType.EAGER)
    private List<MeasureStation> measureStation;

hibernate wants to keep the ordering of elements within a list, ( with joins etc.) if there are two lists, hibernate cant keep the ordering.

Have a look