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POHibernate/Spring: failed to lazily initialize - no session or session was closed
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For an answer scroll down to the end of this... The basic problem is the same as asked multiple time. I have a simple program with two POJOs Event and User - where a user can have multiple events. <pre><code>@Entity @Table public class Event { private Long id; private String name; private User user; @Column @Id @GeneratedValue public Long getId() {return id;} public void setId(Long id) { this.id = id; } @Column public String getName() {return name;} public void setName(String name) {this.name = name;} @ManyToOne @JoinColumn(name="user_id") public User getUser() {return user;} public void setUser(User user) {this.user = user;} } </code></pre> The User: <pre><code>@Entity @Table public class User { private Long id; private String name; private List<Event> events; @Column @Id @GeneratedValue public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column public String getName() { return name; } public void setName(String name) { this.name = name; } @OneToMany(mappedBy="user", fetch=FetchType.LAZY) public List<Event> getEvents() { return events; } public void setEvents(List<Event> events) { this.events = events; } } </code></pre> Note: This is a sample project. I really want to use Lazy fetching here. Now we need to configure spring and hibernate and have a simple basic-db.xml for loading: <pre> <code> <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd"> <bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" scope="thread"> <property name="driverClassName" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://192.168.1.34:3306/hibernateTest" /> <property name="username" value="root" /> <property name="password" value="" /> <aop:scoped-proxy/> </bean> <bean class="org.springframework.beans.factory.config.CustomScopeConfigurer"> <property name="scopes"> <map> <entry key="thread"> <bean class="org.springframework.context.support.SimpleThreadScope" /> </entry> </map> </property> </bean> <bean id="mySessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" scope="thread"> <property name="dataSource" ref="myDataSource" /> <property name="annotatedClasses"> <list> <value>data.model.User</value> <value>data.model.Event</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.hbm2ddl.auto">create</prop> </props> </property> <aop:scoped-proxy/> </bean> <bean id="myUserDAO" class="data.dao.impl.UserDaoImpl"> <property name="sessionFactory" ref="mySessionFactory" /> </bean> <bean id="myEventDAO" class="data.dao.impl.EventDaoImpl"> <property name="sessionFactory" ref="mySessionFactory" /> </bean> </beans> </code> </pre> Note: I played around with the CustomScopeConfigurer and SimpleThreadScope, but that didnt change anything. I have a simple dao-impl (only pasting the userDao - the EventDao is pretty much the same - except with out the "listWith" function: <pre> <code> public class UserDaoImpl implements UserDao{ private HibernateTemplate hibernateTemplate; public void setSessionFactory(SessionFactory sessionFactory) { this.hibernateTemplate = new HibernateTemplate(sessionFactory); } @SuppressWarnings("unchecked") @Override public List listUser() { return hibernateTemplate.find("from User"); } @Override public void saveUser(User user) { hibernateTemplate.saveOrUpdate(user); } @Override public List listUserWithEvent() { List users = hibernateTemplate.find("from User"); for (User user : users) { System.out.println("LIST : " + user.getName() + ":"); user.getEvents().size(); } return users; } } </code> </pre> I am getting the org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at the line with user.getEvents().size(); And last but not least here is the Test class I use: <pre> <code> public class HibernateTest { public static void main(String[] args) { ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("basic-db.xml"); UserDao udao = (UserDao) ac.getBean("myUserDAO"); EventDao edao = (EventDao) ac.getBean("myEventDAO"); System.out.println("New user..."); User user = new User(); user.setName("test"); Event event1 = new Event(); event1.setName("Birthday1"); event1.setUser(user); Event event2 = new Event(); event2.setName("Birthday2"); event2.setUser(user); udao.saveUser(user); edao.saveEvent(event1); edao.saveEvent(event2); List users = udao.listUserWithEvent(); System.out.println("Events for users"); for (User u : users) { System.out.println(u.getId() + ":" + u.getName() + " --"); for (Event e : u.getEvents()) { System.out.println("\t" + e.getId() + ":" + e.getName()); } } ((ConfigurableApplicationContext)ac).close(); } } </code> </pre> and here is the Exception: <pre> 1621 [main] ERROR org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44) Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44) </pre> Things tried but did not work: <ul> <li>assign a threadScope and using beanfactory (I used "request" or "thread" - no difference noticed):</li> </ul> <pre> // scope stuff Scope threadScope = new SimpleThreadScope(); ConfigurableListableBeanFactory beanFactory = ac.getBeanFactory(); beanFactory.registerScope("request", threadScope); ac.refresh(); ... </pre> <ul> <li>Setting up a transaction by getting the session object from the deo:</li> </ul> <pre> ... Transaction tx = ((UserDaoImpl)udao).getSession().beginTransaction(); tx.begin(); users = udao.listUserWithEvent(); ... </pre> <ul> <li>getting a transaction within the listUserWithEvent()</li> </ul> <pre> public List listUserWithEvent() { SessionFactory sf = hibernateTemplate.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); tx.begin(); List users = hibernateTemplate.find("from User"); for (User user : users) { System.out.println("LIST : " + user.getName() + ":"); user.getEvents().size(); } tx.commit(); return users; } </pre> I am really out of ideas by now. Also, using the listUser or listEvent just work fine. Step forward: Thanks to Thierry I got one step further (I think). I created the MyTransaction class and do my whole work in there, getting everything from spring. The new main looks like this: <pre> <code> public static void main(String[] args) { ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("basic-db.xml"); // getting dao UserDao udao = (UserDao) ac.getBean("myUserDAO"); EventDao edao = (EventDao) ac.getBean("myEventDAO"); // gettting transaction template TransactionTemplate transactionTemplate = (TransactionTemplate) ac.getBean("transactionTemplate"); MyTransaction mt = new MyTransaction(udao, edao); transactionTemplate.execute(mt); ((ConfigurableApplicationContext)ac).close(); } </code> </pre> Unfortunately now there is a null-pointer Exception @: user.getEvents().size(); (in the daoImpl). I know that it should not be null (neither from the output in the console nor from the db layout). Here is the console output for more information (I did a check for user.getEvent() == null and printed "EVENT is NULL"): <pre> New user... Hibernate: insert into User (name) values (?) Hibernate: insert into User (name) values (?) Hibernate: insert into Event (name, user_id) values (?, ?) Hibernate: insert into Event (name, user_id) values (?, ?) Hibernate: insert into Event (name, user_id) values (?, ?) List users: Hibernate: select user0_.id as id0_, user0_.name as name0_ from User user0_ 1:User1 2:User2 List events: Hibernate: select event0_.id as id1_, event0_.name as name1_, event0_.user_id as user3_1_ from Event event0_ 1:Birthday1 for 1:User1 2:Birthday2 for 1:User1 3:Wedding for 2:User2 Hibernate: select user0_.id as id0_, user0_.name as name0_ from User user0_ Events for users 1:User1 -- EVENT is NULL 2:User2 -- EVENT is NULL </pre> You can get the sample project from <a href="http://www.gargan.org/code/hibernate-test1.tgz" rel="nofollow noreferrer">http://www.gargan.org/code/hibernate-test1.tgz</a> (it's an eclipse/maven project) The solution (for console applications) There are actually two solutions for this problem - depending on your environment: For a console application you need a transaction template which captures the actutal db logic and takes care of the transaction: <pre> <code> public class UserGetTransaction implements TransactionCallback{ public List users; protected ApplicationContext context; public UserGetTransaction (ApplicationContext context) { this.context = context; } @Override public Boolean doInTransaction(TransactionStatus arg0) { UserDao udao = (UserDao) ac.getBean("myUserDAO"); users = udao.listUserWithEvent(); return null; } } </code> </pre> You can use this by calling: <pre> <code> TransactionTemplate transactionTemplate = (TransactionTemplate) context.getBean("transactionTemplate"); UserGetTransaction mt = new UserGetTransaction(context); transactionTemplate.execute(mt); </code> </pre> In order for this to work you need to define the template class for spring (ie. in your basic-db.xml): <pre><code><bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate"> <property name="transactionManager" ref="transactionManager"/> </bean> </code></pre> Another (possible) solution thanks andi <pre><code> PlatformTransactionManager transactionManager = (PlatformTransactionManager) applicationContext.getBean("transactionManager"); DefaultTransactionAttribute transactionAttribute = new DefaultTransactionAttribute(TransactionDefinition.PROPAGATION_REQUIRED); transactionAttribute.setIsolationLevel(TransactionDefinition.ISOLATION_SERIALIZABLE); TransactionStatus status = transactionManager.getTransaction(transactionAttribute); boolean success = false; try { new UserDataAccessCode().execute(); success = true; } finally { if (success) { transactionManager.commit(status); } else { transactionManager.rollback(status); } } </code></pre> The solution (for servlets) Servlets are not that big of a problem. When you have a servlet you can simply start and bind a transaction at the beginning of your function and unbind it again at the end: <pre><code>public void doGet(...) { SessionFactory sessionFactory = (SessionFactory) context.getBean("sessionFactory"); Session session = SessionFactoryUtils.getSession(sessionFactory, true); TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(session)); // Your code.... TransactionSynchronizationManager.unbindResource(sessionFactory); } </code></pre>
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<java><hibernate><spring><lazy-loading>
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Hibernate/Spring: failed to lazily initialize - no session or session was closed
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