Spring Hibernate Transaction No Session Lazy Loading - spring

Question

I have a problem with only one controller that has a lazy loaded entity(there is a transaction initiated and commited, see stack trace)
17:56:46,084 DEBUG HibernateTransactionManager:438 - Found thread-bound Session [org.hibernate.impl.SessionImpl#6b204e88] for Hibernate transaction
17:56:46,085 DEBUG HibernateTransactionManager:471 - Participating in existing transaction
17:56:46,085 DEBUG HibernateTransactionManager:438 - Found thread-bound Session [org.hibernate.impl.SessionImpl#6b204e88] for Hibernate transaction
17:56:46,085 DEBUG HibernateTransactionManager:471 - Participating in existing transaction
Hibernate: select preference0_.id as id66_, preference0_.name as name66_, preference0_.value as value66_, preference0_.default_value as default4_66_, preference0_.updated_at as updated5_66_ from preferences preference0_ where preference0_.name='scheduleInterval'
17:56:46,086 DEBUG GooGooStatementCache:457 - cxnStmtMgr.statementSet( com.mysql.jdbc.JDBC4Connection#5ec60ee2 ).size(): 21
17:56:46,086 DEBUG GooGooStatementCache:196 - checkoutStatement: com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 111; checked out: 1; num connections: 10; num keys: 111
17:56:46,087 DEBUG GooGooStatementCache:271 - checkinStatement(): com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 111; checked out: 0; num connections: 10; num keys: 111
17:56:46,089 FATAL app:79 - service
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:167)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:215)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
at com.model.User_$$_javassist_76.getName(User_$$_javassist_76.java)
at com.model.json.ScheduleItemWrapper.wrap(ScheduleItemWrapper.java:55)
at com.web.controllers.ajax.Model.wrap(Model.java:127)
at com.web.controllers.ajax.Model.toJSON(Model.java:165)
at com.web.controllers.ajax.Model.getContent(Model.java:51)
at com.web.controllers.ajax.BasicAction.execute(BasicAction.java:27)
at com.web.HibernateServlet.doService(HibernateServlet.java:113)
at com.web.HibernateServlet.service(HibernateServlet.java:66)
at sun.reflect.GeneratedMethodAccessor200.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:695)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
at com.levitech.web.controllers.schedule.ScheduleList$$EnhancerByCGLIB$$4a7ae33e.service(<generated>)
at com.levitech.web.RequestDispatcher.service(RequestDispatcher.java:63)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:662)
17:56:46,090 DEBUG HibernateTransactionManager:753 - Initiating transaction commit
17:56:46,090 DEBUG HibernateTransactionManager:653 - Committing Hibernate transaction on Session [org.hibernate.impl.SessionImpl#6b204e88]
17:56:46,091 DEBUG HibernateTransactionManager:735 - Closing Hibernate Session [org.hibernate.impl.SessionImpl#6b204e88] after transaction
17:56:46,091 DEBUG SessionFactoryUtils:800 - Closing Hibernate Session
The model (ScheduleItem and User) and their hibernate mappings
public class ScheduleItem {
private Integer id;
....
private User user;
}
public class User {
private Integer id;
...
private String name;
}
<class
name="ScheduleItem"
table="schedule_item"
>
<cache usage="read-write"/>
<id
name="id"
type="integer"
column="id"
>
<generator class="identity" />
</id>
<many-to-one name="user" column="user_id" lazy="proxy"></many-to-one>
</class>
<class
name="ScheduleItem"
table="schedule_item"
>
<cache usage="read-write"/>
<id
name="id"
type="integer"
column="id"
>
<generator class="identity" />
</id>
<property name="name" column="name" type="string" />
</class>
I found the culprit. OpenSessionViewFilter is using a different session or sessionfactory.
Here is my Spring config and web.xml (What am I doing wrong?):
Part of web.xml:
<filter>
<filter-name>hibernateFilter</filter-name>
<filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class>
<init-param>
<param-name>sessionFactoryBeanName</param-name>
<param-value>sessionFactory</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>hibernateFilter</filter-name>
<url-pattern>/app/s/*</url-pattern>
</filter-mapping>
Part of Spring Config:
<bean id="myDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
<property name="driverClass" value="${db.driver}"/>
<property name="jdbcUrl" value="${db.url}"/>
<property name="user" value="${db.user}"/>
<property name="password" value="${db.pass}"/>
<!-- Pool properties -->
<property name="minPoolSize" value="5" />
<property name="maxPoolSize" value="100" />
<property name="acquireIncrement" value="5" />
<property name="maxStatements" value="200" />
<property name="idleConnectionTestPeriod" value="120" />
<property name="maxIdleTime" value="1800" />
</bean>
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource" ref="myDataSource"></property>
<property name="mappingLocations" value="classpath*:com/model/hbm/**/*.hbm.xml" />
<property name="hibernateProperties">
<value>
hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
hibernate.show_sql=true
hibernate.cache.region.factory_class=net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory
hibernate.cache.use_query_cache=true
hibernate.cache.use_second_level_cache=true
</value>
</property>
</bean>
<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory"/>
</bean>

Answer 1

From the log it looks like the session is still open when you get this exception. The other scenario in which you would get such an exception is if the row doesn't exist in the database.
User user = session.load(User.class, 1000); // Create a proxy
user.getName(); // This would throw lazy initialization exception if row doesn't exist
One more scenario that can lead to this is working with detached objects. If you fetched and stored the ScheduleItem as a HTTPSession variable. Retrieve it in another request and then try to access the proxy - it will result in the same exception. The session that was used to load the object has been closed. If that is the case you need to first reattach the object to the new session (merge, update or lock) before using it.

Answer 2

There are multiple solutions for your problem:
The easiest one is using Spring's OpenSessionInViewFilter. Just add this filter to your web.xml and configure it to filter your request.
This filter opens and closes Hibernate session in a filter, so during page rendering session will be open.
Some people believe that OpenSessionInViewFilter is against good design, and it mixes business logic into presentation tier. If you think so, fetch the referenced object in your query (for example by using join fetch in your HQLs).

Answer 3

You could try to:
Eagerly load the collection.
initialize the collection before leaving the collection by calling the respective getter method Hibernate.initialize(rtn.getUserRoles());
Thats basically two times the same approach depending on what works best in your setup. You are making sure to load the complete entity before leaving the session that way the entity can be detached from the old and then reatached to a new session without problems. What you are doing is initializing the proxy before leaving the session so that the collection is available for sure when you are out of a session context.