hibernate LazyInitializationException could not initialize proxy

Question

Here s one that has me perplexed  I m trying to implement a basic Hibernate DAO structure  but am having a problem   Here s the essential code   int startingCount   sfdao count    sfdao create  sf    SecurityFiling sf2   sfdao read  sf getId      sfdao delete  sf    int endingCount   sfdao count     assertTrue  startingCount    endingCount    assertTrue  sf getId   longValue      sf2 getId   longValue      assertTrue  sf getSfSubmissionType   equals  sf2 getSfSubmissionType        assertTrue  sf getSfTransactionNumber   equals  sf2 getSfTransactionNumber          It fails on the third assertTrue where it s trying to compare a value in sf to the corresponding value in sf2  Here s the exception   org hibernate LazyInitializationException  could not initialize proxy - no Session     at org hibernate proxy AbstractLazyInitializer initialize AbstractLazyInitializer java 86      at org hibernate proxy AbstractLazyInitializer getImplementation AbstractLazyInitializer java 140      at org hibernate proxy pojo javassist JavassistLazyInitializer invoke JavassistLazyInitializer java 190      at com freightgate domain SecurityFiling    javassist 7 getSfSubmissionType SecurityFiling    javassist 7 java      at com freightgate dao SecurityFilingTest test SecurityFilingTest java 73      at sun reflect NativeMethodAccessorImpl invoke0 Native Method      at sun reflect NativeMethodAccessorImpl invoke NativeMethodAccessorImpl java 39      at sun reflect DelegatingMethodAccessorImpl invoke DelegatingMethodAccessorImpl java 25      at com intellij rt execution junit JUnitStarter main JUnitStarter java 40

User · Answer

The problem is that you are trying to access a collection in an object that is detached. You need to re-attach the object before accessing the collection to the current session. You can do that through

session.update(object);

Using lazy=false is not a good solution because you are throwing away the Lazy Initialization feature of hibernate. When lazy=false, the collection is loaded in memory at the same time that the object is requested. This means that if we have a collection with 1000 items, they all will be loaded in memory, despite we are going to access them or not. And this is not good.

Please read this article where it explains the problem, the possible solutions and why is implemented this way. Also, to understand Sessions and Transactions you must read this other article.

User · Answer

If you using Spring and JPA annotation  the simpliest way to avoid problem with session in lazy initialize is replaysing    PersistenceContext      to   PersistenceContext type   PersistenceContextType EXTENDED

User · Answer

use Hibernate initialize for lazy field

User · Answer

It seems only your DAO are using session  Thus a new session is open then close for each call to a DAO method  Thus the execution of the program can be resumed as      open a session  get the number of entity and close the session int startingCount   sfdao count        open a session  create a new entity and close the session sfdao create  sf        open a session  read an entity and close the session SecurityFiling sf2   sfdao read  sf getId          open a session  delete an entity and close the session sfdao delete  sf     etc      By default  collection and association in an entity are lazy  they are loaded from the database on demand  Thus   sf getSfSubmissionType   equals  sf2 getSfSubmissionType      is throwing an exception because it request a new loading from the database  and the session associated with the loading of the entity has already been closed   There is two approaches to resolve this problem    create a session to enclosed all our code  Thus it would mean changing your DAO content to avoid opening a second session create a session then update  i e  reconnect  your entity to this session before the assertions   session update object

User · Answer

This generally means that the owning Hibernate session has already closed  You can do one of the following to fix it    whichever object creating this problem  use HibernateTemplate initialize object name  Use lazy false in your hbm files

User · Answer

We encountered this error as well  What we did to solve the issue is we added a lazy false in the Hibernate mapping file   It appears we had a class A that s inside a Session that loads another class B  We are trying to access the data on class B but this class B is detached from the session    In order for us to access this Class B  we had to specify in the class A s Hibernate mapping file the lazy false attribute  For example         lt many-to-one name  classA                    class  classB                   lazy  false  gt           lt column name  classb id                  sql-type  bigint 10                    not-null  true   gt       lt  many-to-one gt

User · Answer

The problem is that you are trying to access a collection in an object that is detached. You need to re-attach the object before accessing the collection to the current session. You can do that through

session.update(object);

Using lazy=false is not a good solution because you are throwing away the Lazy Initialization feature of hibernate. When lazy=false, the collection is loaded in memory at the same time that the object is requested. This means that if we have a collection with 1000 items, they all will be loaded in memory, despite we are going to access them or not. And this is not good.

Please read this article where it explains the problem, the possible solutions and why is implemented this way. Also, to understand Sessions and Transactions you must read this other article.

User · Answer

I think Piko means in his response that there is the hbm file  I have a file called Tax java  The mapping information are saved in the hbm   hibernate mapping  file  In the class tag there is a property called lazy  Set that property to true  The following hbm example shows a way to set the lazy property to false                                     id              If you are using Annotations instead look in the hibernate documenation  http   docs jboss org hibernate stable annotations reference en html single   I hope that helped

User · Answer

Okay  finally figured out where I was remiss  I was under the mistaken notion that I should wrap each DAO method in a transaction  Terribly wrong  I ve learned my lesson  I ve hauled all the transaction code from all the DAO methods and have set up transactions strictly at the application manager layer  This has totally solved all my problems  Data is properly lazy loaded as I need it  wrapped up and closed down once I do the commit   Life is goodly

User · Answer

If you are managing the Hibernate session manually  you may want to look into sessionFactory getCurrentSession   and associated docs here   http   www hibernate org hib docs v3 reference en html architecture-current-session html

User · Answer

By default  all one-to-many and many-to-many associations are fetched lazily upon being accessed for the first time   In your use case  you could overcome this issue by wrapping all DAO operations into one logical transaction   transactionTemplate execute new TransactionCallback lt Void gt           Override     public Void doInTransaction TransactionStatus transactionStatus             int startingCount   sfdao count             sfdao create  sf             SecurityFiling sf2   sfdao read  sf getId               sfdao delete  sf             int endingCount   sfdao count             assertTrue  startingCount    endingCount            assertTrue  sf getId   longValue      sf2 getId   longValue              assertTrue  sf getSfSubmissionType   equals  sf2 getSfSubmissionType                assertTrue  sf getSfTransactionNumber   equals  sf2 getSfTransactionNumber                 return null              Another option is to fetch all LAZY associations upon loading your entity  so that   SecurityFiling sf2   sfdao read  sf getId        should fetch the LAZY submissionType too   select sf from SecurityFiling sf left join fetch sf submissionType   This way  you eagerly fetch all lazy properties and you can access them after the Session gets closed too   You can fetch as many  one many -to-one associations and one   one many -to-many  List associations  because of running a Cartesian Product    To initialize multiple   one many -to-many   you should use Hibernate initialize collection   right after loading your root entity

User · Answer

if you are using Lazy loading your method must be annotated with    TransactionAttribute TransactionAttributeType REQUIRES NEW  for Stateless Session EJB

User · Answer

By default  all one-to-many and many-to-many associations are fetched lazily upon being accessed for the first time   In your use case  you could overcome this issue by wrapping all DAO operations into one logical transaction   transactionTemplate execute new TransactionCallback lt Void gt           Override     public Void doInTransaction TransactionStatus transactionStatus             int startingCount   sfdao count             sfdao create  sf             SecurityFiling sf2   sfdao read  sf getId               sfdao delete  sf             int endingCount   sfdao count             assertTrue  startingCount    endingCount            assertTrue  sf getId   longValue      sf2 getId   longValue              assertTrue  sf getSfSubmissionType   equals  sf2 getSfSubmissionType                assertTrue  sf getSfTransactionNumber   equals  sf2 getSfTransactionNumber                 return null              Another option is to fetch all LAZY associations upon loading your entity  so that   SecurityFiling sf2   sfdao read  sf getId        should fetch the LAZY submissionType too   select sf from SecurityFiling sf left join fetch sf submissionType   This way  you eagerly fetch all lazy properties and you can access them after the Session gets closed too   You can fetch as many  one many -to-one associations and one   one many -to-many  List associations  because of running a Cartesian Product    To initialize multiple   one many -to-many   you should use Hibernate initialize collection   right after loading your root entity

User · Answer

If you are managing the Hibernate session manually  you may want to look into sessionFactory getCurrentSession   and associated docs here   http   www hibernate org hib docs v3 reference en html architecture-current-session html

User · Answer

If you are using hibernate with JPA annotations then this will be useful  In your service class there should be a setter for entity manager with  PersistenceContext  change this to  PersistenceContext type   PersistenceContextType EXTENDED   Then you can access lazy property in any where

User · Answer

I think Piko means in his response that there is the hbm file  I have a file called Tax java  The mapping information are saved in the hbm   hibernate mapping  file  In the class tag there is a property called lazy  Set that property to true  The following hbm example shows a way to set the lazy property to false                                     id              If you are using Annotations instead look in the hibernate documenation  http   docs jboss org hibernate stable annotations reference en html single   I hope that helped

User · Answer

If you know about the impact of lazy false and still want to makes it as default  e g   for prototyping purposes   you can use any of the following    if you are using XML configuration  add default-lazy  false  to your  lt hibernate-mapping gt  element if you are using annotation configuration  add  Proxy lazy false  to your entity class es

User · Answer

If you are managing the Hibernate session manually  you may want to look into sessionFactory getCurrentSession   and associated docs here   http   www hibernate org hib docs v3 reference en html architecture-current-session html

User · Answer

Okay  finally figured out where I was remiss  I was under the mistaken notion that I should wrap each DAO method in a transaction  Terribly wrong  I ve learned my lesson  I ve hauled all the transaction code from all the DAO methods and have set up transactions strictly at the application manager layer  This has totally solved all my problems  Data is properly lazy loaded as I need it  wrapped up and closed down once I do the commit   Life is goodly

User · Answer

Okay  finally figured out where I was remiss  I was under the mistaken notion that I should wrap each DAO method in a transaction  Terribly wrong  I ve learned my lesson  I ve hauled all the transaction code from all the DAO methods and have set up transactions strictly at the application manager layer  This has totally solved all my problems  Data is properly lazy loaded as I need it  wrapped up and closed down once I do the commit   Life is goodly

User · Answer

if you are using Lazy loading your method must be annotated with    TransactionAttribute TransactionAttributeType REQUIRES NEW  for Stateless Session EJB

User · Answer

We encountered this error as well  What we did to solve the issue is we added a lazy false in the Hibernate mapping file   It appears we had a class A that s inside a Session that loads another class B  We are trying to access the data on class B but this class B is detached from the session    In order for us to access this Class B  we had to specify in the class A s Hibernate mapping file the lazy false attribute  For example         lt many-to-one name  classA                    class  classB                   lazy  false  gt           lt column name  classb id                  sql-type  bigint 10                    not-null  true   gt       lt  many-to-one gt

User · Answer

This generally means that the owning Hibernate session has already closed  You can do one of the following to fix it    whichever object creating this problem  use HibernateTemplate initialize object name  Use lazy false in your hbm files

User · Answer

If you are managing the Hibernate session manually  you may want to look into sessionFactory getCurrentSession   and associated docs here   http   www hibernate org hib docs v3 reference en html architecture-current-session html

User · Answer

See my article  I had the same problem - LazyInitializationException - and here s the answer I finally came up with  http   community jboss org wiki LazyInitializationExceptionovercome Setting lazy false is not the answer - it can load everything all at once  and that s not necessarily good  Example  1 record table A references  5 records table B references  25 records table C references  125 records table D     etc  This is but one example of what can go wrong  --Tim Sabin

User · Answer

See my article  I had the same problem - LazyInitializationException - and here s the answer I finally came up with  http   community jboss org wiki LazyInitializationExceptionovercome Setting lazy false is not the answer - it can load everything all at once  and that s not necessarily good  Example  1 record table A references  5 records table B references  25 records table C references  125 records table D     etc  This is but one example of what can go wrong  --Tim Sabin

User · Answer

This generally means that the owning Hibernate session has already closed  You can do one of the following to fix it    whichever object creating this problem  use HibernateTemplate initialize object name  Use lazy false in your hbm files

User · Answer

Okay  finally figured out where I was remiss  I was under the mistaken notion that I should wrap each DAO method in a transaction  Terribly wrong  I ve learned my lesson  I ve hauled all the transaction code from all the DAO methods and have set up transactions strictly at the application manager layer  This has totally solved all my problems  Data is properly lazy loaded as I need it  wrapped up and closed down once I do the commit   Life is goodly

User · Answer

If you are using hibernate with JPA annotations then this will be useful  In your service class there should be a setter for entity manager with  PersistenceContext  change this to  PersistenceContext type   PersistenceContextType EXTENDED   Then you can access lazy property in any where

User · Answer

use Hibernate initialize for lazy field

User · Answer

This generally means that the owning Hibernate session has already closed  You can do one of the following to fix it    whichever object creating this problem  use HibernateTemplate initialize object name  Use lazy false in your hbm files

User · Answer

If you using Spring and JPA annotation  the simpliest way to avoid problem with session in lazy initialize is replaysing    PersistenceContext      to   PersistenceContext type   PersistenceContextType EXTENDED

User · Answer

If you know about the impact of lazy false and still want to makes it as default  e g   for prototyping purposes   you can use any of the following    if you are using XML configuration  add default-lazy  false  to your  lt hibernate-mapping gt  element if you are using annotation configuration  add  Proxy lazy false  to your entity class es

User · Answer

It seems only your DAO are using session  Thus a new session is open then close for each call to a DAO method  Thus the execution of the program can be resumed as      open a session  get the number of entity and close the session int startingCount   sfdao count        open a session  create a new entity and close the session sfdao create  sf        open a session  read an entity and close the session SecurityFiling sf2   sfdao read  sf getId          open a session  delete an entity and close the session sfdao delete  sf     etc      By default  collection and association in an entity are lazy  they are loaded from the database on demand  Thus   sf getSfSubmissionType   equals  sf2 getSfSubmissionType      is throwing an exception because it request a new loading from the database  and the session associated with the loading of the entity has already been closed   There is two approaches to resolve this problem    create a session to enclosed all our code  Thus it would mean changing your DAO content to avoid opening a second session create a session then update  i e  reconnect  your entity to this session before the assertions   session update object

[hibernate] hibernate: LazyInitializationException: could not initialize proxy

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