Hibernate - could not initialize proxy - no Session

Question

I'm using spring-mvc and hibernate session-factory.

@Controller
    |
    ->  @Service (@Transactional)
            |
            -> @Repository

I have 2 entities, User and Address.

User has a List<Address> with FetchType=LAZY.

If I add an Addressobject via user, within a @Controller, I get failed to lazily initialize a collection of role - could not initialize proxy - no Session exception.

But If I do this inside the service layer which is wrapped with @Transactional, operation works nicely.

I found out about hibernate proxies,...etc.

My question is, why @Controller cannot change an entity object which is retried from @Service layer. Because @Controller has no idea whether it is a hibernate proxy or anything else. To the @Controller it is just an object. So why I'm getting an error, if I change an entity object inside the @Controller. This is only happening to entity properties which are marked as FetchType=LAZY.

VGaur · Accepted Answer · 2015-02-02 03:39:49Z

2

When you choose a property to be lazily loaded, hibernate wraps those around a proxy having the session object in which the parent was fetched.

If you try to access the property after the session scope you will get this error.

Looks like your session is getting created and closed in service layer.

Implement OpenSessionInView Filter provided by spring, it will close the session after response being send.

answered Feb 2, 2015 at 3:39

VGaur

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2 Comments

user2172625 Over a year ago

But then there is a coupling between controller and dao?

VGaur Over a year ago

No, by implementing OpenSessionInViewFilter you are actually removing session management from your code thus separating your concerns which is good. Its a servlet filter which will manage hibernate session for you and you can write code without being worried about the hibernate session.

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