Spring + Hibernate：无法初始化没有会话的代理-DAO上发生异常时该怎么办？

Question

I got could not initialize proxy no Session exception on my JSP pages.

Here is what I do;

There are DAOs for Hibernate. These are not special classes. They just have autowired instances of Hibernate SessionFactory. Yes I use pure Hibernate to do my DB access.

The functions on DAO classes are annotated with @Transactional(rollBackFor=Exception.class) and My spring configurations prepared accordingly. Also my entities/controllers are also configured with Annotations etc.

I dont have a seperate Service classes layer. My Services and DAOs are overlapped. they are same. If a Service class need to access DB they are just annotated with @Repository rather than @Service

Until this error, everything was working perfectly. (I have hundreds of classes/DAOs/entities etc)

Now, I need to call two DAO/Service functions at one of my controllers. I only call second DAO function when the first one throws an exception.

I need to throw exceptions based on some conditions to rollback the changes made with first DAO call. The second call just to show some information from DB to the user who entered wrong input.

I dont know why but the second DAO call is working, its gets classes from DB. then I forward this classes on to my Model attribute on my controllers so my JSPs can displays them.

But when my JSP pages tries to access attributes of these classes I got the could not initialize proxy no Session exception.

So here is my question, what should I do to avoid this errors.

Should I do something with hibernate transaction/session on the first DAO call? Because I do nothing. I just get a session and do get/save/update etc on it. I think @Transactional attribute will handle the transaction issues and @Repository attribute handles the session issues.

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I have already tried lazy/eager loading issue. I have already put OpenSessionInViewFilter filter on my configurations.

But none of them solved my problem.

Any advises/thoughts?

Answer 1

I solved the problem now :)

The problem was my misunderstanding of how Hibernate with Spring Framework works unfortunately :)

The exception occurs is in the JSP page when I was comparing the values of two different Hibernate proxies, each of them fetched from separate Hibernate sessions.

As I described in the question, In first DAO call I got a proxy, then, on second DAO call I got another proxy which is belongs to a different Hibernate sessions. Hence the first proxy is a detached hibernate proxy with a "closed session", I got this exception.

To solve this issue, if you can make try to make your detached proxies, persistent and then compare their values.

But I solved this issue by refactoring my code to not to open two different sessions for fetching values from DB.

Answer 2

Spring should wrap the service with @Transactional annotations with proxy wrapper that will initialize transactions, so you don't do that manually when you don't need to usemore than one transaction in one method.

In XML configuration you need to add <tx-annotation-driven /> in each XML file that declares beans with @Transactional annotations.