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Question From Mikalai Zaikin's material

 
J Johny Rufus
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Hi Folks,
Firstly I want to thank Mikalai Zaikin for his superb material.
Can someone please explain me ..
"
An enterprise bean instance can access resource managers in a transaction ONLY in the enterprise bean's methods in which there is a TRANSACTION CONTEXT available. An entity bean with container-managed persistence can access its persistent state in a transaction ONLY in the enterprise bean's methods in which there is a TRANSACTION CONTEXT available.
"
What can TRANSACTION CONTEXT here mean ???
Thanx in Advance
RUF SCJP 1.4
 
Mikalai Zaikin
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hi, Johny.
This not my material, this was taken from EJB spec.
My understanding of this excerpt is :
1. If you do anything with DB from bean's method - you *must* be in transaction context (somebody has to start transaction before you do anything with DB Connection, for example). Because in case method fails to commit, all your changes of DB should be rolled back as well.
2. About state access. If Bean is not in transaction, it's prohibited to call context.getRollbackOnly() or context.setRollbackOnly, because this makes no sense and will throw an exception -> bean will be removed by container. That's why you must be sure that bean' method is running in transaction, if you call any transaction-related method from EJB's context.
.... and that's why "Supports" transaction attribute can be a REAL PAIN, because there is no way to know for sure in which state (Tx or no Tx) method is running....
Cheers!
 
J Johny Rufus
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Thanx Mikalai,
So if i am not in a transaction but try to acccess a DB resource...will the code complain in deploy time ???
RUF
 
Mikalai Zaikin
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I'm afraid, it will complain runtime...
 
J Johny Rufus
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Thanx Mikalai. I can comprehend.
 
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